Abstract
Rotational photodetachment thresholds have been observed for SeH- ions in a magnetic field. Assignment and fitting of the thresholds determines the electron affinity and the rotational constants. The electron affinity of SeH is found to be 17845.17(20) cm-1 and the rotational constants of SeH- are B=7.7289(46) cm-1 and D=3.33(9)*10-4 cm-1. The shape of the cross section near threshold and the appearance of oscillations in the cross section provide a test of the understanding of the effect of a magnetic field on the photodetachment cross section.