OBSERVATION OF HYPERFINE QUANTUM BEATS IN 2-COLOR LASER-INDUCED GRATING SPECTROSCOPY OF NITRIC-OXIDE

Two-color laser-induced grating spectroscopy of NO via the A 2SIGMA+, nu' = 0 state has been used to study the time evolution of population gratings produced in a supersonic molecular beam. For a specific polar ization configuration of the input laser beams, quantum beats due to t he hyperfine structure of the A 2SIGMA+, nu' = 0 state have been obser ved by varying the delay between the grating-forming laser pulses and the grating-probing laser pulse. This form of quantum beat spectroscop y has the advantages of background-free detection, two-color state sel ectivity, a quadratic dependence on the level population, and a beat s ignal independent of the decay mode.