Up to 30 mW of UV radiation is generated, sufficient to saturate the transitions of interest. Four cm downstream of the nozzle, the molecular beam is skimmed before passing into a second differentially-pumped chamber. One meter downstream, the beam is orthogonally crossed with the UV laser beam.
Additional hardware is included to aid in the analysis of complex spectra.
The control system consists of a lock-in amplifier and PID servo electronics to control the dye laser so that the sideband remains fixed on a peak maximum of the reference cavity at all times. The double-pass configuration of the AOM permits tunability over a full free spectral range of the reference cavity enabling continuous scans over any desired frequency interval with a digital step resolution of 60 kHz. The computer interface controls the laser system. In addition to acquiring the fluorescence photon count and the UV power, the reference cavity transmission signals, the PID dye laser error signal, and the AOM ramp voltages are simultaneously digitized at rates from 500 Hz to 5 kHz. These high digitization rates aid in the removal of low frequency noise from mechanical pump vibrations and acoustic disturbances.