Knowledge Bank

The $A~-X~$ fluorescence excitation spectrum of HCN has been recorded using 4-wave mixing in Sr vapor as a tunable vacuum ultraviolet source. The excitation spectra are notable for the high signal to noise ratio, resolution of nearly all previously blended lines(FWHM $\sim 0.3cm-1)$ and absolute wavenumber accuracy($0.03cm-1$). Measured lifetimes for the first three bending levels of the $A~$ state qualitatively confirm the unusual trend in predissociation lifetimes reported by Hsu $etal.1$ Stem-Volmer fluorescence quenching studies reported here yield a best fit quenching constant for the $A~(000)1$ level of $Kq=73\mu s/Torr$, which is of the same order of magnitude as the previously reported quenching constant for the $A(010)1$ level. Stark effect measurements of the $A~$-state electric dipole moment now in progress will also be reported.