Dr. Anders: Professor Fischer-Hjalmars, you were, besides Madame Pullman, one of the first women in quantum chemistry. You published 90 papers some of which are still remembered in these days. I am very grateful that you consented to this interview here at Stockholm, on the beautiful island of Lidingö, fairly close to central Stockholm.

Prof. Fischer-Hjalmars: Yes.

A: By the way, you have this double name. And by chance I found a publication by a Hjalmars on meson physics (1a, 1b-1c)? Was that of your husband's?

F: He started there, yes.

A: And how did he continue?

F: He was a student of Oskar Klein, if you have heard that name (16). Oskar Klein was studying with Niels Bohr in Copenhagen for 10 years, I think. And when he was professor here in Stockholm from 1930 on, my husband did theoretical research with him on mesons and things like that. Later on my husband became professor at the Royal Institute of Technology, again here at Stockholm. There he had to teach mechanics, became interested in solids, solid states of a more complex nature where there are many different things involved. So he changed to the study of these things as well as to topics which were of special interest to the Royal Institute of Technology.

A: When did you marry? You must have married quite young.

F: No, on the contrary, fairly late. Because, you see, I did not even start in chemistry but in pharmacy. Since my family didn't have much money I had to earn my living myself. Because of a much shorter duration of studies in pharmacy at that time I started there. I was a pharmacy student for two years and then I took a first examination in 1939. Then the war started, lots of people had to do military service, they needed people in many places. I myself, for instance, had to travel all over the country, had to continue this for quite some time and was not at all in Stockholm.

During this time I decided that I would not continue with pharmacy. Due to my first examination in pharmacy I could always take jobs for shorter periods and earn money which I could use, in turn, for a longer period of studies because I had learned to live on small expenses. And I also decided to start at the University right away with, at first, chemistry since I knew, as a pharmacist, quite some chemistry.

Later on I also took physics and mathematics. We had in those days one course for normal studies, so to say, but then there were also the longer courses which one could take. They represented the more scientific part. That was for what we called magister, it's not quite the same as a Master in Science, so that I did in chemistry.

And then one day I got in contact with a person, not the professor - - well, the story goes like this: Imagine you have a benzene ring and then you have a chain - you have to synthesize this first. In addition you have one or two or three other components on this same benzene ring. Now, this person was looking for a good local anesthetic. In that research group I was at that particular time when we tried to chemically realize very many combinations of these constituents and finally found one that was pharmacologically very, very effective.

This was in 1943. We were a whole group of people working together with a person called Löfgren. Löfgren, at that time, was just licentiate. There was a very long way towards the Swedish doctoral degree, and the way to licentiate was a much shorter one. And he had got just that far in his career when he started his own research group with 8 or 10 students. I belonged to it, we worked quite hard, everybody was so very interested in this type of work. We tried very eagerly, as stated before, to synthesize a lot of homologues (2-5). When we had found something very interesting then we wanted to see which property it had, that was very important. So we did not only make the synthesis, we also tried it on our own nerves to see how it worked, we tested everything on our fingertips, despite the fact that we had a biologist in our group. So these were very active years in that group.

And then finally in 1943 (5a, 5b) we found THE substance we were looking for. As a consequence Löfgren then looked around for somebody who could produce it on a larger scale, to commercialize it - -

Here is the first paper with him. And then there are several more. Löfgren, he was the leader. First he approached several companies who produced medicines and they were not interested. But then he found one - Astra - and if you look at this (Prof. F.-H. shows a current medicine package of Xylocaine made by the Astra pharmaceutical company of Sweden). In 1948 Astra started producing this - our compound - and it is still one of their leading products. Astra was a very small company before, but on account of this local anesthetic they grew and became important.

So I was in the group when Xylocaine was found. I think it is rather remarkable that this group was able to produce a medicine that would continue to survive a period of 50 years! I mean, quite often there are new pharmaceutical substances which will have a commercial life of 5 or 10 years - but this one has survived 50 years! Before Xylocaine there was something called Novocaine but that just disappeared as soon as this one came out. In the United States, by the way, Xylocaine is known as Lidocaine.

A: How old were you then - by the way, when are you born?

F: In 1918. In this group I worked from 1942 to 1945 about, so I was in the twenties. Because I finished school when I was 19, and then I started with pharmacy and that took me three full years. Then when I came to the University I also started studying not only chemistry but also mathematics and physics and that also took time. But I had my examination in '44 and then I was 26 years old. I already had started in the Löfgren group and then I continued some time afterwards.

And then it was suggested that I should try to measure the dipole moments of all these substances which we had made in the Löfgren group (6-8). But in those days there were no commercially available devices for measuring dipole moments. So I had first to find somebody who would help me to construct such a unit, which was in function similar to a radio apparatus, measuring dipole moments via changes in the capacity of an oscillating circuit (9). And this was during the war, as you understand, so one couldn't get in contact with people in other countries. We had to stay in Sweden and see what could be done. It was only after the war that I could contact Norwegian researchers and work in Norway where they had measured dipole moments before.

