The photodetachment of OHminus;and ODminus;ions has been studied in the range 7000ndash;6450 Aring;, utilizing a tunable, narrowhyphen;bandwidth (0.5ndash;1 Aring;) 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)equals;(14 723plusmn;15) cmminus;1, E.A.(OD)equals;(14 703plusmn;15) cmminus;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(2Pgr;3sol;2) and OD(2Pgr;3sol;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 electronhyphen;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.
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