Ultraviolet photoassociative production of XeCl(B,C) molecules in Xe/Cl2 gas mixtures: Radiative lifetime of Xe2Cl(4 2Γ)

Abstract

Electronically excited XeCl molecules are produced directly from xenon and chlorine atoms in mixtures of Xe and Cl2 vapor at room temperature by laser photoassociation at λ=308 nm. The peak intensities of both the XeCl(C→A) and Xe2Cl 4 2Γ→2 2Γ spontaneous emission signals at 350 and ∼485 nm, respectively, are linear in laser fluence and Cl2 partial pressure. Consequently, the XeCl excimer production mechanism is one involving Xe, Cl and one 4 eV photon in which Cl2 is photodissociated on the X 1∑→1Π band throughout the XeCl laser pulse. This conclusion is supported by the enhancements of the XeCl(C) state population of more than 15 that are observed when the Xe/Cl2 mixture is irradiated by an additional ultraviolet (UV) laser pulse [of wavelength 351 nm (XeF), 308 or 193 nm (ArF)] that arrives prior to firing the XeCl laser. The effect is much more pronounced at 193 nm than at the other wavelengths, indicating tht the Cl concentration is augmented by photoionizing Xe, followed by XeCl excimer formation and dissociation of the weakly bound ground state. Also, the radiative lifetime of the Xe2Cl 4 2Γ state was measured to be 245±10 ns.