A: The measurement with capacitors and AC current and all that?

F: Well, of course, the methods used in the forties were not the same as today (10). But at least there were people who had built apparatus and then we tried to do the same in Stockholm. But I couldn't build the apparatus myself but I found a person who was clever on that kind of thing, so he had to build the apparatus when I knew what kind of apparatus I needed.

So then I started making dipole moment measurements and then we tried to find some property why these dipole moments might be important. I wanted to understand things better and, you see, since Löfgren couldn't provide me with sufficient money to live on I had to have other kinds of jobs. So I started to work with Hans von Euler , who was a Nobel prize laureate (15) which he, I think, received around 1930. In my time he was already excused from the ordinary duties of a professor so he could concentrate on his research. And, of course, as a Nobel laureate he could find some money resources. I could be an assistant to him for a while, and since I had learned some spectroscopy and physics I could use that also as his assistant.

Under these improved conditions I could also continue the measurements of the dipole moments even while I was an assistant to Euler at the same time (11-13). In these days it was not possible to obtain money from any funds just for studying. Everybody who didn't have rich parents had to earn the money him- or herself.

A: How long have you been assistant.

F: Of Euler? Not very long, maybe for one year and a half, something like that. Due to my curiosity I wanted to know more about the molecules than what was being taught in chemistry, I wanted to use other methods as well. I had read the basic part of physics, I knew that. But then I wanted Theoretical Physics as well {laughing, I.'s n.}. So then I started studying with Oskar Klein. But in the beginning I couldn't earn any money there, I could just learn. And I was there, I think, until 1948 for learning. But then I had taken the first degrees in Theoretical Physics, and then I could become an assistant to him, instead of von Euler.

A: I find it so amazing: a person studying not even Pharmacy and then Organic Chemistry - then in addition also Theoretical Physics. You were just curious?

F: Yes, I wanted to understand better what's going on {laughing, I.'s n.}., what is happening in a molecule.

A: This is something which is my main theme in this historical context: how did the chemists arrive 'at the quantum'. That makes your case is so very interesting. On the other hand you must have been a very smart woman learning all this. It's not easy, you also had a lack of mathematics of course. You not only had to study Theoretical Physics but ....

F: Yes, I had a basic in mathematics that was necessary, of course. But there I didn't take very big courses, I took the normal courses, so to say. But in Theoretical Physics I took first the normal courses but then I continued with the more severe ones.

A: Did it come easily to you or -?

F: Well, I think it was - this to start with Theoretical Physics, there were not very many people there. And Oskar Klein was a very broad-minded person. He himself was interested in many things not only in Theoretical Physics as such. He also had some work together with biologists, for instance. And it was also he himself who established these kinds of contacts. He understood that I wanted to get a deeper understanding of the properties of molecules.

So first I had the basic courses and things there. Before 1945, when the war was still going on, we had no possibility to go to other places, contact other people. But afterwards foreigner began visiting Klein, because he knew of course everybody: he knew Pauli , he knew of course Bohr , he knew everybody in Theoretical Physics in the different places. So, therefore people came to Stockholm and gave lectures. They came to visit Oskar Klein, Lise Meitner had come to Stockholm during the war, because she had to leave Germany. And she came to M. Siegbahn's Institute in 1940. But then she came often and gave also lectures with us. And we had seminars where she talked about the nuclear problems and so on. And then after war then Pauli came and gave a lecture and Bohr was there - all of them came!

A: Where you the only woman in this field?

F: Lise Meitner {laughing heartily, I.'s n.}.

A: But no more?

F: Yes, after some time I got a student with me Barbro Grabe (14). And then later on there came more and more female students. It seems they found that if one woman could do it why not another. So then I had several students who were women.

A: You had your interests in Organic Chemistry, dipole moments. You learned Theoretical Physics. What was the idea that brought you to Lithium hydride?

F: Yes, you see, then I finally decided that I had to study with somebody who was an expert in Quantum Chemistry. So then in 1948 there was a meeting in Paris -

A: Yes, the famous meeting, where Mulliken had this article all in French.

F: Yes, that's right. And lots of people came there. Well, there was a professor in Uppsala called Tiselius, he was also a Nobel laureate (17). And he, after the war, had started together with other researchers something called forskningsråd (Research Council). This organization, the chairman being Tiselius, tried to distribute money to people who had shown some interesting perspectives and who were worth further sponsoring so that they could continue.

