Dititanium and divanadium

Abstract

The Ar+ laser-excited spectrum of matrix-isolated V2 consists of a resonance Raman progression with ωe=537.5 cm−1 and ωexe=4.2 cm−1. With increasing laser power several members of an anti-Stokes progression and sequence components on both Stokes and anti-Stokes members of this progression were observed and attributed to transitions originating from vibrationally excited stated populated as a result of laser irradiation. A second system with ωe=508 and ωexe=3.3 cm−1 also grew in with increasing laser power and 496.5 nm excitation. This was interpreted as a resonance Raman progression within an electronically excited state (A) of V2. The electronic resonance Raman spectrum corresponding to the A→X transition was also observed as well as one to another low-lying electronic excited state. The v′=0 level of state A was found to lie 1860 cm−1 above the v″=0 level of the ground state. The multiple photon nature of the transitions discussed above was determined by performing laser power measurements. The resonance Raman spectrum of Ti2 was excited with HeNe and dye laser illumination in solid argon matrices containing titanium. As with V2, laser irradiation populated excited vibrational states of the ground state, producing an anti-stokes, resonance Raman progression. Isotopic components of Ti2 were resolvable under high resolution, corroborating the assignment. A discussion of multiple bonding in transition metal dimers is presented which shows that the contribution of bonds originating from the atomic d orbitals do not always contribute uniformly to the metal–metal force constant. Hence the formal bond order is not always a good gauge of the bond strength of a transition metal dimer.