Degenerate four-wave mixing spectroscopy of the (glyoxal) 2 van der Waals complex

Abstract

Glyoxal dimer generated in a supersonic expansion can be detected through the relatively weak glyoxal A → X transition by using degenerate four-wave mixing spectroscopy. A detection limit on the order of 10 11 molecules/cm 3 is obtained. The spectrum can be simulated with a simple N 2 0σ n ( n=2−4) intensity dependence, where N 0 is the ground-state population and σ is the absorption cross section. Inclusion of nondegenerate grating scattering effects due to congestion of transitions within the laser bandwidth improves the spectral simulation. The rotational constants obtained from a rotational band contour analysis are reported for the dimer.