Already while working with Löfgren it so happened that we went to see Tiselius . I met Tiselius there together with Löfgren and some others, and we tried to get money to Löfgren's project. Tiselius became interested in my personal progress as well. He indicated that if I could go to that conference in Paris and find somebody with whom I could stay for some time to learn more, then he would give me money to go to Paris and then also to continue afterwards. And there I met Charles Coulson (18). And what Tiselius said was: you can choose whom you find and who is the best for you, but please you should not choose Linus Pauling ; because he has so very many people around him so he will never have time to really help you. So find somebody else. So I approached Charles Coulson who agreed to take me; he was a very kind and helpful person.

A: How do you remember him?

F: Oh, I think, he was a personality, he was extraordinarily friendly and helpful and did everything he could for everybody. I think he was a fantastic person; I got a very good impression of him already right there in Paris. With him there was a student of Charles Coulson, Longuet-Higgins (19), he was, I think, 18 or something like that. He looked like a very young boy. I myself - it was 1948 - then I was 30, but he was very young. But he had already done very important work with Charles Coulson; it impressed me greatly that Coulson had, together with this very young boy, already produced very important things. So I thought that this would be a very good idea to go to London, it was not as far as going to the United States.

A: One didn't fly in those day so much maybe? One had to take the ship.

F: No, yes, because there I should tell you that both my parents were Danish. They had come to Sweden after some time but my father had already work here in Sweden before they married. My mother had been a teacher in an ordinary school before they married. But after the marriage when she came here to Sweden she couldn't continue teaching. And then - that was in 1914 that they were married - in 1916 they bought this house in which we are sitting just now.

But in those days we didn't have very much money and my parents and we children lived upstairs since this lower part of the house was rented to someone else who could pay for it. So I have been growing up in this building. Then of course, when I become 20 or so I had to move around and was not living here all the time. Yet our parents kept the house until they died, that was in the seventies. Then we thought that this position of the house - you see in those days there were no houses behind it - was a very nice one and we decided not to sell it. So now my sister is living upstairs, and my husband and I are here downstairs and over there is a small cottage as well. Because you may see that we have quite some books here - and these are not the scientific books, those are over there {Pointing to a medium-sized wooden cottage next to the house - I.'s n.}. So we need a lot of space. All of us children were growing up here.

Therefore it was very natural for me to got by way of Denmark to go to England because from Esbjerg you can go to London by boat. And, more over, I had an uncle, my mother's brother, who was living in London. That was very comforting. Furthermore, for certain periods my father did do so many different things and he was travelling a lot. So in this period the rest of the family had for some time moved back to Denmark, we stayed for about one year in Denmark, at home we always spoke Danish, so Danish was my first language. And even now my sister and I always use Danish when talking to one another.

And my brother is living in Nacka, a suburb of Stockholm. My eldest sister wanted to be a missionary, but first she wanted to be Danish. Because, just before the second world war, we had to decide whether we wanted to be Swedish or not Swedish. So most of us decided to be Swedish because we wanted to stay here, that was in 1938. You know, when things - yes, you were not ... {laughing, I.'s n.}, you do not know how it was.

Yes, it was important to know who were really Swedish and who were not. So then my eldest sister moved definitely to Denmark, in fact, she moved earlier, she moved already in 1934 or 1935, and then she became more and more Danish, so she got her education in Denmark and she was a school teacher in Denmark for some years. There she came in contact with people going abroad to spread Christianity and then decided that she wanted to do that. So she started studying theology at the University. In the course of this education she had to go to England to learn English because in every country you should go to you must know English - it was in Pakistan where she then wound up.

Therefore we were together in England for half a year. I had to study quantum chemistry and she had to learn English. So it was quite practical for both of us to have an uncle right there in England. That was in 1948, the situation in England not being very good right after the war. People had not very much and so it was very good to have someone whom one knew and where one could go to and so on.

And Charles Coulson was also very interested in what my sister was going to do.

A: Yes, I read this - Christianity was a big point for him.

F: Yes, he traveled around the world and talked about Christianity, in various places. So I think, ...

A: So he liked the two Fischer sisters.

F: You see, I had only money for a short period with Charles Coulson. So I stayed there about half a year.

A: Oh, that's not long.

F: No, that's not long. But I was happy to have it. And there I met many people. He had a group of students around him, people of many different countries.

A: Whom do you remember?

F: Norman March, for instance (21). He is now professor in Oxford after Charles Coulson.

A: And how do you remember Longuet-Higgins?

F: Well, he was very independent in those days, when I came there. He had done a paper together with Charles Coulson, but he worked normally at Cambridge so I didn't see so much of him.

A: Whom else do you recall?

F: Yes, McWeeny (22). I met him too. He is in Italy now.

A: Yes, in Pisa. He had married a sister of Del Re (23). How do you remember McWeeny, all I heard of him that he was a easy-go-lucky fellow.

F: Yes, he was always good spirited. So that was very interesting.

A: And how could you keep up with the physicists? Did you feel equal to them with respect to theoretical physics and mathematics?

