Knowledge Bank

Photographic absorption spectra of a flash-photolysed mixture of Xe (750 Torr) and $F2$ (50 Torr) show extended band structure for both B-X (294 - 355 nm) and D-X (239-265 nm) transitions of XeF. Despite extensive overlapping by hot bands, we determined the R-variation of both B-X and D-X transition moments using ``band-cluster analysis’’, in which both cold and hot bands within a given wavelength region are shown to have quite similar R-centroids. We find that the B-X moment is independent of R between 2.30 and 2.54 A; normalizing to the $measured1$ radiative lifetime of $19.4\pm 1$ nsec for $\nu \prime =o$ of XeF(B(1/2)), the transition moment is $2.70\pm 0.22$ Debye in this range of R. Since B-X and D-X absorptions were recorded on the same exposure, the absolute D-X moment could be determined, and varies linearly from 2.255 Debye at 2.25 A to 2.413 Debye at $2.50A(\pm 15$. The computed radiative lifetime of XeF (D(1/2), $\nu^{\prime}= $o) is $10.0\pm 2$ nsec.