In Memoriam: Marilyn Jacox

Marilyn E. Jacox, an internationally recognized leader in molecular spectroscopy who joined the National Bureau of Standards (NBS) in 1962 and spent the remainder of her career here, died on Oct. 30, 2013 at the age of 84. Her decades of distinguished research – much of it conducted in an era that was not always welcoming to women in science – culminated in comprehensive spectral databases that are standard references today, as well as a variety of seminal, widely cited publications.

"Marilyn was a scientific hero to many of us," said Gerald Fraser, Chief of NIST's Sensor Science Division where Jacox worked, "both for her important and lasting contributions, and as an ardent supporter of women and young people in science. She will be deeply missed by us all."

Katharine Gebbie, former Director of PML and its precursor, the Physics Laboratory, said that "Marilyn is an icon both for her scientific stature and her warm friendship. NIST will never be quite the same without her."

Jacox, a physical chemist and NIST Scientist Emeritus at the time of her death, specialized in infrared spectroscopy of free radicals, small molecular ions, and other reaction intermediates, typically embedded in a surrounding matrix of inert species such as nitrogen or noble gases at cryogenic temperatures.

Those "matrix isolation" measurements reveal otherwise hidden properties of free radicals, which are the carriers of many chemical reactions. "The infrared spectrum of a molecule tells us how its atoms vibrate with respect to one another and is as characteristic of the molecule as a fingerprint is of a person. Analysis of this spectrum provides sometimes surprising information about the structure and chemical bonding of the molecule in its lowest-energy electronic state," she wrote in 2010 describing her work. "The electronic spectrum provides information on the molecule in more highly excited electronic states." Thousands of observations make up her compilation of Vibrational and Electronic Energy Levels of Polyatomic Transient Molecules (1990), which she subsequently revised and supplemented many times, and which remains part of NIST's Standard Reference Data.

Marilyn Jacox had become interested in physical chemistry in high school, and pursued it as an undergraduate at Utica College of Syracuse University, during her doctoral research at Cornell University and postdoctoral experience at the University of North Carolina, and in her appointment in 1958 as a Fellow of the Mellon Institute of Industrial Research in Pittsburgh. In 1962, she joined the Surface Chemistry Section of NBS, where she and longtime collaborator Dolphus Milligan made pioneering spectral measurements that spanned decades and laid the foundation for the database.

"No one in the matrix isolation community will disagree that she is the most important contributor after George Pimentel initiated the matrix isolation technique in 1954. She conducted numerous ground-breaking studies, and her careful work was seldom questioned," said Yuan-Pern Lee, a leading expert in chemical dynamics and spectroscopy at Taiwan's Institute of Atomic and Molecular Sciences, Academia Sinica. "She also wrote many reviews and book chapters to summarize important advances in this field. When the George Pimentel Prize for Advances in Matrix Isolation was initiated in 2005, naturally she was the first to receive it."

Her many other awards include the U.S. Department of Commerce Gold Medal for Distinguished Service, the E. Bright Wilson Award in Spectroscopy from the American Chemical Society, the Federal Woman's Award, the NBS Samuel Wesley Stratton Award, and the Washington Academy of Sciences Award for Distinguished Career in Science. She was a Fellow of the American Physical Society and the American Association for the Advancement of Science, was elected President of the NIST chapter of Sigma Xi, served on the editorial boards of two major journals, and in 2000 was honored by a festschrift in the Journal of Physical Chemistry. Her picture hangs in the NIST Portrait Gallery.

Another eminent figure in matrix-isolation spectroscopy research, Lester Andrews, Professor Emeritus of Chemistry at the University of Virginia, was a friend and colleague of Jacox for many years. "As a scientist, Marilyn was fiercely competitive as we all must be, but she was objective and honest in all of her dealings," he said. "The greatest compliment that I can pay her is to wish that she could have refereed all of my submitted manuscripts. Thus, I would have gained more improvements for my papers than I could have from any other person."

Molecular physicist William R. M. Graham, Chair of the Department of Physics and Astronomy at Texas Christian University, said that Jacox's "exacting standards in her research and its publication set a very high bar for her colleagues in the field." In addition, "with her warm personality she generously shared results and advice with her colleagues, particularly young people setting out on their careers. She was a strong advocate for women in science, and her career provided an inspiring example."