Dissociation processes of core-excited CBr 4 involving the Br(3d, 3p, 3s) and C(1s) inner-shells in the range 50–460 eV

Abstract

The dissociative multiple photoionization of CBr 4 in the valence, and in the Br(3d, 3p, 3s) and C(1s) inner shell regions has been studied by using time-of-flight (TOF) mass spectrometry coupled to synchrotron radiation in the range 50–460 eV. Total and individual photoion yield curves have been recorded as a function of the photon energy. Several discrete resonances are observed below the Br(3d) threshold region. Also a giant shape resonance in the total ion yield curve is observed beyond the Br(3d) region, which can be identified as a shape resonance owing to the diffusion of the outgoing photoelectron by the angular momentum barrier in the 3d 9ϵf outgoing channel. Various monocations of Br + and CBr n + ( n=0–3) are detected along with dications of Br 2+ and CBr 3 2+ in the whole energy range examined. Dissociation processes of multiply charged CBr 4 parent ions have also been investigated by photoelectron–photoion coincidence (PEPICO) and photoion–photoion coincidence (PIPICO) methods. The dominant dissociation pattern is found to involve C +–Br + and Br +–Br + in the whole energy range examined. Distinct energy dependence of dissociation processes is observed in the Br(3p) and Br(3s) regions. With the help of ab initio HF/6-311++G(d) calculation, we estimated the photoabsorption positions and symmetries for the discrete core-excited states using the Z+1 equivalent ionic core model. The specific excitation and dissociation of molecules provides information on energy dissipation processes in conjunction with the relevant core hole states.