The low-lying electronic states of KrXe+ and their potential energy functions

Abstract

Photoionization and pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of KrXe have been recorded between 94,800 and 108,000 cm−1 following resonance-enhanced two-photon excitation via selected vibrational levels of the C 0+ and D 1 Rydberg states of KrXe. The PFI-ZEKE photoelectron spectra consist of three vibrational progressions corresponding to the transitions to the X 1/2, A1 3/2 and A2 1/2 states of KrXe+. The photoionization spectra of KrXe reveal long progressions of autoionizing Rydberg states converging to the lowest vibrational levels of the A1 3/2 state of KrXe+. PFI-ZEKE photoelectron spectra of the B 1/2 and C2 1/2 states of KrXe+ have been recorded in the range 111,900–112,700 cm−1 via selected vibrational levels of a Rydberg state of KrXe located in the vicinity of the Kr*([4p]55s[3/2]1) + Xe(1 S 0) dissociation limit. From the observed progressions, adiabatic ionization energies, dissociation energies, and vibrational constants have been derived. A global potential model which explicitly treats the effects of the spin-orbit, the charge-exchange and the long-range interactions was used to obtain potential energy functions for all six low-lying electronic states of KrXe+ from the experimental positions of the vibrational levels of the X 1/2, A1 3/2, A2 1/2, C1 3/2 and B 1/2 states of KrXe+. A comparison of the potential energy curves and of the corresponding dissociation energies and equilibrium internuclear distances of the six low-lying electronic states of ArXe+, KrXe+ and Xe+ 2 enables one to quantify the contribution of the charge-exchange interaction to the chemical bonds in these ions. The dissociation energies of the ground electronic state increase rapidly from ArXe+ (D e = 1480.3 cm−1 [J. Chem. Phys. 128, 014306 (2008)]), for which the charge exchange is weak and non-resonant, to Xe+ 2 (D e = 7932.7 cm−1 [J. Chem. Phys. 121, 8279 (2004)]), for which the charge exchange can be regarded as being resonant.