Paul-Henri Heenen, Professor emeritus of the Université Libre de Bruxelles and a renowned nuclear physicist, passed away on 1 June 2019 at the age of 71. Born in Brussels, he received his master's degree at the Université Libre de Bruxelles in 1970. He continued his Ph.D. studies under the supervision of Professor Marcel Demeur, on a quantum description of low-energy nuclear reactions, and obtained his degree in 1975.
After his Ph.D. thesis, Paul-Henri stayed at the IPN-Orsay, University Paris-Sud, where he reoriented his research activities toward mean-field methods and spectroscopy of heavy nuclei. This was the beginning of a long-standing collaboration with Hubert Flocard and Paul Bonche. Together, they developed new and original schemes for solving self-consistent mean-field equations in a precise 3D coordinate-space representation, a numerical challenge that required the use of the most powerful computers of the time. Their study of isotopes with very different shapes according to their number of neutrons, remains a reference publication in nuclear spectroscopy. In the 1980s, Paul-Henri broadened his international collaborations during several stays in the United States, including Berkeley and Livermore. These developments were the subject of his habilitation thesis, completed in 1985.
Their numerical tools were then extended to the study of super-deformed nuclear states at low and high spin. In the 1990s, the experimental confirmation of such states was a major advance in the study of nuclear structure and its limits. In parallel, Paul-Henri and collaborators pioneered the application of the exact Generator Coordinate Method to the description of shape fluctuations and shape coexistence, later on in combination with symmetry restoration. Paul-Henri's activity has always been in close collaboration with experimental groups in Europe and the United States. A review article on self-consistent mean-field models, published in 2003 in Reviews of Modern Physics, presents the different aspects of these methods applied to the structure of nuclei and remains an essential reference in this field.
At the turn of the century, Paul-Henri joined the Belgian program on radioactive beam research, a collaboration between the universities of Brussels, Gent, Leuven, and Louvain-la-Neuve. Paul-Henri's contribution was not limited to interpreting data stemming from this activity but included his essential theoretical guidance to continuously shape a science program that ran over three decades.
Paul-Henri was a researcher at the Fonds National de la Recherche Scientifique in Belgium until 1998. In 1999, he was appointed full professor at the Université Libre de Bruxelles (ULB). He was strongly involved with lectures, and was very active in the administration of the Physics department and of the computer center at the ULB. He received several awards in Belgium and was member of the Royal Academy of Belgium since 1999. For his achievements in nuclear-structure calculations, he was elected fellow of the American Physical Society.
Paul-Henri was always eager to compare experimental data and theory, and also to share his knowledge with students. He conducted his research in numerous collaborations in Europe, in the United States, and in Japan and contributed to a rigorous and systematic approach to the study of nuclear structure in different states at the limits of stability. Over the decades, he has educated with great passion many young scientists who are now carrying on his legacy.
Paul-Henri was a member of several committees in Belgium and abroad. He served in the Programme Advisory Committee of several laboratories. He was an active member of NuPECC, and board member of the ECT* in Trento. More recently, he joined the ENSAR2 Committee, which coordinates the activities of European nuclear physics in the medium and long term. He also served on the editorial committee of Physicalm Review Letters and of Report on Progress in Physics.
Paul-Henri Heenen's research was unanimously recognized as innovative and varied. It has influenced, directly or indirectly, a large number of Belgian and foreign researchers. An Honorary Professor since 2013, he actively pursued his research activities. The scientific community loses an excellent researcher and teacher, but also a person of great human quality, unanimously appreciated. He leaves behind his wife, two daughters, and four grandchildren.