Observation of high-nRydberg series (7<n<40) of theH3molecule

Four series of Rydberg states converging to vibrationally excited ${\mathrm{H}}_3$ ${\mathrm{}}^{+}$ have been excited from long-lived levels of ${\mathrm{H}}_3$ in a fast (1.5 keV) molecular beam and have been observed to autoionize to ${\mathrm{H}}_3$ ${\mathrm{}}^{+}$+e. A fifth Rydberg series converging to ${\mathrm{H}}_3$ ${\mathrm{}}^{+}$ in its ground vibrational state has been detected through field ionization. A first analysis of the ionization potentials, quantum defects, and the nature of the long-lived species of ${\mathrm{H}}_3$ is presented.