Author: Laura Hennemann

To become a “junior researcher” at the age of 66 years – Dirk Schwalm, a professor of physics at the University of Heidelberg for decades already, would not have had this idea without Daniel Zajfman, his friend and colleague for many years. In 2006, the two particle physicists – a German and an Israeli – talked about the future of their research group over a glass of red wine in an Italian restaurant in Heidelberg. “I am going to be the president of the Weizmann-Institute”, Zajfman said. It is a researcher’s dream job to be allowed to lead such an internationally renowned centre for basic research. Nevertheless, Zajfman was concerned about the mentoring of his doctoral students for which he would not have sufficient time. “Would you like to substitute me in my laboratory?”

A German physicist leading the laboratory of an Israeli colleague? In Rehovot? Until fairly recently such a trustful cooperation between scientists of two countries tainted by the Holocaust would have evoked outrage in many Israelis. However, after 50 years of political and scientific exchange, such cooperation is very much routine. This is an accomplishment not least due to special examples like the research friendship between Schwalm and Zajfman.

Taking a sip from his glass of wine Schwalm accepted the offer. Schwalm, who had just become the emeritus director of the Max-Planck Institute for Nuclear Physics in Heidelberg and honorary professor of the University of Heidelberg, had sufficient time to work in Israel. In addition, Zajfman would also step in if his doctoral students needed a mentor until Schwalm’s successor was appointed.

Enjoying research

Schwalm thus moved to the Weizmann Institute – not really as a “junior researcher”, but as a visiting professor. “Daniel loves to call me his oldest postdoc”, said Schwalm smilingly. “And he is right: This is exactly how I feel!” No committees, no reports, no official responsibilities. “Now I am again free to grapple with a physics problem a whole day long, to lay down my pen at night and to say: No, it still doesn’t work.” This is the researcher’s life that initially attracted him to physics. “And I feel great doing this.”

Daniel Zajfman felt the same when he left Israel 25 years ago to start as a junior researcher under Schwalm at Heidelberg. Zajfman, born in Belgium in 1959, emigrated to Israel when he was 20 years old. He studied physics at the Technion, the Technical University Israel in Haifa, and devoted his research to nuclear physics. This lead him to the USA, to the Argonne National Laboratory in Chicago. It was there where a Heidelberg one of Schwalm’s colleague gave a presentation on the Test Storage Ring (TSR), the experimental electron storage ring which had come into operation shortly before in Heidelberg. “This physicist mentioned all the projects they had planned for the TSR”, said Zajfman. This had a great deal to do with the research on highly charged atoms. “But charged molecules, which I would have preferred to research by means of this system, was not on his list.” When, after the presentation, Zajfman shared his ideas, it led to an invitation to the Max Planck Institute for Nuclear Physics in Heidelberg.

An Israeli in snow-covered Heidelberg

When he arrived in the freezing December of 1990, it snowed “like crazy”, Zajfman remembers. But Schwalm quickly warmed to Zajfman’s ideas, namely how the TSR could improve research on ionised molecules. The next summer, the two of them – Zajfman was by then a research group leader at the Weizmann Institute – already wrote a joint research proposal. They submitted the proposal to the German Israeli Foundation (GIF) and received funding for three years. “Our results were stunning from the outset” Zajfman said, and in 1993 the first joint scientific publication appeared: a research on the recombination of positively charged Hydrogen-Deuterium Molecules with one electron.

Since then, the friendship of Zajfman and Schwalm became a textbook example of German-Israeli cooperation. They have jointly published more than 90 scientific papers, they received GIF funding for a second term of three years, and, in addition, the German-Israeli Project Cooperation (DIP) financed their joint project from 1998 to 2002. This was one of the first projects to be funded by the DIP, which was only established in 1996.

During the course of their long-term cooperation, Schwalm and Zajfman, for example, researched the reaction of molecules in the laboratory that are present in interstellar space. Clouds of particles, mainly comprising hydrogen atoms and hydrogen molecules, are used here. How these molecules are formed, and the type of forces that again destroy them, was part of the iatrochemistry that fascinated both Schwalm and Zajfman. They studied the relevant molecules in a laboratory by means of a particle accelerator such as the Heidelberg Test Storage Ring.

How many times Zajfman had been to Heidelberg, the Israeli cannot recall. Schwalm also commutes regularly between Germany and Rehovot, not far from Tel Aviv. “When I agreed to join the Weizmann-Institute as a visiting professor, I promised Daniel that all his doctoral students would complete their studies.” That has long been done. Zajfman was appointed president for another five years, and Schwalm has been living in Israel and in Germany for the past nine years. With each visit he stays for two to three weeks, and then returns to Heidelberg for two to three weeks.

The slow story of their rapprochement

At first, the cooperation between Israeli and German researchers was not without friction. Schwalm, born in 1940, can remember well when a doctoral student from Israel joined his study group in Heidelberg in the late 1960s. The first attempts of both nations to get together again after the war and the Holocaust, were scarcely ten years ago. Scientific exchange was not common at all.

Only much later, did that Israeli student tell Schwalm that he had travelled to Heidelberg with much reservation, had examined his environment for possible signs of anti-Semitism, and was prepared to leave anytime. Fortunately, there were no negative incidents, and the young scientist stayed for the planned time. Schwalm related: “For us it was a very interesting visit, a doctoral candidate from a cultural environment which was rather foreign to us. ”When the war happened, I was still a child, which made it quite easy to me to engage in an ingenuous manner. Older colleagues did not always manage to do so.”

It was not that easy for everyone to open themselves to the other country. “Even in the 1990s there were some Israeli researchers who refused to accept money from Germany”, said Schwalm who chaired the Grant Committee of the Minerva Foundation for German-Israeli research projects from 1994. “It was against their principles to submit proposals to Minerva”.

Today Schwalm no longer notices any Israeli reservation towards Germans. “I am proud that I could contribute to this”.