F: Well, they were of course also interested in chemistry. And Charles Coulson and I made a paper together while I was there(20). That was about the hydrogen molecule, we looked at the excited states of the hydrogen molecule. So there I had a small molecule instead of these big ones. And then I thought, in the organic molecules I was particularly interested in, there were not only atoms of the same kind, I mean not only carbon and so on. There were many others as well so it would be good to study the detailed properties of a molecule with two different atoms. And then the simplest to choose is the lithium hydride.

A: I had already wondered how you had arrived at this.

F: Yes, because I wanted to look at more complex systems. But I understood that I could not begin with the very complex ones right away. I had therefore to look how one could find out the differences between atoms, their properties and so on. And that was the reason why I started with lithium hydride.

A: And then, in the third paper of this series, you already used the molecular orbital treatment on some saturated and unsaturated ethers?

F: Yes, and that was because I had - I said that I went to Oslo, and there they had studied many such compounds experimentally.

A: The dipole moments?

F: Yes, and other things. So, I got a good background. These ethers were simpler than Xylocaine which is a much more complex molecule. I knew many of the properties that had been studied in Norway. So I tried to see what the calculations could reproduce, then to think and to compare, for I thought that it was always very important to have experiments to compare with, and not only just to sit down and do some reality-independent calculations. I always thought that there should be experiments, so as to have a check on the meaning in the kind of calculation one was doing.

A: That's what I never liked about Quantum Chemistry. There were many theories how to calculate things, beautiful maybe. But then how would that theory apply to different molecules? Well, if one comes from the chemistry side, it's the other way around, one has the spectra and so on.

But you always published in parallel, I found that very clever, in the Archiv för Fysik, but that maybe nobody read, and so you published in Nature as well. Did you have any problems getting your papers into Nature? Did you get any help from Coulson in this respect?

F: Yes, then I should also tell you, that P.-O. Löwdin and I, it was P.-O. Löwdin's idea ---.

You see P.-O. Löwdin (28) started in Uppsala and I was in Stockholm, and when I became interested in quantum chemistry he was in the United States staying with Slater (29) for several years. So therefore, I didn't meet him until I took my doctor degree in 1952 - which in Sweden is a rather big thing,. I also had a series of papers behind me and that was the first time I met Löwdin, that was when I had to present my doctoral thesis. So I mean, I never could study with him, I was already independent, so to say.

But then we had of course kept contact all the time, he has always been travelling a lot, and established lots of activities all over {laughing, I.'s n.}. But anyway, in 1953/1954, no, I think it was 1954, I took my doctor degree in 1952 and so I think it was in 1954, when he suggested that we should make a Quantum Chemistry meeting right here in Sweden and that we should have half of it in Stockholm and half of it in Uppsala. So us two, together, organized a meeting and we invited people. I don't know how we were able to find so many, of course Coulson came, and many others.

A: Can you mention a few who came?

F: Yes, Mulliken was there, and then also Boys (30). People said: "How did you manage to get Boys here, he is no more going to any meetings anywhere, he would just stay in Cambridge and continue his own, and then he came here to you?" Everybody was so very astonished, but we invited him and he came {laughing, I.'s n.}.

A: Was Boys a little bit withdrawn?

F: He had started already his Gaussians in 1952. He walked by himself and I don't think - yes, he had Handy working with him.

A: Handy?

F: Yes, in the 1950's I read some papers by Boys and Handy but I did not meet Handy. And when I was with Coulson in 1948 I visited Cambridge and I was allowed to visit Boys. So he showed me around in his laboratory and he had of course the calculating machines, which were in those days enormous. I mean, it was not something you had on your table, there were rooms filled up with the machinery. He was very nice, but I was a complete beginner but nevertheless he was very kind towards me and showed me these things. And then we tried to invite him and he came to Stockholm, so I think, that was very nice.

A: Is this meeting reported somewhere?

F: Yes, only in a Swedish journal. I don't think that it is published elsewhere. I'm not sure, if I have it here, perhaps I have it or perhaps I haven't, I don't remember.

And then I must tell you, that when I was in Paris of course I met the Pullmans (60). I had heard about the Pullmans earlier, because there was a person working with Klein, called Svartholm (32) and he was for a while rather interested in what the Pullmans were doing. And then he had a co-worker, they also made some calculations using the Pullman's methods. Those had been made in Stockholm before I started with Klein. That was, while I still was in the chemical laboratory. There I heard about these things and so this gave me interest.

A: I know Svartholm's work because Madame Pullman said that this first gave her the idea to do something in that direction.

F: Yes, he died, I think, a month or two ago, but he was also a person who didn't have much contact with people, he was like Boys.

A: Withdrawn?

F: Yes, but he was professor in Gothenburg for many, many years, so he had left Stockholm rather early, 1947 or thereabouts, I think. Since then he had been in Gothenburg all the time.

