Photodetachment of an Electron from Selenide Ion; the Electron Affinity and Spin-Orbit Coupling Constant for SeH·

The relative cross section for the gas phase photodetachment of an electron from SeH− has been determined in the wavelength region 428–578 nm (2.90–2.15 eV). An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The cross section exhibits two sharp thresholds, whose positions remain unchanged for the photodetachment of SeD−. As a result, the electron affinity and the spin-orbit coupling constant have been evaluated: E. A. (SeH·)=2.21± 0.03 eV and A (SeH·)=−1815± 100 cm−1.