Their names are in the history of science

In memory of a colleague from Germany

A year ago, on 18 October, 2022, Professor Friedrich Gonnenwein passed away at the age of 88. He was well known in FLNP and FLNR of JINR, he repeatedly visited Dubna and participated in conferences. His German colleagues published an obituary in the Physik Journal. The Dubna scientists, on whose initiative this matter was prepared, also retained warm memories of Friedrich.

After graduating from high school in Homburg, Friedrich entered the Stuttgart Music College to study piano and organ, later, he completed an internship in organ making in a workshop in Hamburg. These years developed many qualities in him that he later passed on to his students. In the winter semester, in 1953-1954, Friedrich finally began to study physics at the University of Tubingen and in 1959, he defended his thesis. This was his first encounter with nuclear fission, a field of physics that he remained faithful to for the rest of his life. In 1964, he defended his doctoral thesis "Fission of uranium-238 using 14 MeV neutrons" at the Physics Institute of the University of Tubingen, in 1974, he became an associate professor, dean of the faculty of physics and finally in 1978 - professor of nuclear physics. Which student did not know his books on experimental physics in the 1980s?

From 1979 to 1985, F.Gonnenwein worked as a senior researcher at the Institute Laue-Langevin (ILL), France and afterwards, he headed the technical services of EDEX for some time. He participated in the operation of the ILL high-flux neutron reactor and in the development of a high-resolution slit spectrometer that became an integral part of ILL instruments. Upon his return to Germany in 1985, the University of Tubingen awarded him the title of full professor - a rare honor!

In 1986, after the Chernobyl accident, Friedrich, along with other nuclear physicists, shared with the public their knowledge of radioactivity, nuclear fission and nuclear reactors and measured background radiation in playgrounds and other public places. Collaborating with physicists from socialist countries and participating in joint experiments in the field of nuclear physics, he earned an outstanding reputation in international institutes. In 1988, Friedrich officially retired, but almost every day, he visited the institute at thematic seminars and colloquiums with fundamental discussions, his papers were published and he was invited to give lectures around the world. His paper was published in a peer-reviewed journal in 2021. Friedrich Gonnenwein was not just a talented university teacher and an extremely successful researcher, he was a man that thought about the future of the planet. We have all lost a respected colleague, staff member and friend.

In 2003, the G.N.Flerov Prize was awarded to J.Hamilton (Vanderbilt University), F.Gonnenwein (University of Tubingen) and JINR staff members M.G.Itkis and G.Ter-Akopyan for research on spontaneous nuclear fission and nuclear fission, induced by neutrons and charged particles.

"Friedrich is one of the most famous specialists in the field of fission," Professor M.G.Itkis (FLNR) recalls his colleague. "I have known him since time immemorial. Our laboratory has collaborated with him for many years. His main work was related to the investigation of parity violations not only in weak, but also in strong interactions. He carried out experiments for many years at the Laue-Langevin Institute in Grenoble. Friedrich is co-author of a monograph on the physics of neutron-induced fission. He came to Dubna more than once, met with young people in our laboratory, taught them wisdom."

"I met Friedrich Gonnenwein in 1993-1994, when I was on an internship at the Technical University of Darmstadt," FLNP Deputy Director Yu.N.Kopach said. "Then an agreement was reached on the exchange of students between JINR and Germany. So, I went to Darmstadt for a year and got involved in a very interesting experiment that was carried out in Heidelberg with the participation of several centres in Germany, including the Technical University of Darmstadt. Friedrich Gonnenwein was the head of the team from the University of Tubingen. The experiment was successful and I went about Friedrich for several years while preparing the publications. From 1999 to 2002, I worked at GSI in Darmstadt and later, we got to know each other better. I was involved in division and Gonnenwein was a man that knew almost everything about division and had been involved in division all his life. Not only was he well versed in theory, but he was also a good experimenter, although in recent years, he had been more involved in organizing experiments. He had a large library, he followed the literature very closely and knew all the new papers on the subject of division. He himself wrote a book based on lectures he gave in Grenoble, Strasbourg and other places where he was specially invited.

