SPECTROSCOPY OF XEF IN AR AND NE MATRICES

Spectroscopic constants for the B2SIGMA+ and C2PI charge transfer states of XeF in Ar and Ne matrices are derived from vibrational progressions in excitation and emission spectra. Polarization effects on the T(e) values are discussed and Rittner potentials are fitted to the constants. Emissions at 389 and 411 nm in Ne and Ar, respectively, are attributed to a distorted B state denoted as B* with a strong red shift of T(e) and an about 30% larger omega(e). B* is assigned to a XeF center with an additional F atom which can be a precursor to XeF2 according to a comparison with Xe2F spectra and the concentration dependence of the intensities. The B* vibrational bands display two well resolved fine structure progressions with a common omega(e) of is similar to 60 cm-1 in Ar and Ne which is close to the maximum matrix phonon density and one with 30 cm-1 in Ne and 15 cm-1 in Ar. A reversible change in the Ne fine structure pattern with temperature can be correlated to a face-centered-cubic-hexagonal close-packed (fcc-hcp) phase transition.