Rotational photodetachment spectroscopy of theSeH−ion

Individually resolved rotational photodetachment thresholds have been observed for ${\mathrm{SeH}}^{\mathrm{-}}$ ions in a magnetic field. The observed photodetachment cross section exhibits structure due to the cyclo- tron levels of the detached electron in the magnetic field. The electron affinity of SeH and the rotational constants of ${\mathrm{SeH}}^{\mathrm{-}}$ are determined from the measured rotational threshold energies. In addition to the high-resolution individual rotational threshold spectra, low-resolution spectra, for which the rotational band structure dominates, are obtained. These low-resolution spectra are used to assign rotational quantum numbers to the individual thresholds. The electron affinity of SeH is found to be 17?5.17(20) ${\mathrm{cm}}^{\mathrm{-}1}$, and the rotational constants of ${\mathrm{SeH}}^{\mathrm{-}}$ are found to be B=7.7289(46) ${\mathrm{cm}}^{\mathrm{-}1}$ and D=3.33(9)×${10}^{\mathrm{-}4}$ ${\mathrm{cm}}^{\mathrm{-}1}$.