Luminescence spectroscopy of P13 and P3 state atomic mercury isolated in solid Ar, Kr, and Xe

Abstract

Multicomponent emission bands are recorded for the P13→S01 transition of atomic mercury isolated at single sites in solid Ar, Kr, and Xe matrices. A blueshift observed at elevated temperatures on the 273 nm emission of Hg/Xe is identified in line shape analysis as arising from decreasing intensity of the central component in the band profile. The origin of the multiple components in the emission bands is ascribed to the existence of several vibronic modes which lead to excited state stabilization in the Hg(3P1)/RG matrix systems. A detailed description of these modes and their energetics is presented in the paper directly following. Photoexcitation of the P13 state also yields small amounts of P03 state emission. Hg atom P13 to P03 state intramultiplet relaxation (IMR) is most efficient in Hg/Xe where the ratio of this relaxation channel to P13 state radiative decay is 1/200 as established in time-integrated emission spectra. Despite the weakness of IMR, pulsed laser excitation combined with photon counting detection provide time-gated P03 state emission spectra largely free of the more intense P13 state emission. Such emission spectra recorded under high resolution for the P03→S01 transition of atomic mercury isolated in solid Xe provide the first example of the occurrence of a zero-phonon lines for a metal atom isolated in a rare gas matrix. Wp line shape analysis conducted on the emission bands recorded at specific temperatures, confirm this assignment. The electron–phonon coupling strength (Huang-Rhys, S factor) extracted in the line shape fits for the Hg/Xe transition is 1.3. Slightly stronger coupling is identified in Kr (S=2.2) and stronger still in Ar (S=3.3). Analysis of the diatomic Hg⋅RG potential energy curves reveal that the origin of the weak electron–phonon coupling lies primarily in the similarity in the ground and excited states, but also indicates the site size offered by the host solid plays a role.