Photoionization and Absorption Spectrum of Formaldehyde in the Vacuum Ultraviolet

Abstract

Absorption and photoionization coefficients have been measured for H2CO in the 600–2000‐Å region. Integrated oscillator strengths were determined for a number of strong Rydberg transitions above 1200 Å. From the photoionization curve the first adiabatic ionization potential was found to be 10.87±0.01 eV. As an aid in interpreting the absorptionspectrum,theoretical calculations were made using a single‐configuration self‐consistent field procedure for the Rydberg states and a model which included mixing between the Rydberg and valence states. On this basis, weak absorption features between 1340 and 1430 Å have been assigned to the 1 B 1 (σ → π * ) valence state. The 1A 1 (π → π * ) valence state is deduced to be strongly autoionized just above the 2 B 2ionization limit.