Observation of hyperfine quantum beats in two-color laser-induced grating spectroscopy of nitric oxide

Excited-state Structure and Dynamics of Nitric Oxide probed by Resonant Four-wave Mixing Techniques

“…The oscillations are a type of quantum beat with a frequency equal to the energy separation between two coherently excited levels. Accordingly, the oscillation period of 15·8 ns agrees well with the expected energy separation between the F' = 1· 5 and 0·5 hyperfine levels of the A 2I;+, v' = 0, J' = 0·5 state, on the basis of the energy separation observed, 62· 1 MHz, for the equivalent states in the v' = 1 level (McCormack et al 1994). Remarkaby, this measured energy separation is smaller by more than two orders of magnitude the bandwidth of the nanosecond pulsed lasers used.…”

“…In addition, two-colour LIGS in a supersonic molecular beam was used to study the time evolution of laser-induced gratings in NO (McCormack et al 1994). By varying the delay between the grating-forming laser pulse and the grating-probing laser pulse, quantum beats due to the hyperfine structure of the· A 2E+, Vi = 0 state were observed in the LIGS signal for specific polarisation configurations of the input laser beams.…”

“…By varying the delay between the grating-forming laser pulse and the grating-probing laser pulse, we observed quantum beats due to the hyperfine structure of the A 2L;+, v' = 0 state in the LIGS signal for specific polarisation configurations of the input laser beams (McCormack et al 1994). Depending on the polarisation configuration, the two-colour LIGS signal either decayed monotonically as a function of probe delay, reflecting residual motion in the molecular beam and the lifetime of the grating-forming state, or showed oscillatory behaviour as a function of the delay of the probe laser in addition to the smooth decay.…”

“…For example, DFWM has been used to perform background-free transition detection in stimulated-emission spectroscopy (Zhang et al 1992;Vaccaro 1994). Two-colour LIGS has been demonstrated in free jets (Butenhoff and Rohlfing 1992) and used in double-resonance spectroscopy of many stable (Buntine et al 1992(Buntine et al , 1995McCormack et al 1993McCormack et al , 1994McCormack et al , 1995Butenhoff and Rohlfing 1993a;Dunlop and Rohlfing 1994;Wheeler et al 1993) and transient species (Gray et al 1993;Williams et al 1994aWilliams et al , 1995Butenhoff and Rohlfing 1992). In addition to spectroscopy, the time evolution of the transient gratings produced in LIGS has been used as a powerful method to probe inter-and intramolecular dynamics (Rose et al 1987).…”

“…In this paper, we highlight the potential of LIGS for probing excited-state physics by reviewing the results of two double-resonance experiments on NO using two-colour LIGS via the A 2L;, v' = 0 state. Both experiments have been described previously in detail (McCormack et al 1994(McCormack et al , 1995.…”