Absorption of electronically excited Xe2Cl in the ultraviolet

A. W. McCown, M. H. Ediger, D. B. Geohegan, James Gary Eden

Research output: Contribution to journalArticle

Abstract

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
Volume82
Issue number11
DOIs
StatePublished - Jan 1 1985

Fingerprint

Wavelength
absorption cross sections
Fluorescence
retarding
wavelengths
Ions
Ultraviolet lasers
triatomic molecules
fluorescence
Photoionization
Molecules
Photoexcitation
ultraviolet absorption
radiative lifetime
excimers
trimers
ultraviolet lasers
photoexcitation
Excited states
Gas mixtures

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Absorption of electronically excited Xe2Cl in the ultraviolet. / McCown, A. W.; Ediger, M. H.; Geohegan, D. B.; Eden, James Gary.

In: The Journal of Chemical Physics, Vol. 82, No. 11, 01.01.1985, p. 4862-4866.

Research output: Contribution to journalArticle

McCown, A. W. ; Ediger, M. H. ; Geohegan, D. B. ; Eden, James Gary. / Absorption of electronically excited Xe2Cl in the ultraviolet. In: The Journal of Chemical Physics. 1985 ; Vol. 82, No. 11. pp. 4862-4866.
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AB - 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.

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