Vacuum ultraviolet spectroscopy of molecules using third-harmonic generation in rare gases

A variety of spectroscopic studies in the vacuum ultraviolet (VUV) region (100–200 nm) has been performed using tunable, narrow bandwidth (∼0.05 Å) light produced by third-harmonic generation in rare gases. These experiments include one-photon absorption and photoionization spectroscopy and photoionization threshold determinations. Two-photon ionization studies of NO, using the VUV light to probe Rydberg states and the fundamental light to ionize are also presented. These studies demonstrate the simplicity and utility of a laser-based, tunable high-resolution source for VUV spectroscopy.