Lorenzo Jan Curtis

Lorenzo J. (Larry) Curtis died on 29 March 2020 at his home in Toledo, Ohio.

Larry was a Fellow of the American Physical Society and also of the Optical Society. His APS Fellowship, awarded in 1985, was “For significant contributions to the field of atomic spectroscopy through a synthesis of precision experimental measurements, innovative computational analysis, and imaginative phenomenological modeling.”

Larry was born on 4 November 1935 in St. Johns, Michigan. He graduated from the University of Toledo with a BS degree in engineering physics and earned a PhD in physics from the University of Michigan in 1963 with research in elementary particle physics. Larry then joined the faculty of the University of Toledo, where he retired in 2006 with the rank of Distinguished University Professor Emeritus.

In 1970 Larry took a sabbatical leave to work at the Research Institute for Physics in Stockholm, which began a lifelong collaboration by which he was able to divide his time between the University of Toledo and the universities of Stockholm, Uppsala, and Lund in Sweden. On that first trip to Stockholm, Larry met his soulmate and future wife, Maj Rosander. During their years together, Larry held visiting scientist positions at the universities of Lyon, Berlin, Copenhagen, Oslo, and Princeton. In 1976 Larry was offered a faculty position at the University of Lund. By an agreement between Lund and Toledo, Larry then held joint positions at the two universities.

In Toledo, Larry collaborated with Richard M. Schectman in developing an accelerator laboratory for atomic physics research. In the early 1970s, they were one of the earliest groups in the country to make beam-foil measurements to study optical decay rates, which could be utilized to obtain elemental abundances in the Sun, stars, interstellar matter, and planets. Perhaps their best-known beam-foil work was a collaboration with Gordon Berry at the University of Chicago to study the production of atomic orientation and alignment in the beam-foil process. This produced a landmark paper (1974) showing that symmetry-breaking in the beam-foil excitation process by tilting the foil created oriented—spinning—excited helium atoms. The results led to many years of studies of quantum beats to measure atomic fine and hyperfine structures, by other groups throughout the world, as well as to a more detailed understanding of the atomic excitation processes as the fast ions exited from the final foil surface.

Larry applied his mathematical expertise to allow an order of magnitude enhancement of beam-foil lifetime measurements. It quickly became clear (by the late 1970s) that most beam-foil lifetime measurements appeared to give results systematically longer than theory. The problem was pinpointed to cascade repopulation and the resulting multi-exponential decays being observed. Standard fitting programs were shown to be the culprits because of the very nonlinear, non-unique nature of the multi-exponential fits. Larry developed a whole set of computer programs—ANDC, Arbitrarily Normalized Decay Curves—to couple the information of multiple decay curves from the same atomic ion. This became the standard procedure in most later beam-foil decay measurements and removed the previous discrepancies between experiment and theory.

Larry also played a major role in a unique experiment verifying the emission of an electronic transition in the negative lithium ion. This was the first transition ever observed from a negative atomic ion. The transition had been observed in lithium beam-foil spectra for several years without identification, until a theorist suggested it might be from a negative lithium ion. Larry’s experimental suggestion was simple: to apply an electric field along the direction of the excited ion beam so that speeds of the negative, positive, and neutral atoms would be different. A differential measurement reversing the electric field produced small changes in the decays of the charged ions and confirmed this unusual triply excited negative-ion state.
Systematic trends in the spectra of atoms and ions was a distinctive aspect of Larry’s work throughout his career. An example is his introduction of the singlet-triplet mixing-angle parameter, which allowed him to follow the effects of relativistic and multi-electron interactions as functions of atomic number and ionization state.

During his long career, Larry received continuous funding for his research from NSF, the US Department of Energy, the Swedish Research Council, and the Nordic Institute for Theoretical Atomic Physics. In 1999 he was awarded an honorary doctorate by the University of Lund. Altogether Larry’s research efforts resulted in well over 200 scholarly scientific papers, a respected graduate textbook on atomic structure, numerous coauthored monographs, and a tutorial contribution to the handbook on AMO physics edited by Gordon Drake. For many years Larry served as editor for atomic, molecular, and optical physics for Physica Scripta, and he contributed to the editorial board of Physical Review A as an adjudicator. Larry received many awards and honors at the University of Toledo, including Distinguished University Professor (1992) and Master Teacher in the College of Arts and Sciences (1993).

In March 2002 Maj was diagnosed with ovarian cancer and began a rigorous program of surgery and chemotherapy. Larry retired from active research, and for nearly five years they continued to have rewarding lives, traveling extensively, and relaxing on Maj’s family farm in the forests of Småland in Sweden. Maj passed away on 1 November 2006 in Toledo. Larry subsequently resumed his scientific research and wrote a number of articles proposing radical revisions to the teaching of elementary physics.