Photophysics of C2- (B2Σ u+) in rare gas lattices: Vibrational relaxation through intermediate a 4Σu+ levels

V. E. Bondybey, L. E. Brus

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Abstract

Time and wavelength resolved fluorescence techniques are used to investigate C2- (B2Σ) radiationless transitions following pulsed, tunable laser excitation. The purely radiative lifetimes in each host are Ne, ≃64 nsec; Ar, ≃40 nsec; Kr, ≃38 nsec; and Xe, ≃34 nsec. The principal B2Σ vibrational relaxation mechanism is a sequential process: crossing into a 4Σ, vibrational relaxation within 4Σ, and reverse crossing into B2Σ. The observed intermediate lifetimes strongly suggest that ν = 04Σ lies between ν = 0 and 1 of B2Σ; this fact allows assignment of gas phase B 2Σ ↔ a4Σ rotational perturbations reported by Herzberg and Lagerqvist. The unperturbed a4Σ constants are Te = 19448.4 cm-1, ωe = 1074.04 cm-1, Be = 1.1348 cm-1, ωexe = 24.68 cm-1, and αe = 0.0035 cm-1. Vibrational relaxation within a4Σ, and intersystem crossing, show a strong multiphonon relaxation energy gap law. The variation in behavior among the 12-12, 12-13, and 13-13 isotopes indicates that the photophysics is dominated by accidental near degeneracies with A2 II (and probably X2Σ) levels in addition to 4Σ levels.

Original languageEnglish
Pages (from-to)2223-2231
Number of pages9
JournalJournal of Chemical Physics
Volume63
Issue number5
DOIs
StatePublished - 1975
Externally publishedYes

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