Absorption of electronically excited Xe2Cl in the ultraviolet

A. W. McCown, M. H. Ediger, D. B. Geohegan, J. G. Eden

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The absorption cross section for the lowest-lying, bound excited state (4 2Γ) of Xe2Cl has been measured at several wavelengths in the ultraviolet (UV). Temporally isolating the excited Xe 2Cl species in Xe/Cl2 gas mixtures has been accomplished by producing XeCl molecules in the B state by photoassociation [Xe+Cl+ℏω→XeCl(B)] at λ=308 nm. Collisional mixing of the lowest lying ion pair states of the excimer subsequently forms the XeCl species in its C state. Following the formation of Xe2Cl* from XeCl(B,C) by a three-body collision, the long radiative lifetime of the trimer (>200 ns) relative to those for the XeCl B and C levels is exploited to ensure that the triatomic molecule is the predominant species when the experiments are performed. A second UV laser pulse depletes the Xe 2Cl(4 2Γ) population by photoexcitation [as evidenced by the sudden suppression of the 4 2Γ→1 2Γ blue-green (λ∼485 nm) fluorescence] and the absorption cross section is determined from the dependence of the degree of fluorescence suppression on the laser intensity. Contrary to the known Xe 2+ 1(1/2)u→2(1/2)g UV absorption profile, Xe2Cl(4 2Γ) exhibits significant absorption at wavelengths as low as 193 nm, whereas the dimer ion absorption at 248 nm is only a fraction of its peak (λ∼340 nm) value. Photoionization of excited Xe2Cl at wavelengths below ∼275 nm may be responsible for the cross sections measured for photon energies as large as 6.4 eV.

Original languageEnglish (US)
Pages (from-to)4862-4866
Number of pages5
JournalThe Journal of Chemical Physics
Issue number11
StatePublished - 1985

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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