Molecular Spectroscopy by Stepwise Two-Photon Ion-Pair Production at 71 NM

摘要

The Rydberg states of H sub 2 have been a continuing subject of intensive study by various research groups. However, understanding of the high lying electronic states of this molecule has been inhibited by the lack of spectroscopic data in the region <75 nm. Experimental studies have been difficult because spectroscopic features are generally buried under an intense absorption or photoionization continuum. Intense, high-resolution excitation sources are not easily available. Recent developments on tunable, narrowband, coherent xuv sources provide new means of studying the spectroscopy in this region with high resolution (+- .0005 nm). We have applied the technique of stepwise two-photon excitation to study photoionization of H sub 2 in a molecular beam using the two lowest excited states of H sub 2 as the intermediate level. This excitation, coupled with the detection of background-free H exp - ions has enabled us to uncover, for the first time, spectroscopic features that are difficult to observe in positive ion detection. These features have been successfully assigned to new Rydberg series converging to the high vibrations of the H sub 2+ ground electronic state. (ERA citation 11:004215)