Examining Electronic Excitations in Liquid Water under Proton and Photon Irradiation*

Proton and Photon irradiation of liquid water is important in many areas of modern technology, including cancer beam therapies. However, understanding the molecular level details of induced electronic excitation has been elusive. Using real-time time-dependent density functional theory, we study the dynamics of electron excitation in liquid water through the propagation of maximally-localized Wannier functions (MLWFs). The MLWF dynamics provide a convenient “molecular orbital” picture of the electronic structure, to understand electronic excitation in terms of localized electrons. We examine the extent to which photo-excitation and electronic stopping excitation differ at the molecular level.