JOHANNA M. H. LEVELT SENGERS (1929-2024)

BY HRATCH G. SEMERJIAN

JOHANNA MARIA HENRICA LEVELT SENGERS — known as Anneke to her family, friends, and colleagues — was born in Amsterdam, the Netherlands, on March 4, 1929. With her father, Willem Levelt, having a Ph.D. in chemistry, and her mother, Josephina Berger, possessing a master’s degree in physics, education and science were central to their family culture. However, as the oldest of 10 children, some family members and friends expected her to stay home after finishing high school to care for her younger siblings. But Anneke had more ambitious plans! After applying for and receiving an interest-free government loan, she enrolled at the University of Amsterdam, home of Nobel Laureates Johannes Diderik van der Waals (NAS) and Pieter Zeeman. Her parents supported her choice.

She earned her Candidaats (B.Sc.) degree in physics and chemistry in 1950 and her Doctoraal (M.Sc. equivalent) in physics in 1954 from the University of Amsterdam. For her doctoral dissertation, she worked under the guidance of Antonius Michels in the Van der Waals Laboratorium on the “Compressibility of Argon in the Gaseous and Liquid Phase.” After receiving, in 1958, her Ph.D. degree in physics from the University of Amsterdam, she spent a year at the University of Wisconsin’s Institute of Theoretical Chemistry, as a postdoctoral research associate. From 1958 to 1959, she worked with renowned Joseph Hirschfelder (NAS). Returning thereafter to the Netherlands, she worked as a research physicist at the Van der Waals Laboratorium from 1959 to 1963. She also served as a lecturer for an academic year at the University of Nijmegen from 1962 to 1963.

She met her future husband, Jan V. Sengers, in the early 1950s while they were both in graduate school. Jan received his Ph.D. in physics in 1962, and the couple became engaged soon thereafter. Jan recalled, “At the time, it was difficult for married women to pursue a scholarly career in the Netherlands.” While doing their doctoral research, they connected with National Bureau of Standards (now the National Institute of Standards and Technology–NIST) researchers and explored the possibility of moving to the United States for academic opportunities. After receiving a positive response, they married in 1963, emigrated to the United States later that year, and joined the NBS.

Anneke worked with her collaborators on critical phenomena in fluids, fluid mixtures, and ionic fluids, covering everything from theory to experiment and databases for practical applications. They developed critical region scaling concepts for fluids and fluid mixtures and investigated solubility behavior near a solvent’s critical point. Their research included measuring density, phase behavior, and other properties of industrially significant fluids such as carbon dioxide, ethylene, water, and geothermal fluids. They also contributed to databases on the properties of water and steam for applications in science and the electric power industry, focusing on critical properties, refractive index, and dielectric constant correlations at high pressures and temperatures. Several of these databases have become standards of the International Association for the Properties of Water and Steam (IAPWS), and some were embedded in the American Society of Mechanical Engineers (ASME) Steam Tables. As an NBS group leader (1978-87), she oversaw projects on alternative refrigerants, ionic fluids criticality, and supercritical fluids and their mixtures. In 1984, she was elected a NIST Senior Fellow, the highest technical rank conferred by the institute. She served in this capacity until her retirement in 1995.

During her 32-year career at NIST, she not only initiated and contributed to numerous scientific research programs and international collaborations but also organized many scientific meetings and symposia. She had a particular interest in applying fundamental knowledge to energy conversion and chemical process technologies. Besides publishing more than 150 articles in archival journals and conference proceedings, she also contributed 14 book chapters and authored four books.

Her outstanding research attracted collaborators from around the world. Anneke once said: “My work was enriched by many postdoctoral researchers from the U.S. Because of my early international engagement, I was also able to attract postdoctoral researchers from several European countries, the former Soviet Union, Japan, and Argentina. I was particularly proud of the gifted postdoctoral women to whom I could give a boost at a time when hurdles were high for women aspiring (to) careers in science and engineering.”¹