But I had heard about his first papers already in 1943, and when I came to Klein in 1946/1947, a student of Svartholm's was with Klein, and he told me about the calculations. But Svartholm himself had already turned to Gothenburg.

A: Do you remember any other persons of the symposium of Stockholm and Uppsala?

F: At least, we thought that I should invite Coulson and P.-O. Löwdin should invite Slater and then we should perhaps invite five or ten people, but I think there were about 50 people when it finished.

Yes, there was one - I'm forgetting names, that's bad - from Texas, who's name I should know, I met him many, many times, he came to Stockholm and then after ten months later or so, he himself organized a meeting in Houston, Texas (61). And then I was invited to go there, I went to Texas and there I met very many people. So that way I got very many different contacts.

A: And then at some time you married?

F: Yes, that was immediately after I had taken the doctoral degree, in 1952, when we were married. Because I in fact had so many things to do, - I took both licentiate in Chemistry and in Theoretical Physics.

A: Did you had any children?

F: No, we didn't. I was 34, when we married, so I was rather old.

Well, I had a student who began working with me and who then had two children. She later continued work with me and by and by took the doctoral degree. Her name was Marianne Sundbom. After the degree she continued very actively for some years (33) but got cancer and died when she was fifty, so that was very sad.

Another one of my students, Anita Henriksson-Enflo, came from Finland to our group in the seventies, and found her husband here in Stockholm. When she by and by had three children, she first continued part-time with quantum chemistry. Later on she worked full-time again (34). When she took her doctoral degree, I had conventially retired from my chair some years earlier. I tried to find some money for her since she was very eager to continue with quantum chemistry. But then it was said that what she had done was very good, but with regard to her age she had too few papers. And I said, but she has three children, but they didn't care about it. So it was very difficult, I couldn't manage to let her continue, although she wanted to. So she had to take an other kind of work. This is an example and a sad one.

Well, there are people who can manage children and nevertheless do lots of science and that is enormous, I think that this was very hard. Well, Anita says, she has had very many interesting works nevertheless, and she hopes to follow what it is happening in Quantum Chemistry and continues to make follow-ups.

A: And then you became professor of Theoretical Physics fairly fast?

F: Yes. Well, that was in 1963. It was after Klein had retired, and then first I had a position at the Royal Institute of Technology. My husband became professor there in 1956, I think it was, yes. And then I became associate professor in 1959 at the Royal Institute of Technology and stayed there and after four years I became professor at the University after Oskar Klein.

A: How did the physicists like it, that a woman and then a quantum chemist ...

F: Yes. Well, of course there were many different opinions, because there were others who wanted another person in this position. But after all - I got it.

A: You had many papers out by that time. So, you always remained faithful to semiempirical methods. Later you have did ab initio calculations as well. But most of your time you have been with the semiempirical methods and always remained. You started with the aniline paper ...

F: Yes, because this is a part of the Xylocaine. With Xylocaine you have a longer side chain and there at the aniline I could study what was important here, that when you have two methyl groups in ortho position then you have this property that it is a local anesthetic. If you move one of the methyl groups one step further then the properties will be much weaker, it's only when both of them are in the ortho position. And this means, if you try to look upon which structure you get, it is not planar any more, when there are two methyl groups in ortho position. And this means that the p -electrons cannot move over the whole molecule, it's no ring. So these ortho positions are so important for so many properties.

A: That is interesting. If I recall correctly: modify this structure a little and you arrive at ecstasy. You started to use Pariser-Parr-Pople method fairly often.

F: Yes, but then we tried to improve that. Because in the PPP method - by the way for instance I stayed for some time, about half a year, in the sixties with Parr. That was very nice. My husband together with his mother and I started to visit their family in Oregon, where my mother-in-law had a brother living there with his family. My father-in-law had died, but my mother-in-law was still rather lively, and she would very much like to visit her brother in Oregon; so the three of us went there. And then my husband went back with his mother to Sweden but I had arranged that I should stay with Parr for some months. So I stayed there I think for four months.

A: And at that time he was still using the PPP method?

F: Yes, but I didn't have a paper with Parr, I wasn't there so long. I mean I had earlier been very interested and I thought it would be interesting to meet people in his group and so on. But I made some papers afterwards, but it was nothing about what we had done together.

A: You said, you improved the method.

F: Yes, there were parameters of course on everything. And in the original method the one center parameter was independent of the neighbors, in the PPP method. So for carbon atoms you had always one Wc and Wo and so on. But we found - I made an analysis because the PPP method tells that there should be orthogonality between the various orbitals of the different centers. And then Löwdin had worked with methods where he had studied the overlapped integral -

A: .

F: Yes. And then I made a detailed analysis of this - 1965, Journal of Chemical Physics, Number 42 - there I made a series expansion with S being different (35). So I first took only S to the first degree and then the second degree and then the third degree. But then I stopped at the second degree and saw which kind of pattern you got in that case and found out that the W, the one center, is not independent of the surrounding. So you should have different values, you should add something to the Wc, for a certain kind of surrounding atoms and something else for a different one.

