The photodynamics of the Ar-I2 complex and the formation of chemically bound argon
Final Report Abstract
Dissociation of superexcited states of I2 in He nanodroplets produces both cationic and anionic fragments similar to the free I2 molecule in the gas phase; the charged fragments are ejected out of the droplets either as pristine ions or as complexes with attached He atoms. The velocity of ejected product ions is massively reduced with respect to the gasphase. A sharp drop in the velocity with increasing number of He atoms attached to the ion is observed, similar to previous findings for neutral fragments. The speeds of anionic products are about half as high as those of the cations of the same mass. The cationic velocity distributions are strongly anisotropic despite the reduction of the absolute speeds by interaction with the He nanodroplet. This shows that the information about the direction of ejection of the fragment cation is largely retained. However, the observed positive anisotropy contrasts the negative anisotropy measured in the gasphase, implying that a different dissociation mechanism is at the origin of the detected ions. The pump-probe dynamics measured for the most prominent I+ and I- product ions shows now resemblance with the gasphase dynamics, but a strong dependence on the He droplet size. This indicates that the observed dynamics is entirely dominated by the interaction of the excited I2 and the I+ and I-ions with the He nanodroplet, similar to our previous observations for excited atoms attached to He nanodroplets. In future experiments using a pulsed nozzle suitable for corrosive gases, we will resume the originally proposed studies of the ArI2 complex. Furthermore, the detection of I+ and I- in coincidence, generated by laser-induced photoionization or by photoionization using vacuum ultraviolet radiation from a synchrotron, will reveal further details about the complex photodynamics of superexcited states of iodine and its complexes.
Publications
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Role of ion-pair states in the predissociation dynamics of Rydberg states of molecular iodine, Phys.Chem.Chem.Phys. 18, 18896 (2016)
J. von Vangerow, A. S. Bogomolov, N. V. Dozmorov, D. Schomas, F. Stienkemeier, A. V. Baklanov and M. Mudrich
