Absorption spectrum of (ArKr)* in the ultraviolet

Abstract

Recent experiments reported by Pratt, Dehmer, and Dehmer have examined the electronic structure of NeXe, ArXe, and KrXe in the vicinity of the separated atom limits by resonantly enhanced multi photon ionization. However, little is known of the rare gas hetero-nuclear molecules near the potential minima of the Rydberg states. This paper describes experiments in which the absorption spectrum of the lowest electronic excited state of ArKr has been studied by inter-Rydberg laser spectroscopy. Specifically, excited Kr atoms are first produced by two-photon excitation of the Kr 6p[3/2]2 state at 103,363.4cm-1 in a mixture of 1040-TorrAr and 40-TorrKr(300 K pressures). Following the rapid relaxation of the 6p atoms into the 5s states, ArKr excited molecules are formed by three-body molecule collisions of Kr(5s) with two ground state Ar atoms. An adjustable time after the arrival of the first laser pulse (typically 700 ns), a dye laser beam excites the ArKr species to a higher-lying Rydberg state. Dissociation of the highly excited molecule is detectable by observing Kr atomic emission at 820 nm. A highly-structured band that is attributed to ArKr has been observed near 372 nm. Temporally resolved and pressure-dependent studies of this band show clearly that it is associated with neither Kr2 nor Ar2. The identification of this band as well as the remainder of the molecule’s UV absorption spectrum is discussed.