Absorption Spectrum of H2 in the Vacuum-uv Region. I. Rydberg States and Ionization Energies

Abstract

The absorptionspectrum of molecular hydrogen has been investigated in the 950–700‐Å region with a 6.65‐m normal‐incidence spectrograph in the second order with the helium continuum as background. Seventeen Rydberg series are identified. Fourteen belong to npπ 1 Π u ← X 1 Σ g + transitions and consist of Q(K) lines which converge to levels υ = 0–5 of the ground state of H2 +. The other three series belong to npσ 1 Σ u + ← X 1 Σ g + transitions and consist of P(1) lines for two of the series, and R(0) lines for the third. The lowest ionization energy of H2, obtained from the Q(K) line series analysis, is 124 417 ± 2 cm−1 less than the previously accepted value by 12 cm−1. The autoionization effects observed by Beutler and Jünger in the (6, 0) band of the D 1 Π u ← X 1 Σ g + system are discussed.