Scientific Career
Hans established an impressive research line in Nijmegen that was both fundamentally oriented and strongly applied. On the fundamental side, he played a key role in experimental studies of molecular collisions and high-resolution spectroscopy, working on beam maser setups, interstellar OH masers, and crossed-beam experiments. In these, he used hexapoles to investigate molecular orientation and steric dynamics and was among the first to introduce UV lasers. This yielded crucial insights into elementary collision processes in astrophysical and atmospheric environments.
In parallel, he developed applied research inspired by societal challenges. Together with, among others, Peter Andresen, he initiated studies on combustion processes in flames, later expanding to emission reduction (NOx and soot) in engines. Using advanced laser diagnostics, his group measured molecular concentrations and soot particles directly in a single-cylinder engine and a heavy DAF truck diesel engine, in close collaboration with Eindhoven University of Technology. He also contributed to diamond growth research. His 2010 farewell lecture, titled “No Application Without Foundation,” succinctly captures his vision: fundamental research forms the basis for sustainable and innovative applications.
Mentor and Group Culture
Hans was an academic mentor in the fullest sense of the word. He supervised numerous PhD students and thesis students, who grew into independent researchers under his inspiring and careful guidance. Many now hold leading positions in science and technology worldwide. His Applied Molecular Physics group was known for its open atmosphere, close collaboration, and intensive discussions on experiments and results. Hans was demanding yet involved: he challenged to depth and precision while always attentive to personal development.
Commitment to Education
Education held as central a place in his career as research. Hans taught with clarity and enthusiasm, particularly in the early years of the physics program, and served as student career advisor. He was education director of Physics, later director of the Institute for Mathematics, Physics, and Astronomy (WiNSt), and vice-dean of education for the Faculty of Science, Mathematics, and Informatics. As the intellectual father of the broad Natural Sciences program (now Science), he integrated physics, chemistry, and biology in an innovative, multidisciplinary way. He advocated for applications and broadening to make programs excellent and student-friendly.
Personal Impression
Colleagues remember Hans as warm and collegial, a bridge-builder between fundamental and applied research and across disciplines. He connected people in national and international projects on combustion, diamond growth, and spectroscopy, yet remained modest: content and quality were always paramount. His family was a constant and vital factor in his life; he spoke gratefully of their support, even in difficult times, and kept the human perspective sharp.
We will miss Hans as a passionate researcher, dedicated teacher, and inspiring colleague. His legacy—in research lines, programs, and the careers of his students—remains tangible. Our thoughts are with his wife, children, grandchildren, to whom we extend our deepest condolences.
Bas van de Meerakker, Leo Meerts and Dave Parker
