Doped rare gas clusters up to completion of first solvation shell, CO2-(Rg)n, n = 3-17, Rg = Ar, Kr, Xe

TL;DR

This study investigates the spectra of CO2-doped rare gas clusters up to the completion of their first solvation shell, revealing structural details and vibrational modes through experimental spectroscopy and comparison with theoretical models.

Contribution

It provides detailed experimental spectra of CO2 in rare gas clusters up to the first solvation shell, including rotational constants and vibrational shifts, with insights into cluster symmetry and structure.

Findings

Identification of specific cluster sizes with symmetric structures

Observation of vibrational modes indicating cluster dynamics

Completion of the first solvation shell at n=17 for Ar clusters

Abstract

Spectra of rare gas atom clusters containing a single carbon dioxide molecule are observed using a tunable mid-infrared (4.3 micron) source to probe a pulsed slit jet supersonic expansion. There are relatively few previous detailed experimental results on such clusters. The assigned clusters include CO2-Arn with n = 3, 4, 6, 9, 10, 11, 12, 15, and 17, as well as CO2-Krn and -Xen with n = 3, 4, and 5. Each spectrum has (at least) partially resolved rotational structure, and each yields precise values for the shift of the CO2 vibrational frequency (nu3) induced by the nearby rare gas atoms, together with one or more rotational constants. These results are compared with theoretical predictions. The more readily assigned CO2-Arn species tend to be those with symmetric structures, and CO2-Ar17 represents completion of a highly symmetric (D5h) solvation shell. Those not assigned (e.g. n = 7, 13) are probably also present in the observed spectra, but with band structures which are not well-resolved and thus not recognizable. The spectra of CO2-Ar9, -Ar15, and -Ar17 suggest the presence of sequences involving very low frequency (~2 cm-1) cluster vibrational modes, an interpretation which should be amenable to theoretical confirmation (or rejection).