Knowledge Bank

Diode laser spectra of slightly cooled $(256K)UF6$ gas at 3.5 torr were obtained in the $1875cm-1(3\nu 3)$ region using a 10-m White-type cell built by Kim $etal..1$ in which multiple reflections provided path lengths of 360-400 m. Some of these spectra were reported $earlier.2$ Despite the intrinsic weakness of this absorption and the presence of very numerous hot bands at this temperature, we have identified several discrete features as belonging to the transition out of the ground state and have assigned their rotational quantum indices. The wavenumbers were fitted to the vibration-rotation Hamiltonian of $Hecht3$ using an interacting-band $analysis.4$ Derived values for $B\zeta 3$ and $△B$ are consistent with corresponding values determined from the analysis of the $\nu 3fundamental.5$ In addition, we now report Hecht's parameters $w30.X33.G33$. and $T33$ for the $n\nu 3$ vibrational overtone ladder of $UF6$. The implied ladder structure will be discussed in terms of a local-type'' vs, a normal-type'' interpretation of the $\nu 3$ mode of vibration.