Electric-field-induced modulations in photodetachment

Recent observations of the effects of a strong electric field on the photodetachment of ${\mathrm{H}}^{\mathrm{-}}$ are accounted for by a frame-transformation analysis. The only input parameter is the binding energy of the negative ion. An absolute cross section that includes the effects of the field is derived. The cross section shows modulations above the detachment threshold. Further, there is now a nonvanishing value below the zero-field threshold as a result of field-assisted tunneling of the photoelectron.