Knowledge Bank

The Xecl(B) excitation spectrum resulting from photoabsorption, XeCl($B,v\prime \leftarrow X,v\prime$), and photoassociation, Xe + $Cl\to XeCl(B,v\prime )$, processes as well as the XeF(B) excitation spectrum are obtained over the spectral ranges of 276..315 nm and $335\dots 360$ 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.$10-28$ $cm8s-1$ 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 nm these values being $41.2.10-16cm2$ and $4.3\cdot 10-28cm6s-1$ respectively.