Structure of the photodetachment cross section in a magnetic field: An experiment with OH^-

Photodetachment from OH^- in a magnetic field has been studied experimentally using light with energies between 14400 and 14900 cm^-1. Presented here are high-resolution data which exhibit sharp magnetic field structure at thresholds and low-resolution data which show monotonically increasing cross sections. The current work is the first in any atomic or molecular system where sufficient energy resolution has been achieved to observe the shape of the cross section in a magnetic field.