A complete quantum mechanical study of chlorine photodissociation

Doubly charged dimers and trimers of heavy noble gases

Many doubly charged heteronuclear dimers are metastable or even thermodynamically stable with respect to charge separation. Homonuclear dicationic dimers, however, are more difficult to form. He22+ was the first noble gas dimer predicted to be metastable and, decades later, observed. Ne22+ is the only other dicationic noble gas dimer that has been detected so far. Here, we present a novel approach to form fragile dicationic species, by post-ionization of singly charged ions that are embedded in helium nanodroplets (HNDs). Bare ions are then extracted by colliding the HNDs with helium gas. We detect homonuclear doubly charged dimers and trimers of krypton and xenon, but not argon. Our multi-reference ab initio calculations confirm the stability of Kr22+, Kr32+, Xe22+, Xe32+, and Ar22+, but put the stability of Ar32+ towards dissociation to Ar+ + Ar2+ into question.

The vibrationally mediated photodissociation of Cl2

The photodissociation of vibrationally excited Cl(2)(v = 1) has been investigated experimentally using the velocity mapped ion imaging technique. The experimental measurements presented here are compared with the results of time-dependent wavepacket calculations performed on a set of ab initio potential energy curves. The high level calculations allow prediction of all the dynamical information regarding the dissociation, including electronic polarization effects. Using a combination of theory and experiment it was found that there was negligible cooling of the vibrational degree of freedom of the parent molecule in the molecular beam. The results presented are compared with those following the photodissociation of Cl(2)(v = 0). Although the same electronic states are found to be important for Cl(2)(v = 1) as for Cl(2)(v = 0), significant differences were found regarding many of the observables. The overall level of agreement between theory and experiment was found to be reasonable and confirms previous assignments of the photodissociation mechanism.

Electronic polarization effects in the photodissociation of Cl2

Velocity mapped ion imaging and resonantly enhanced multiphoton ionization time-of-flight methods have been used to investigate the photodissociation dynamics of the diatomic molecule Cl(2) following excitation to the first UV absorption band. The experimental results presented here are compared with high level time dependent wavepacket calculations performed on a set of ab initio potential energy curves [D. B. Kokh, A. B. Alekseyev, and R. J. Buenker, J. Chem. Phys. 120, 11549 (2004)]. The theoretical calculations provide the first determination of all dynamical information regarding the dissociation of a system of this complexity, including angular momentum polarization. Both low rank K = 1, 2 and high rank K = 3 electronic polarization are predicted to be important for dissociation into both asymptotic product channels and, in general, good agreement is found between the recent theory and the measurements made here, which include the first experimental determination of high rank K = 3 orientation.