We have just learned the very sad news of the passing of our friend and colleague Roland Lefebvre. He passed away in Goussainville, on Sunday, June 20, 2021, at the age of 93.

Son of the sociologist Henri Lefebvre, born on January 20, 1928 in Paris, Roland Lefebvre was the widower of our late colleague Hélène Lefebvre-Brion who passed three years earlier. Both had pursued their brilliant research careers at the CNRS Laboratory of Molecular Photophysics, of which Roland was one of the founders with Sydney Leach, François Legay and Lars Lindqvist, as well as its director from 1982 to 1988. Roland continued his research activities until recently as Emeritus Professor (since 1996) at the University Pierre et Marie Curie (Paris Sorbonne) and at the Institute of Molecular Sciences of Orsay (ISMO).

In a life entirely dedicated to research, with an unlimited commitment and motivation, a capacity for abstraction, rigor, and perpetual questioning, Professor Roland Lefebvre’s work has focused on the theoretical aspects of Molecular Physics, from electronic correlation and hyperfine structures, paramagnetic resonance, superradiance and photon echoes, quantum collision theory and radiation-matter interaction, to problems of control by intense electromagnetic fields of time and energy-resolved electron-nuclear dynamics. This work has always been marked by great originality, going far beyond simple numerical simulation. For him, it was essential to bring a high level of understanding and conceptualization to his research, such as the discovery of basic mechanisms with a strong level of transposability to various systems, or the application of unexpected properties of a range of exotic resonances - those with zero width (an oxymoron, as he liked to say) - or of so-called exceptional points, of which he was the instigator at the end of his career.

Member of the International Academy of Quantum Molecular Sciences (IAQMS), Roland Lefebvre was recipient of the Pascal Prize of the Academy of Sciences. His large scientific production includes a book co-authored with R. Daudel and C. Moser, and an editorial activity concerning five collective works, a set of about 230 articles published throughout his long and very fruitful scientific life, from 1953 (year of his PhD thesis defense at King’s College in London), until recently in 2020 (year when he had to stop his work due to the Covid pandemic).

Roland Lefebvre had built a large network of international collaborations (Israel, Mexico, Canada, USA, Germany, UK, Greece, Australia, Japan). He enjoyed much opportunities for teamwork, where with all his rigor and all his competency, he shared his knowledge and his inexhaustible enthusiasm for Physics. He commanded and fostered our admiration and respect until the very end of his life, as much for the strength of his reasoning, as for his scientific culture and the precision of his mathematical thinking. He was also a reserved person, but of absolute honesty and whose passion thrived around scientific exchanges.

It is with deep sadness and sorrow that we experience the loss of this Colleague and especially a dear Friend.

Osman Atabek and Thomas Pino