Her remarkable accomplishments were recognized with numerous awards, including the U.S. Department of Commerce Silver Medal Award (1972); the NBS Edward Uhler Condon Award for her early research on critical phenomena (1975); and, in 1978, the U.S. Department of Commerce Gold Medal for Distinguished Service Award. In 1985, she received the WISE Award—Federal Woman in Science and Engineering. She was honored with the prestigious Alexander von Humboldt Research Award in 1991 and served as a visiting scientist at the Ruhr-Universität Bochum in Germany. In 1992, she was elected to the National Academy of Engineering, receiving the highest professional recognition “for elucidation of the critical behavior and thermophysical properties of industrially important fluids and fluid mixtures.” That same year, she was elected a fellow of the American Physical Society, and in 1990, a Correspondent of the Royal Netherlands Academy of Arts and Sciences. In 1992, Anneke and her husband, Jan, were awarded honorary doctorates from Delft University of Technology (TUDelft), in celebration of the university’s 150th anniversary. Not only was Anneke the first woman to receive an honorary doctorate from TUDelft, but also she and Jan became the first couple to receive joint honorary degrees at any university in the Netherlands. The award ceremony was presided over by Queen Beatrix of the Netherlands. Throughout her career, she was in high demand as a lecturer and visiting researcher in the international scientific community. She served as a visiting lecturer at the University of Louvain in Belgium (1971); a research scientist at the Institute for Theoretical Physics in Amsterdam (1974-75); and a Regents’ Professor in the Chemistry Department at the University of California, Los Angeles (1982). Anneke was an active member of the ASME Research Subcommittee on the Properties of Water and Steam, which maintained and upgraded the ASME International Steam Tables. This subcommittee also served as the U.S. National Committee to the International Association for the Properties of Water and Steam (IAPWS), where she held multiple leadership roles. From 1990 to 2004, she was the U.S. national representative to the IAPWS and also served as IAPWS president.

Anneke was not only a world-renowned scientist and researcher, but also a loving mother who doted on her children, never losing sight of the importance of her family. It was always obvious to those who knew her that her husband and her children were the most important people in her life. Anneke and Jan had four children who are all accomplished in their own right: Rachel is a web designer; Arjan has a Ph.D. in electrical engineering; Maarten is an attorney; and Phoebe is a professor of information science at Cornell University.

In 1996, shortly after she retired from NIST, Anneke was elected to the National Academy of Sciences (NAS). Being elected to both NAE and NAS is not uncommon, but she was among the very few women to receive both honors. She was an active member of the Academies, serving on the NAE Peer Committee (Chemical Engineering) (1998-2001); as the NRC Liaison (1998-2001); on the NAE Committee on Membership (Chemical Engineering) (2004-06); and on the NAE Founders and Bueche Awards Selection Committee (2011, 2012).On the occasion of Anneke’s retirement, her colleagues Jakob de Swaan Arons and Cor J. Peters from Delft, wrote a guest editorial in The Journal of Supercritical Fluids to honor her contributions: 

“Dr. Johanna M. H. Levelt Sengers has recently retired from her official position at the National Institute of Standards and Technology (NIST) where she had been a Senior Fellow since 1984. It is with great pleasure that we take this occasion to highlight her distinguished career and the many significant contributions she has made to the world of science…To many of her colleagues she is known by the friendly name Anneke. In 1985, the Americans had proclaimed her to be the ‘most outstanding woman in federal science and engineering’ and the Russians called her - with good reasons - the ‘most thermodynamic woman in the world.’ Indeed, Anneke excels in the field of thermodynamics, a discipline that Albert Einstein once characterized as universal and timeless…Her publications on critical phenomena, thermophysical properties and phase behavior of fluids, some of which were co-authored by her husband, Jan Sengers, an equally distinguished scientist at the University of Maryland, are considered classic in the field…Although Anneke is now formally retired, we know that she will never turn her back on science. …After many years of intense activity, we are pleased that she will continue to have further enjoyment in pursuing knowledge in her favorite areas and continue to interact with the scientific community.”²

This praise was well placed — because even 20 years after her retirement, there did not seem to be any indication of Anneke slowing down. She returned to her whirlwind schedule as a visiting lecturer at the University of Utrecht (1999), presented colloquia at various universities, and reviewed books. She also found time to research one of her favorite topics, the history of the Dutch School of Thermodynamics, and published How Fluids Unmix,³ which explored the discoveries of the Van der Waals and Kamerlingh Onnes school of thought.⁴ Recognitions of her scientific accomplishments continued. She was elected a member of the Royal Holland Society for Sciences (2002) and honored as a fellow of the American Association for the Advancement of Science (2003). In the following years, she was elected a fellow of the ASME (2005) and received the Yeram S. Touloukian Award from ASME (2006).

