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    Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices - CCSD(T) calculations and atomic site occupancies


    Davis, Barry and McCaffrey, John G. (2016) Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices - CCSD(T) calculations and atomic site occupancies. Journal of Chemical Physics, 144 (4). 044308. ISSN 0021-9606

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    Abstract

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y1P←a1S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm−1). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.

    Item Type: Article
    Keywords: Potential-energy Curves; Electronic Structure; Luminescence Spectroscopy; Emission Spectra; Ca; Pseudopotentials; Molecules; Ar;
    Academic Unit: Faculty of Science and Engineering > Chemistry
    Item ID: 12551
    Identification Number: https://doi.org/10.1063/1.4940688
    Depositing User: Dr. John McCaffrey
    Date Deposited: 09 Mar 2020 17:06
    Journal or Publication Title: Journal of Chemical Physics
    Publisher: American Institute of Physics
    Refereed: Yes
    URI:

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