Knowledge Bank

The feasibility of optical detection of rotational transitions has been established in a microwave optical double resonance experiment on $BaO.1$ Laser excited fluorescence is used to monitor the population of a ground state rotational level. This population is altered by applying a microwave field at the frequency of a rotational transition involving the monitored level. Typical linewidths (FWHM) of 3.5 MHz are observed with no apparent dependence on pressure (0.02 to 2 torr). The linewidth is broadened by increased laser or microwave power density. An investigation is under way to determine factors contributing to the signal-to-noise ratio in microwave optical double resonance experiments. Fluorescent intensity is sufficient to allow resolution of individual rotational lines, thus transitions due either to a resonant microwave field to collisions can be observed in the excited state. Specifically we hope to report the observation of the $J\prime =3\to 2$ transition in the $A1\Sigma (v\prime =7)$ electronic excited state. This work was supported in part by Army Grant No. DA-ARO-D-31-124-71-G179, NSF Grant No. GP-24373, and AFOSR Grant No. AFOSR-70-1851.