High resolution photodetachment study of OH− and OD− in the threshold region 7000–6450 Å

Abstract

The photodetachment of OH⁻ and OD⁻ ions has been studied in the range 7000–6450 Å, utilizing a tunable, narrow‐bandwidth (0.5–1 Å) dye laser as the light source. A detailed comparison of the observed cross section with model calculations is made, yielding the following results: E.A.(OH)=(14 723±15) cm⁻¹, E.A.(OD)=(14 703±15) cm⁻¹. The observed isotope effect for the electron affinity can be ascribed almost entirely to differences in the position of the ground rotational state in OH(²Π_3/2) and OD(²Π_3/2); the implications of this result for the vibrational frequency of the negative ions are discussed. The energy dependence of the observed cross section indicates the influence of the electron‐permanent dipole moment interaction in the final channel on the threshold behavior, which is found to be sharper than that expected in the absence of such an interaction.