Last year Prof. Nimrod Moiseyev from the Technion-Israel institute of Technology turned 70 years old. This is an excellent opportunity for his many colleagues and students to celebrate his remarkable past, present, and future contributions to science. Nimrod’s work on unstable quantum states (quantum resonances) relates directly to fundamental processes such as auto-ionisation, vibrational pre-dissociation, gas-surface collisions, laser-induced atomic and molecular ionisation/dissociation, electron-atom/molecule scattering, and more. The complexity associated with these phenomena is due to the finite lifetime of intermediate states, which makes their accurate quantum mechanical description highly challenging. Nimrod’s main contribution was to model and inspect these phenomena beyond the realm of standard quantum chemical calculations, which are based on probability conservation at all times, owing to the Hermiticity of quantum mechanical operators. Nimrod developed and practiced successful approaches, which go beyond Hermiticity, allowing for loss of probability in particular regions in space. These approaches turn out to be natural for describing decay processes in atomic and molecular systems involving ionisation and dissociations. Not surprisingly, the fundamental approaches he developed for non-Hermitian quantum mechanics found relevance in many other fields. He recently revolutionised the study of systems with PT symmetry in optics, where he is currently very influential. In parallel, he is active in integrating his methods into standard ‘black box’ quantum chemistry codes. The output of Nimrod’s scientific work is summarised in more than 300 publications and reviews, as well as in his books on quantum mechanics and in particular his recent text-book ‘non-Hermitian quantum mechanics’ (Cambridge University Press, 2011), the first book ever written on this topic.
We are pleased to present this special issue of original research articles in the field of Quantum Dynamics and Resonances in Chemistry and Physics to honour Nimrod Moiseyev on his 70th birthday.