I had said already that I was in Norway to study the dipole moments. Later on my husband and I made several holiday visits to Norway, my husband liked to stay in the Trondheim region and I went with him. On this occasion I met people who were doing quantum chemistry there. And there was a young student called Skancke who then came to me in Stockholm and stayed there some years and took his degree in Stockholm and now he is professor in Tromsö in the far north {laughing, I.'s n.}. Skancke had a very good experimental background, and he had started the experimental research. But he was also interested in quantum chemistry. Therefore, he came to Stockholm to join my group.

Roos and Skancke together studied several hydrocarbon atoms and showed which parameters would be useful there. With these modified parameters they got a very good agreement with the experiments (36). I had made the analysis but then they had made the applications on these hydrocarbons. And then in our group we continued along the same way - they had done this for the hydrocarbons and later Marianne Sundbom and I did those containing nitrogen, others did the ones with oxygen and so on.

A: So you had met Hall - - (37)

Fischer-Hjalmars in 1955 at the Austin Meeting.

F: In Austin, Texas, in 1955. And then I met him again in Japan when I was there and so on. I met George Hall at many different occasions and I always find a pleasure talking with him. But we haven't worked together or so - it's just he is a sympathetic person. He is not dominating in any way, but he is very well informed and inventive and it was always very nice to talk with him. So I will recommend you to contact him, if you are going to England. A: And you went also to Austin, Texas for some longer time? F: No, only for a meeting. You see, then again, I had this contact with Tiselius in Uppsala and he also said that I should take the opportunity to visit different places, to meet people. So I traveled and made short visits. I met professor Slater for the first time. I went to several places to get acquainted with people. I was always received very friendly. I am grateful to Tiselius who had possibilities to assist me, that was very helpful for me. A: In your earlier papers there were several on the zero differential overlap, one in Quantum Chemistry with Sinanoglu (38). F: Yes, I participated in an interesting meeting that Sinanoglu organized in Istanbul. A: How did you come to the zero differential overlap problem? You parametrized your semiempirical method and then on day you started to wonder about NDO (59) and you looked at it critically? And you went as far as to generalize Hückel, on the side of the NDO problem. Did that come from your work with organic chemistry?

F: I think, that it is perhaps because I was so familiar with the experimental part, I knew about the various properties so well. There are differences in various properties in the spectra and the dipole moments. So, I thought, if one could find methods that would really reflect the experimental knowledge as correctly as possible, it would be very interesting. I wanted to get the better understanding of the whole thing, I always tried to find out as many properties as possible. I always studied the literature very carefully, tried to get in contact with people who were making measurements. We had in Stockholm a very good group in spectroscopy, in physics, it was Lagerqvist (39) who had a very close contact with Herzberg who came to visit our lab and so on. So there were excellent measurements of spectra in the physics department.

A: And then there was Siegbahn doing his photoelectron spectroscopy... (40)

F: Yes, but it was, I think, perhaps mainly this physics department and their measurements, where I had closer contact with them. There was one professor Hulthén, he retired perhaps 1958. Then Lagerqvist took over. I knew him very well and he was professor there for a very long time and I knew his work very well and we had many discussions. We had our offices in the same building and so we met frequently and had very much close contact with the physics department.

A: Did you feel discriminated by the people who always ran after newer methods? Today there are those who think well of semiempirical methods and its parametrizations and then there are those others, the ab initio people. How did you feel it in those days?

F: Well, I will first say that all methods are more or less semiempirical {stated in a much louder, determinate fashion. I's. n.}. Because: You can never really, by theory, describe what is going on, in detail! You must always make some simplifications! And then you have to choose which simplification you actually want to make! But you can never produce a complete picture of what is happening.

A: But the ab initio .....

F: {interrupting fiercely the question of A., all underlined words strongly pronounced; I's n.} It is called ab initio, it is not 'ab - initio'. I mean, as soon as you have more than three particles in a system it is impossible to make a correct calculation of all the properties. You must always leave something out. And then you have to make your choice. So therefore this 'ab initio' is not ab initio! One must only look upon it that it is going different ways, because you always will have to stop somewhere, you can never come to the end. I think one has really to realize that ones possibility is always limited. Nature is much, much more complicated than we can penetrate. And we must understand that we are only trying to make a rough picture of the whole thing and then it all depends on which color you want to give to that thing. But it can never be the true description of what is behind.

A: Apparently Löwdin has written an article on truth in natural sciences lately (41). Thiel in Mühlheim - he uses semiempirical methods on very big molecules (42).

F: Yes, maybe it is more interesting to look upon a bigger system with a simpler method then try to do everything as well as one can in a very small system, since you must realize that you never will do it completely anyway.

A: And you had your oxygen parametrized and nitrogen, you worked on bromine, fluorine (43). And then you went into metals and biology (44).

