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In our last study [J. Phys. B At. Mol. Opt. Phys. 54, 125,102 (2021).], we reported the ab initio calculation of the full-dimensional potential energy surfaces of water molecule including 9 A’ and 9 A” states in Cs symmetry. In this study, we performed additional non-adiabatic semi-classical studies based on the potential energy surfaces. Our simulation successfully repeated the near picosecond lifetime of the F∼1A′ state measured by time resolved photo-electron spectra experiment [Chinese J. Chem. Phys. 32, 53 (2019)]. We also determined the dissociation branching ratio including H + OH(X, A), H + H + O and H2+O channels. In addition, the reaction path corresponding to H2+O (1S) channel is clearly marked out, which is found in recent free-electron laser experiment [Nat. Commun. 12, 6,303 (2021)].

We present ab initio calculations of cross sections for projectile and target excitation occurring in the course of He+ + He collisions using a three-active-electron semiclassical nonperturbative approach. Intermediate impact energies ranging from 1 keV to 225 keV/u are considered. The results of our calculations agree well with available measurements for both projectile and target excitation in the respective overlapping energy regions. A comparison of our results with those of other theoretical calculations further demonstrates the importance of a nonperturbative approach that includes a sufficient number of channels. Furthermore, it is found that the cross sections for target excitation into singlet states show a valley centered at about 25 keV/u, resulting from competition with electron transfer to singlet projectile states. By contrast, the cross sections for target excitation into triplet states do not exhibit any such structures.

Interatomic or intermolecular Coulombic decay is responsible for the generation of slow electrons in clusters and biological samples. Here the authors use electron–electron coincidence detection to find the competitive roles of proton transfer and ICD that occur on similar time scales in water clusters.