Photodissociative excitation processes of XeF2 in the vacuum ultraviolet region 105–180 nm

Abstract

Photodissociative excitation processes of XeF2 are studied by absorption and photofragment fluorescence spectroscopies in the vacuum UV region 105–180 nm. The quantum yields are measured along with the dispersed fluorescence spectra for emissions from XeF* (B, C, and D) excimers formed from XeF2 excited by linearly polarized, monochromatized synchrotron radiation. Fluorescence anisotropy, R, of XeF* fragment emission was also measured against excitation light wavelength in the region 105–165 nm. The quantum yields for XeF* excimer formation are found to be very high; especially in the valence band region shorter than 130 nm it reaches almost unity. From the fluorescence measurements we have observed new peaks assigned to 5πu→5dR Rydberg transitions. The intense 5πu3/2→6sR bands which appear around 143 nm exhibit no fluorescence excitation bands; even fluorescence dips are observed at 143.18 and 144.25 nm whereas very weak positive fluorescence bands are observed at 141.04 and 142.11 nm. The R values for the very broad valence bands which underlie intense Rydberg bands are found to be high. The 5πu series of Rydberg bands exhibit low R values. Based on the energetics and the results of quantum yields and fluorescence anisotropy values, the valence and Rydberg bands observed are assigned from the viewpoint of symmetry of the excited state, and the dynamics of the dissociation processes is discussed.