F: Yes, metals. Because we always realized that metal compounds are very important in life and also in industry. But then - one always had to find money, this was always a problem. We came across the Industrial Welfare Foundation, a Swedish organization that analyzed what problems arise when working in different milieus. And how can the different metals be positive or negative for a system. So they wanted people to study the effects of the metals and they received some fund from where they would give.

And then it so happened that one of our group - his father was organizing there - so at a very early stage we were aware that they had some money to distribute {laughing, I.'s n.}. And therefore we found that this would interest us very much to study the different metals. So we started both to find information about different metals in biological systems, and as to how people would behave, I mean, how they will react on metals in industrial environments.

And then we were a group, I was the leader, but Marianne Sundbom had a very important part in this and those were, as turned out later, her last seven years in life. It is very sad that she couldn't live longer. There were very many people who wanted to work with her, she got a group of people together who started to work on the metal problems. I was also a little bit involved, but she was really the one who was guiding. She was a fascinating person who established very good contacts with various people. Her students started collecting information on the different metals and they wrote reports which turned out to be excellent reports. Five years after her death people from the medical department came to me and asked whether I had a report on this or on that, because these reports were known to be the best to be encountered.

Yet Marianne Sundbom was really the person behind all this and who did the practical work. She had a very important impact on these things. During this work we tried to find simplified calculatory systems that could represent these molecules which were so important for the living matter and then to find parameters to enable calculations on them.

And there again - we couldn't do anything but the semiempirical methods in this context. Somewhat later Björn Roos, (I already mentioned Roos and Skancke), started with copper and found a way to parametrize copper (45). Copper is comparatively simple since there is just one orbital open. When you go on to iron then you really have a problem. But anyway: he started with copper, Marianne Sundbom and I took up iron afterwards (46) and then we took series of other metals as well.

A: The copper investigations, when was this?

F: That was Roos around 1967 (45).

A: And yours was "Metals in biology, an attempt at classification", 1982 (48)?

F: Yes, that was together with Anita Enflo. But there exists an earlier one as well, here I have it, a review so to say, number 51, "Semiempirical studies on metal complex of biological importance" (48). And there I have the whole group with their names: Grabe, Roos, Skancke, Sundbom. So I think that this was in 1967 (45).

And then came the nitrogen - but there it is a metal complex. And then we had to do both this organic part of it as well as possible with the metal in it. Seybold was with me some time. But then I think it were mainly the other people of my research group who made the first publications of these metal complexes. When Marianne Sundbom had become very ill I took over some of the work which she had been doing.

So then I myself went into it, but I thought she had really done so much, so I wanted to leave, so to say, the field for her. I mean, I think it's very important that a professor should not always want to be cited on a paper just because he was the one who had started it. The other members of a research group should have a chance to be by themselves. Klein was excellent with that, I know that not all professors will do that way. But Klein never put his name on a paper when he didn't have worked very much himself. Not, because he had given the idea, no, he should have worked on it, too. And I learned from him and I felt this is the right way to do it.

Later I had a paper 1974 with Margareta Blomberg and Anita Henriksson Enflo on "Lithium and Beryllium in biological systems", that was in 1979/1980 (44c) - that is when Marianne became more and more ill. But there in the beginning it was Sundbom who was the main author in those papers. Roos was specially occupied with copper - but for the others it was Marianne Sundbom who worked on them. So then, when her health didn't give her no longer any possibility, I had to take over the supervision of the project concerning the metals.

Around 1982/1983 there came our publications about the iron complexes and there Holmgren and Henriksson Enflo published with me (46a).

And I must point out again: there, in these metal complexes, one had to make a choice which way one should try. One can never give a full description, one must decide what one wants to do.

A: Could you parametrize a metal for many compounds or just for one group of homologues?

F: Well, when there is a similar kind of surrounding then one could use those parameters.

A: Around this time, or maybe a little later, Jug in Hannover started his SINDO calculations (53). He said in an interview that he considered the higher metals as very difficult to deal with.

F: Yes, because they are so important in biology and that is what was leading us. And just because one wanted to know how these various metals can be useful or just disturb the surrounding. It was for these reasons that we wanted to study such metals. Metals which were of importance in industry as well as for the human body of course. Of course we knew that sodium and potassium were not so interesting in this context, one must look at those at the other end of the row. I mean, sodium is always ionic, so there one does not need to look upon it that way. But when considering complex compounds, then of course titanium e.g. may be interesting. And although zinc is comparatively simple from the quantum chemistry point of view, it turns out to be very interesting biologically, so we made calculations on zinc complexes also.

A: Now to the problem of agreement. How did these calculations and the physical properties coincide? In the early times you had the dipole moments, now there are spectra. Did you fit your parameters until they reproduced the spectra correctly?

F: Well, the spectra were important for deciding which parameters to use.