In 2003, UNESCO, along with L’Oréal, the cosmetics company, named her the North American recipient of the Women in Science Award. The award recognized her long career at NIST, where “she had made internationally recognized contributions, both theoretical and experimental, to the fields of thermodynamics and critical phenomena of fluids (fluid behavior near or at the point when a vapor becomes indistinguishable from a liquid).” The selection committee was headed by Pierre-Gilles de Gennes, the 1991 Nobel Laureate in Physics.

Having been born and educated in Amsterdam, Anneke reflected on her experience as an immigrant scientist, writing: “As an immigrant to the United States, I have found at NBS a work environment where I felt welcome and accepted, where even in the 1960s women scientists had successful careers, where special arrangements were made for me while I was raising my family, and where I was given all support to succeed.” Before leaving the Netherlands, Anneke was already pregnant with their first child—but that did not seem to have slowed her down, since she published her first paper on NBS research within two years of her arrival in the United States.

However, she was keenly aware that not all women found such a welcoming environment. Throughout her career, she advocated for greater gender equity in science and engineering. For the 20th Annual Shih-I Pai Lecture titled “Pride and Prejudice in Science and Engineering,” she wrote:

“During my career I have worked with scientists, engineers, and postdoctoral collaborators, both men and women, from the U.S. and from many foreign countries. In the past 10 years, within the context of the Network of the Academies of Sciences, I have chaired first a global, then a Western Hemisphere initiative addressing the low representation of women in science and technology. Sociologists have produced solid evidence of gender prejudice even within the physical sciences that take pride in their objectivity. The (Inter-American Network of Academies of Sciences) IANAS book: Women Scientists in the Americas. Their Inspiring Stories strikingly illustrates culture-dependent gender prejudice that keeps the physical sciences and engineering preponderantly male occupations in countries such as the U.S., U.K., and Germany. The near absence of women from engineering, as well as ignorance about local culture and gender roles, adversely affect development work by foreign engineers serving the poor in the third world. Indeed, both women engineers and social scientists have unique roles to play in overcoming cultural prejudices which waste women’s talents and hamper development work.”⁵

Due to these concerns, she served as the co-chair of a panel on the InterAcademy Council and co-authored a report entitled Women for Science, written to advise global science and engineering academies on how to attract, retain, and promote more women in science and technology fields.⁶ An article in Science highlighted the report’s findings and underscored her commitment: “Sengers stands at the top of her profession but confesses that ‘it can be a little lonely’ as one of only two women in the 82-member engineering science section of the National Academy of Sciences… The report…offers a refreshingly candid assessment of the problems facing women trying to enter and move up in the world of science and engineering…it sings a new tune in commanding the National Academies themselves to ‘first put their own houses in order.’”⁷ To advance these recommendations, Anneke organized and chaired the First Focal Points Meeting of the IANAS Women for Science working group in Mexico City in 2011, as well as meetings in Panama (2012), and Chile (2013).

Anneke was an inspiration to the men and women of NIST and the global scientific community. Her dedication to science, boundless energy and enthusiasm, deep concern for her fellow scientists and engineers, and, above all, her love of family left a lasting impact. She died on Feb. 28, 2024, leaving a big gap in the scientific community. She is survived by her husband Jan, four children (Rachel, Arjan, Maarten, and Phoebe), and five grandchildren.

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¹ Personal communication, email. March 2016.
² Arons J de S, Peters CJ. 1996. Guest editorial. The Journal of Supercritical Fluids 9(1):iii-iv.
³ Levelt Sengers J. 2002. How Fluids Unmix – Discoveries by the School of Van der Waals and Kamerlingh Onnes. Amsterdam: Royal Netherlands Academy of Arts and Sciences. Available at https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831808. 
⁴ Levelt Sengers J. 2009. A gas that sinks in a liquid – the first helium experiment published by Kamerlingh Onnes. Journal of Physics: Condensed Matter 21(16):110.
⁵ Institute for Physical Science and Technology and the Department of Physics. 2014. Pride and prejudice in science and engineering. 20th Annual Shih-I Pai Lecture. University of Maryland. Oct 7. Available at http://ipst.umd.edu/flyers/pai2014brochure.pdf. 
⁶ InterAcademy Council. 2006. Women for Science: An Advisory Report. Available at https://www.interacademies.org/publication/women-science. 
⁷ Mervis J. 2006. Report urges National Academies to improve status of women. Science 312(5782):1859.