Photoabsorption of Kr₂⁺ in the ultraviolet: Revisited

The photoabsorption spectrum of the Kr₂⁺ ground electronic state (X²Σ_u⁺) has been measured in the ultraviolet (257-355 nm) by a fluorescence suppression technique. Peak absorption is recorded at ∼330 nm and the spectral width of the observed continuum is ∼60 nm (FWHM) which is ∼25% smaller than the value predicted by theory for a Kr₂⁺(X) vibrational distribution thermalized at 300 K. Similar experiments with Ar/Kr mixtures: (1) reveal weak absorption attributed to ArKr⁺ peaking at ∼280 nm, and (2) suggest that the ArKr⁺ ion is rapidly converted to Kr ⁺ by a displacement reaction.