The absolute cross sections of photoabsorption, photodissociation, and photoionization of the group VIB metal hexacarbonyls at 300–1600 Å

Abstract

The absolute photoabsorption cross sections σa and photoionization quantum yields η of Cr(CO)6, Mo(CO)6, and W(CO)6 are measured in the wavelength range of ∼300–1600 Å. We have also estimated the photoionization cross sections σi and the neutral photodissociation cross sections σd from σa and η. Main absorption features are tentatively assigned with the help of the MO diagram and the photoelectron spectroscopic data of M(CO)6(M=Cr,Mo,W). Large optical oscillator strength distributions and neutral photodissociation cross sections are obtained at the photon energies far beyond the first ionization potential. Our studies revealed the valence excitation nature of the superexcited states in the extreme ultraviolet region. It is suggested that the neutral photodissociation in this region shares a similarity with that in the UV region below the first ionization potential because they both involve a repulsive ejection of the first CO ligand.