THE ABSOLUTE CROSS-SECTIONS OF PHOTOABSORPTION, PHOTODISSOCIATION, AND PHOTOIONIZATION OF THE GROUP-VIB METAL HEXACARBONYLS AT 300-1600-ANGSTROM

The absolute photoabsorption cross sections sigma(a) and photoionizati on quantum yields eta of Cr(CO)(6), Mo(CO)(6), and W(CO)(6) are measur ed in the wavelength range of similar to 300-1600 Angstrom. We have al so estimated the photoionization cross sections sigma(i) and the neutr al photodissociation cross sections sigma(d) from sigma(a) and eta. Ma in absorption features are tentatively assigned with the help of the M O diagram and the photoeIectron spectroscopic data of M(CO)6(M=Cr,Mo,W ). Large optical oscillator strength distributions and neutral photodi ssociation cross sections are obtained at the photon energies far beyo nd the first ionization potential. Our studies revealed the valence ex citation nature of tile superexcited states in the extreme ultraviolet region. It is suggested that the neutral photodissociation in this re gion shares a similarity with that in the UV region below the first io nization potential because they both involve a repulsive ejection of t he first CO ligand. (C) 1997 American Institute of Physics.