Prof. Neumark （Born March 27, 1955）and his research group carry out state-of-the-art experiments to probe fundamental problems in chemical physics. The projects in his laboratories encompass (i) reaction dynamics of bimolecular and unimolecular reactions, in which one maps out in detail the potential energy surfaces on which chemistry occurs, (ii) cluster spectroscopy and dynamics, which explore how the properties of matter evolve with size, and (iii) ultrafast x-ray science, where novel femtosecond and attosecond light source initiate and/or probe dynamics in the soft x-ray regime. Much of his work uses photoelectron spectroscopy of negative ions in either the frequency and time-domain to probe the spectroscopy and dynamics of transient and reactive species. His research has yielded new insights into transition state spectroscopy, the electronic and vibrational spectroscopy of clusters, the photodissociation of reactive free radicals, hydrated electron dynamics in clusters and liquid jets, and the ultrafast dynamics of helium nanodroplets excited by femtosecond soft x-ray pulses.