We have used a colliding-beam method to find two resonances in the photodetachment of electrons from ${\mathrm{H}}^{-}$. A nitrogen laser beam is directed at variable angle across the 800-meV ${\mathrm{H}}^{-}$ beam at the Clinton P. Anderson Meson Physics Facility (LAMPF), resulting in a center-of-mass photon beam wavelength which is continuously tunable from the visible to the vacuum ultraviolet. Our preliminary measurements of the two resonances observed near 11 eV agree well with theoretical predictions within our experimental resolution of 10 meV.

• Received 17 November 1976

DOI:https://doi.org/10.1103/PhysRevLett.38.228