Abstract

Gas-phase multiphoton electronic excitation and ionization in ammonia have been extensively studied in recent years. ^1,2 The discovery of several electronic states by three-photon absorption (four-photon ionization) has intensified interest in this simple but important molecule.¹ Our experiments, which involve two-photon resonant excitation of various vibronic states, have led to two significant discoveries. We report the first observation of fluorescence from excited electronic levels of ammonia and, at pressures greater than ~200 Torr, report the discovery of a novel high-gain molecular-gas laser. Here simultaneous two-photon absorption excites a vibronic level of the NH3 C state from which stimulated emission (in the visible) occurs down to a vibronic level of the predissociative A state.

© 1983 Optical Society of America