F.Gonnenwein, Yu.N.Kopach and I.Ruskov. ISINN-27, Dubna, 2019

One of the main activities of his life, at least in the last years, when I talked to him, was the investigation of the so-called T-odd effects in fission. I was not involved in this research from the very beginning. They started back in the late 1990s in Grenoble with a mixed team: from Russia the group of G.V.Danilyan (ITEP) and the group of G.A.Petrov (PNPI) participated and from Germany - the groups of F.Gonnenwein (Tubingen) and M.Muterer (Darmstadt). After some time, a group from FLNP also joined these experiments. Initially, these experiments were aimed at searching for violations of temporal invariance in fission. The effects of T-noninvariance have been pursued for a long time; FLNP once had such a research programme; at ISINN it was one of the most important topics. And the first ISINN, when the conference had not yet acquired its name, was held as a workshop to search for the effects of violation of spatial parity and time invariance. So, no one was able to measure the effect with sufficient accuracy, but they immediately obtained a huge effect, comparable to that observed in P-odd correlations. For some time, this effect could not be explained. Some models were proposed, but they were not very convincing; there was no clear evidence that such an explanation works. Gonnenwein even said that if no one came up with an explanation within a year, he would consider that they had discovered the T-violation effect. In the end, an explanation was found that showed there was no violation of time invariance, although the effect turned out to be very important for understanding the fission process. Nevertheless, the effect continued to be called the TRI effect (Time Reversal Invariance, the effect of violating invariance with respect to time reversal).

Later, the same team discovered another effect, in which, during fission, a certain angle of rotation in the escape of the particle was observed, so it was called the ROT effect (from the English rotation). Both names were coined by Gonnenwein. As it turns out, these two effects are of a similar nature. A large article was published describing both the effects themselves and the models that explain them. Friedrich made a decisive contribution to its writing and to the development of a theoretical model describing these effects. Although, not all theorists agreed with the interpretation presented by the experimenters. We can say that this discovery gave a great impetus to the development of the theory. It is carried out at Voronezh University in the department that was previously headed by S.G.Kadmensky, A.L.Barabanov from the Kurchatov Institute, V.E.Bunakov (St. Petersburg). The number of published papers describing these effects amounts to many dozens.

We met Friedrich in another experiment that was carried out in Strasbourg at the DEMON facility, consisting of large scintillation neutron detectors. The idea of the experiment was put forward by Gonnenwein and it was to measure the angular correlations not between neutrons and fission fragments, as is usually done, but between two neutrons and a fission fragment that could provide information about how much the spins of fission fragments influence the angular distribution of neutrons. The experiment was carried out and such a correlation was indeed discovered, albeit at the limit of sensitivity.

F.Gonnenwein visited Dubna quite often, he had good relations with the group engaged in fission at FLNR. He participated in our ISINN conferences. At one of them, in 2004, an excursion to several cities of the Golden Ring was organized. My wife and I talked to him a lot during this trip and realized that he is a very versatile person. He really enjoyed this trip and later remembered about it several times. It was easy to communicate with him, from the very beginning we talked to each other in an unofficial form, despite the big age difference. He had many students, I found him an active professor and the atmosphere of communication in their group was very cordial. I especially felt it at the wedding of one of the graduate students, to which Friedrich, his entire group and me were invited. He continued to keep in touch with his former students and they kept in touch with him and got together periodically. I remember, during experiments, when there were no small parts or the required tools, he himself went to the store and bought what he needed with his own money. For him, the main thing was the experiment to be carried out.

Friedrich was closely related to music; he not only loved it, but also understood it well as a physicist, in particular. In 1995, JINR held a school on neutron physics in Ratmino, in which Friedrich participated as a lecturer. In addition to his main report, he gave a lecture on the topic: music and physics. He told us how the ear works, why some sounds are pleasant to us and some are not, what harmony is. It was very interesting. I remember that when there were concerts in Dubna during ISINN, he always went to them and then shared his impressions."

Olga TARANTINA,
photo by Elena PUZYNINA