A: What approach did you actually use in setting the parameter values, was it empirical or was it intuition? Take copper as an example: how did you or Roos go about to parametrize it? By what way did you arrive at your parameters?

F: Well, one must of course look upon which orbitals are filled or unfilled and start from the experimental information about the metals. And then find the parameters that will give reasonably good values.

A: I see, guided by orbital considerations.

F: And then what we did: If we had a complex, for instance with nitrogen compounds, around that iron, and then carbon, oxygen in between and so on - we didn't look upon the whole complex neutral or 1+ or 2+, we looked upon many different charges. We did have both positive and negative complexes, because iron of course will be Fe3+ normally, or Fe2+. But the whole complex might be different. So it could be neutral or it might even be negative. And we studied the stability of the whole series and not just with one charge on the whole complex. So we were changing the charge all the time, and there we found that in many of those cases it was 1- or 2- which were the most stable of them. So one might expect that such complexes would play an important role in biology for instance.

Because of this we didn't assume anything before we started. We thought of course, that it should be Fe2+ for instance, that should be the starting point. But then we found that when we added electrons, the whole system became more stable. And this means, that such a system will have a surrounding that will interact very much with it.

A: This is a chemist's point of view and sometimes pure theoreticians look at such a procedure quite doubtfully. Researchers who then, on the other hand, use their theories only on a fairly limited range of real and important compounds.

F: Yes, and just for that very reason we started by looking upon which kind of systems are important for biology in particular. We especially wanted to find out the biological effects since this means so much in so many contexts. And then we wanted to find simplifications that we could handle in our calculations and find out the properties of this.

A: Would that connect back to your first work? I found you hydrogen bridge idea a very courageous article. It was very, very early when you had that idea of trying to calculate the hydrogen bridge. Wasn't this in the fifties already (25-27)?

F: Yes, because I knew from experiments how important the hydrogen bridges are and I knew that they are so essential for everything here on this earth. I mean the whole earth is depending on hydrogen bridges. So that is why I was so interested in hydrogen bridges.

A: And then you continued that idea, is that true to maintain, throughout all the years and picked it up in the end again with the DNA (55).

F: Yes, I mean, I had a student, Hans Holmgren, and I had asked him to look closer at this hydrogen bridge. He himself was very interested in hydrogen bridges. But then he died in an accident in 1996, he was 52 years old. But then - such people just disappear, that is very sad but such is life.

But anyway, I never gave up the hydrogen bridge.

A: At one time you went to Pullman's Jerusalem Symposia. Pullman, in his later years, was very interested in those biological systems. Did you watch the work Pullmans were doing closely?

F: Yes, I tried to follow what they did. Enflo and I made an overview article and I'm looking for that. {Prof. Fischer is looking for some paper in her list of publications, I's. n. }. It is number 81, "Metals in biology", in Advances in Quantum Chemistry, 1982. There are many metals on which we had looked upon (56).

Then from 1982 on we began changing the structure of the system. In the beginning we had a fixed, most reasonable system. But now we started looking whether one could modify the structure, we put different charges onto it: different structures, different charges. There are papers on this as well (57): I think that Holmgren had also started on this but never could finish it because of his accident.

So, we had such ideas as well, that we should look upon how there may be changes in the structure of iron complexes modeling, for instance the central part of hemoglobin and such things, changing the charges when you have reactions going on in different biological systems. We always had this biological point of view in the back of our considerations.

A: In looking back, how would you make sort of a résumé on all of your activities in Quantum Chemistry? Did you feel content by using these theoretical methods? Did you feel constricted by them while trying to depict the experimental facts?

F: No, I thought that one must try to formulate the problem in such a way that one can perhaps make one step forward! That was something that Klein was very eager to tell us. Do never expect that you can take big steps, you must always take small steps in order to achieve something. Oskar Klein was a fascinating personality, I mean even if he didn't work at just the kind of problems that we were involved in he gave us so many such wise advises that one should work in that way (58).

And one should always remember that one was never taking a step just by oneself. One was using what was behind and what the others had done; one should make a small step from where on one could perhaps continue. One should always look upon oneself as part of bigger system, not as an isolated thing. One should try to make a contribution that could be helpful also to others and never to be too eager to tell 'that was my idea', 'that is my idea'! What is important is, that science shall go forward.

A: So you were not at all aiming, like some do, at the Nobel prize?

F: No. No, no, no {laughing, I.'s n.}. I never thought of that. I realize that I was not of that category yet where there would be a Nobel prize. And that was also not so interesting. Interesting is, if you can take some small steps that would bring the thing forward.

A: This year, in Germany is the 'Goethe-Jahr'. Goethe said: "It's not the goal that counts but the way to the goal".

Well, with that I will conclude and I thank you very much, Professor Fischer-Hjalmars, for having given such an outspoken and vivid interview. Thank you very much.