Laser diagnostic in molecular beams

Abstract

The output from a stabilized, tunable single-mode laser is split into two beams which cross the molecular beam perpendicularly and at an angle of β to the beam axis. Tuning the laser frequency across the unshifted and Doppler-shifted absorption profile of the molecular transition yileds the velocity distribution of the molecules in the beam for individual quantum states. The internal state distribution among vibrational and rotational levels in the beam can be determined by comparing the fluorescence simultaneously induced in the beam and in a cell with molecules in thermal equilibrium.