Luminescence of Atomic Barium in Rare Gas Matrices: A Two-Dimensional Excitation/Emission Spectroscopy Study

This is the authors' abstract. We don't add key points for this paper.

absorption of barium atoms occupying multiple sites. Two-dimensional excitation/emission scans have also been used in this study to monitor the effects of sample annealing and thereby identify the thermally stable sites of isolation. Sites of the same type occupied by atomic barium in the three host solids are identified in resolved excitation spectra and are associated on the basis of the observed matrix shift versus host polarizability. Following site associations, the photophysical properties of each matrix site were characterized revealing that the Stokes shift was greatest in the blue site, smallest for the violet site, and intermediate for the green site. The emission temperature dependences and excited state lifetimes were recorded, indicating that measured radiative lifetimes of 4-5 ns were in good agreement with the gas phase value of 8.4 ns when corrected for the effective field of the solids. The only exception to this was the blue site in Ba/Xe, where a nonradiative quenching channel exists even at 9.8 K that competes effectively with the nanosecond fluorescence. An unusual, asymmetric 2 + 1 excitation band has been recorded for atomic barium in the three rare gas hosts in addition to the threefold split, Jahn-Teller bands typically observed for P ← S absorptions of matrix-isolated metal atoms. Possible assignments of the sites responsible for these band shapes are made on the basis of recent spectral simulations obtained from molecular dynamics calculations on the Ba/Xe system.