Photoelectron spectroscopy of rare gas dimers revisited: Vibrationally resolved photoelectron spectrum of argon dimer

Photoelectron spectra of rare gas dimers Ar2, Kr2, and Xe2 have been measured using the He i radiation at 584 A with a resolution of 13 meV. All the six ionic states in the He i region have been resolved for the first time, including some of the purely repulsive states. Ionization energies are presented to an accuracy ≤0.003 eV. Dissociation energies (D0) of the ionic states are calculated using the best estimate adiabatic ionization energies. The D 2Σ1/2g+ states of all the dimers are weakly bound, contrary to an earlier theoretical prediction. Part of the vibrational structure of two of the electronic states of Ar2 has been resolved. For the A 2Σ1/2u+ state, as many as 14 vibrational excitations are observed. These excitations are assigned to transitions to the higher vibrational levels of v=32–45. For the B 2Π3/2g state, three vibrational structures are resolved and are assigned to v=2–4 of the ionic state. Accurate values of the spectroscopic constants of these states are presented. The present values are compared with the values available in the literature. The De values for the A 2Σ1/2u+ and the B 2Π3/2g states are estimated to be 1.361 and 0.104 eV, respectively.