A STUDY OF THE B-1(2) EXCITED-STATE GEOMETRIES OF THE METAL-METAL QUADRUPLY BONDED COMPOUNDS MO(2)X(4)(PME(3))(4) (X=CL, BR OR I)

The excited state geometries of the metal-metal quadruply bonded compo unds Mo(2)X(4)(PMe(3))(4) (X = Cl, Br or I) have been studied by means of resonance Raman and absorption spectroscopy. A fit of the paramete rs of a simple theoretical model to the experimental data indicates th at the metal-metal bond increases some 10 pm on excitation to the B-1( 2) (delta delta) state, whereas other geometric changes are small. Fu rthermore, the phenomenological lifetime factor of the excited state, Gamma, is found to be dependent on the vibrational quantum number, ups ilon, of this state.