Negative ion photoelectron spectroscopy of copper hydrides

We report photoelectron imaging spectra of CuH− and CuH 2 - and their deuterated analogs. The CuH− photoelectron spectrum exhibits transitions to the ground (X 1Σ+) and lowest excited triplet (a 3Σ+) and singlet (A 1Σ+) states, with EA(CuH) 0.444(6) eV. The photoelectron spectrum of linear X 1 Σ g + HCuH− is dominated by a transition to the linear excited A 2 Σ g + state with a 2.853 eV binding energy. It is accompanied by an extended unresolved vibrational progression involving the bent CuH2 X 2B2 ground state. Ab initio calculations show a 0.255 eV energy difference between these two states allow determination of EA(CuH2), 2.60(5) eV.