Vibrational spectroscopy of Xe₂⁺ via pulsed field ionization

Delayed, pulsed field ionization of extremely high-n Rydberg states has been used in combination with a high-resolution vacuum ultraviolet radiation source to measure the vibrationally resolved spectra of the first three bound states of Xe₂⁺. For the ground state of the ion (A ²Σ_u⁺), a long progression beginning at v⁺=56 was observed which included isotopically resolved energy levels. The spectroscopic parameters obtained from a fit of the data to anharmonic oscillator energy levels are reported. The resulting Xe₂ ionization potential is somewhat higher than previously reported. Several vibrations of the first excited state (B ²Π(3/2)g) were observed near 97 000 cm^-1. An absolute vibrational assignment was not possible due to an unusual alternation of intensities. Nevertheless, a lower bound on the binding energy and an estimated vibrational frequency are reported. For the C ²Π_(3/2)u state, the v⁺=0-2 vibrational levels were observed with an intensity distribution consistent with the weakly bound nature of this state. The derived binding energy and vibrational frequency for the C²Π_(3/2)u state are reported.