Ti2: Accurate determination of the dissociation energy from matrix resonance Raman spectra and chemical interaction with noble gases

UV-visible and resonance Raman spectra of Ti-2 isolated in Ar, Kr, and Xe matrices at temperatures of 10 K were measured by using the 514 nm line of an Ar ion laser. The data show that the Ti-2 molecule interacts strongly with Xe, leading to a significant weakening of the Ti-Ti bond strength. The f(Ti-Ti) force constant decreases in the series Ar > Kr > Xe, from 232.8 Nm(-1) in Ar and 225.5 Nm(-1) in Kr to 199.7 Nm(-1) in Xe. Additional experiments in an Ar matrix containing 2% of Xe indicate the formation of a molecule of the formula Ti2Xe. Our spectra for Ti-2 in an Ar matrix give evidence for several previously not observed members of the Stokes progression. The sum of experimental data allows for an improved estimation of the dissociation energy on the basis of a LeRoy-Bernstein-Lam analysis. A dissociation energy of 1.18 eV was derived from this analysis. The UV-visible data give evidence of the vibrational levels of an excited state of Ti-2.