Knowledge Bank

We have detected supersonic molecular beams of LiH and NaH using the laser fluorescence technique. By direct measurement of the fluorescence decay of excited $A1\Sigma +$ state molecules after pulsed dye laser excitation we have determined radiative lifetimes of several vibration-rotation levels. We find $\tau (\nu \prime =2,J\prime =3)=29.4\pm 1.3,-(\nu \prime =5,J\prime =3)=30.5 \pm 1.3$ and $\tau (\nu \prime =7,J\prime =12)=36.9 \pm 1.9$ nsec for LiH and $\tau (\nu \prime =8,J\prime =3)=22.7 \pm 1.6$ nsec for $\mathrm{<mrow\; data-mjx-texclass="ORD">23</mrow>}NaH$, with the quoted uncertainties representing three standard deviations. Recently Wine and Melton have measured LiH radiative lifetimes using dye laser excitation of LiH generated in a heat pipe oven. The agreement with the present results is very good. It is also very pleasing to note that these experimental values agree to within the $\sim 10$ quoted experimental uncertainties with theoretical lifetimes obtained using ab initio transition moments which Docken and Hinze (LiH) and Sachs, Hinze, and Sabelli (NaH) have calculated from multi-configuration self-consistent-field (MCSCF) wavefunctions. Acknowledgment is made to the Donors of The Petroleum Research Fund, administered by the American Chemical Society, and to the National Science Foundation for support of this research.