Werner Eissner

Werner Eissner passed away on 6 April 2022 at age 91.

Eissner was a pioneer in computational atomic physics and a founding member of two international collaborations, the Opacity Project (OP) and the Iron Project (IP) . Both collaborations aim to study the accurate features of atomic processes and obtain high-precision large-scale atomic data using the state-of-the-art R-matrix method with close coupling approximation and application of data for solving long-standing astrophysical problems. Together with Harry Nussbaumer, Eissner developed the well-known atomic structure program SUPERSTRUCTURE (SS). Later Eissner upgraded it with the relativistic Breit–Pauli approximation . SS has been incorporated into the AUTOSTRUCTURE atomic structure code.

Eissner spent a significant amount of his time at University College London (UCL), Daresbury Laboratory, and Queen’s University of Belfast, during which he, together with Michael Seaton and Philip Burke, laid the theoretical and computational foundation of the close coupling methodology and made crucial contributions of incorporating the relativistic effects in the Breit–Pauli approximation to the powerful R-matrix package of codes that are implemented by the OP and IP teams. Before that he was instrumental in the development of the IMPACT suite of close coupling codes at UCL.

Eissner’s contributions to science extend beyond his publications. He remained engaged in developing more powerful and robust programs. He dedicated his life for atomic physics. Although he was very charming and social, possessed remarkable knowledge of history, art, food, and was very active in hiking, swimming, and sport, he was also very shy and never had a family.

Eissner was born on 16 October 1930 to Bernhard Eissner and Frieda, née Eckert, in Goerlitz, Germany. His father left for the war on Germany’s side, and Werner never saw him again. He was raised by his mother. He went to a primary school during 1937–41 and to a secondary school during 1941–45 in Goerlitz, moved to Luedenscheid, and remained there during 1946–51. He was a very bright and witty student and liked to behave so with the kids he would met. He received a Vordiplom degree (similar to a BSc) by taking physics, mathematics, and chemistry at Goettingen University during 1951–53. He moved to the University of Tuebingen and received the rough equivalents of a MSc and PhD by taking physics, mathematics, and astronomy during 1954–66.

Eissner became involved in and found much pleasure in atomic physics when he moved to UCL in 1967 on a Culham stipend and later as an associate research fellow of the Royal Society to work with Seaton. He enjoyed working with Seaton and remained a collaborator of Seaton and the OP and IP team members for the rest of his life. He spent a year as a resident fellow at the Center for Theoretical Studies in Coral Gables at the University of Miami. Paul Dirac had just ended his three-year stay at the center before Eissner joined.

He returned to UCL in 1974 and remained there until 1980 as an SRC research fellow and as a senior lecturer. He co-supervised with Seaton many students. During 1980–85 he was the principal research associate at Daresbury Laboratory of the British Science and Engineering Research Council and collaborated with Philip Burke and his team. He moved to Queen’s University Belfast for carrying out research as the secretary of a British Collaborative Computational Project and worked on upgrading the R-matrix codes with relativistic effects during 1985–93. In 1992 he and Seaton were honored for lifetime achievements by an international symposium held at UCL.

He moved back to Germany in 1993 in a research position at the University of Bochum. He became an emeritus in 1995 but continued in the position until 1999. He held a similar position at Stuttgart University from 1999 until close to his death in 2022. He was a visiting scholar at many institutions, including Ohio State University and NASA Goddard. He revised and contributed to the atomic physics chapter of our textbook, Atomic Astrophysics and Spectroscopy. He had lifetime active collaborations, acted as co-supervisor of two Ohio State graduate students, with most of the OP and IP members.

His contributions to OP and IP and atomic physics will always be regarded with respect.

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