Negative hydrogen ions are exposed to a short infrared laser pulse of 2.15 μm wavelength and 250 fs duration.
An imaging technique is used to record the energy resolved angular distribution of photoelectrons.
The energy spectrum reveals at least three excess photon detachment channels. A quantum interference effect,
resulting in an unusual dependence of the angular distribution on the electron kinetic energy, is most prominent
in the lowest two-photon detachment channel. The appearance of this effect is discussed in terms of the threshold
law of photodetachment. ©2001 The American Physical Society