PHOTOABSORPTION UV SPECTROSCOPY OF X-B TRANSITION IN XcCI EXCIMER MOLECULE

Author Institution: Quantum systems Lab., Institute for Energy Problems of Chemical Physics.The excitation spectrum owing to $XeCI(X,v\to B,v')$, photoabsorption, and $Xe +CI \to XeCI(B,v)$, photoassociation, transitions was obtained for the first time in a wide spectral range (276-315 nm). Having been irradiated by the XcCI-cxcimer laser, to obtain Cl atoms, the mixture of Xe (1-4 atm) and C12 (0.5.3 forr) was exposed to the pulse of tunable dye laser second harmonic. The following fluorescence on XcCI(C-A) transition (350 nm) as well as from triatomic Xc2CI excimer molecule (490 nm), formed in secondary, XcCI + 2Xe - Xe2CI + Xc, reaction has been observed. The spectrum consists of v-bands (up to $v=22$) with v* structure and the peaks positions are well-assigned with that observed in emission spectra. For the upper v values a pronounced isotopic. CI-CI, structure is clearly seen. The spectrum red wing, 310-315 nm, behavior shows some evidences for Xe2CI direct photochemical formation. The attempt to divide the contributions of photoabsorption and photoassociation proccsses has been undertaken and the estimate for the rate constant of photon-assisted two-body atomic recombination reaction has been accomplished. The spectrum obtained seems to be of interest for Franck-Condon factors calculations (since the populations of the initial XcCl(B,v) state v.J-sublvels being in equilibrium are well-determined) and for elucidation of the tunable XcCI-Iaser perspectives

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

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