Vacuum ultraviolet absorption spectra of the van der Waals molecules Kr2 and ArKr

Abstract

The vacuum ultraviolet absorption spectrum of the van der Waals dimer Kr2 has been photographed in the region 1050–1260 Å by a 6.65 m spectrograph with the argon continuum as background source. Eight band systems, four well-developed and four rather fragmented, are observed. Vibronic analyses of the former four systems reveal that their upper states are correlated to separated atom limits in which one Kr atom is excited to various levels of configuration 4p55s. Upper molecular state designations and dissociation limits are discussed. The four fragmented band systems are energetically close to various KrI levels of configuration 4p55p. A similar study of a mixture of argon and krypton yields five groups of diffuse bands attributed to ArKr; two of these band groups are close to KrI resonance lines. The ground electronic state of Kr2 supports 16 bound vibrational levels of which nine (ν″ = 0–8) are involved in the observed vibronic structure and the other seven inferred from an extrapolation procedure based on an assumed inverse sixth power long-range potential. The spectroscopic values for the well depth 138.4 ± 1.9 cm−1 and the zero-point vibrational energy 11.6 ± 0.1 cm −1 are in accord with recent results derived from molecular scattering experiments.