Autoionizing Rydberg states in triplet molecular hydrogen.

Abstract

We report the first observation of the autoinizing triplet $\mathrm{nd}$ series of ${\mathrm{H}}_{2}$ covering the region from $n=10$ to the series limit. The autoionizing states are produced by excitation of ${\mathrm{H}}_{2}$ $c^{3}\ensuremath{\Pi}_{\mathrm{u}}^{\ensuremath{-}}$ molecules in a fast (1 keV) beam with a frequency-doubled pulsed dye laser, and the resulting ${\mathrm{H}}_{2}^{+}$ ions are detected. We have also resolved members of the high-lying $\mathrm{nd}$ series ($25<n<35$) converging to the lowest vibrational state of the ${\mathrm{H}}_{2}^{+}$ ion by field ionization. A qualitative interpretation of the spectra in terms of a noninteracting single-channel Rydberg electron model is given.