We demonstrate velocity measurements of gas-phase particles by using cavity ringdown spectroscopy (CRDS). Velocity information is inferred from the Doppler-shift contributions to the measured absorption line shape. Because in CRDS the laser beam propagates back and forth within the optical cavity, a measured absorption feature is both upshifted and downshifted; i.e., it is split by the velocity component parallel to the optical axis. The splitting of the absorption features allows direct velocity measurements to be made without requiring an external frequency reference. The CRDS velocity measurement approach is demonstrated for sputtered molybdenum atoms in a low-pressure (collisionless) environment.
© 2005 Optical Society of America
A. P. Yalin and V. Surla, "Velocity measurements by cavity ringdown spectroscopy," Opt. Lett. 30, 3219-3221 (2005)