Observation of resonance effects in the relative partial photoionization cross sections of the d bands of M(CO)6, M = Cr,Mo and W

Relative partial photoionization cross sections as a function of photon energy, over the range 20–110 eV, have been measured for the valence bands of Cr(CO)₆, Mo(CO)₆ and W(CO)₆. All three t_2g⁻¹ bands show a very pronounced increase in intensity at photon energies (hv) corresponding to np resonant absorption (Cr(CO)₆, hv = 52.5 eV, n = 3; Mo(CO)₆,hv = 48 eV, n = 4; W(CO)₆, hv = 44 and 53 eV, n = 5). The other valence bands show a small intensity increase at similar energies. Observation of such resonant photoemission provides an unambiguous method for assignment of nd bands in the photoelectron spectra of gas-phase molecules.