Photofragmentation spectra and structures of Sr{sup +}Ar{sub n},thinspn=2{endash}8 clusters: Experiment and theory

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476527· OSTI ID:636140

Fanourgakis, G S; Farantos, S C; Lueder, C; Velegrakis, M ^[1]; Xantheas, S S ^[2]

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1. Institute of Electronic Structure and Laser, Foundation for Research and Technology--Hellas, Iraklion, Crete 711 10 (Greece)
2. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 906 Battelle Boulevard, P.O. Box 999, MS K1-96, Richland, Washington 99352 (United States)

The total photofragmentation cross sections of size selected Sr{sup +}Ar{sub n},n=2{endash}8, clusters have been recorded in a time of flight (TOF) mass spectrometer. In the energy range of 21thinsp000{endash}27thinsp000 cm{sup {minus}1} three absorption bands are observed that are attributed to transitions from the ground to the three excited states that correlate to the 5p orbitals of strontium. No vibrational structure in the spectral bands is observed, even in regions where the spectrum is recorded with a resolution of 1 cm{sup {minus}1}. The absorption spectra are calculated within a semiclassical approximation. Accurate {ital ab initio} calculations for the ground Xthinsp{sup 2}{summation} and the Athinsp{sup 2}{product} and Bthinsp{sup 2}{summation} excited states of Sr{sup +}Ar are combined with a perturbative one-electron model, which includes the spin{endash}orbit coupling, to construct potential energy surfaces for the excited states of all clusters. The theoretical spectra obtained without using any adjustable parameters reproduce the patterns and trends of the experimental spectra, but they are shifted to higher frequencies. A better agreement between theoretical and experimental spectra is obtained by adjusting the depth of the potential wells of the ground Xthinsp{sup 2}{summation} and excited Athinsp{sup 2}{product} states of the Sr{sup +}Ar dimer to the experimentally estimated values. From both calculations we conclude that Sr{sup +}Ar{sub 3} is a trigonal pyramid of C{sub 3v} symmetry and Sr{sup +}Ar{sub 6} has a C{sub 5v} symmetry with five argon atoms forming a regular pentagon, one argon atom below and the cation above the pentagon plane. For these clusters, theory reproduces the characteristic blue shifts found in the absorption spectra and the splittings of the doubly degenerate states encountered in these symmetric complexes. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 636140
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 109; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ARGON
ARGON COMPLEXES
ATOMIC CLUSTERS
CATIONS
DISSOCIATION
EXCITED STATES
FRAGMENTATION
GROUND STATES
MOLECULAR CLUSTERS
PHOTOLYSIS
STRONTIUM
STRONTIUM COMPLEXES