UV SPECTROSCOPIC STUDIES OF PHOTOEXCITATION TO XeCl(B) AND XeF(B) STATES

Abstract

Author Institution: Institute for Energy Problems Of Chemical PhysicsThe Xecl(B) excitation spectrum resulting from photoabsorption, XeCl($B,v^{\prime} \leftarrow X, v^{\prime}$), and photoassociation, Xe + $Cl \rightarrow XeCl(B,v^{\prime})$, processes as well as the XeF(B) excitation spectrum are obtained over the spectral ranges of 276..315 nm and $335\ldots360$ ran respectively. The double-pulse technique was applied, when the dissociation of halogen molecules by the pulse of the excimer XeCl-laser was followed by the delayed excitation pulse of the tunable dye laser. By measuring the XeCl(B) excitation Intensity dependences on Xe pressure with a dissociating pulse and in the absence of that the contribution Of photoassociative free-bound transitions was determined experimentally. Thus the rate constant of photoassociation, treated as a termolecular (two colliding atoms and a photon) process was estimated to be as high as 1.$10^{-28}$ $cm^{8} s^{-1}$ at the wavelength of 308 nm. The method for excitation spectrum calculations taking properly into account bound-bound and free-bound transitions contributions is developed. The XeCl(B) and XeF(B) excitation spectra are computed and for XeCl the absolute values of the photoabsorption cross- section and the photoassociation rate constant are calculated with at maxima at $^\lambda \approx 308$ nm these values being $41.2.10^{-16} cm^{2}$ and $4.3\cdot 10^{-28} cm^{6} s^{-1}$ respectively