Photoionization with molecular beams. I. Autoionization structure of nitric oxide near the threshold

Abstract

The photoionization efficiency curve of NO+ (X1Σ+) was obtained using a molecular beam technique in the wavelength range from 1350 to 1185 Å (9.18–10.46 eV). Due to the lowering of the rotational temperature by supersonic expansion, the autoionization structure superimposed on the vibrational steps is well resolved. This structure is attributed to vibrational autoionization. The splitting of the autoionization peaks due to the spin–orbit ground state (2Π1/2, 2Π3/2) of nitric oxide is observed. The strong intensity peaks of the vibrational autoionization are found to correspond to a vibrational quantum number change of Δv=−1. The autoionization structure observed on the first four vibrational steps obeys the propensity rule proposed by Berry.