A weakly bound metastable state of Cr2: Possible evidence for a double minimum ground state

Abstract

When matrix isolated Cr2 molecules are pumped with radiation corresponding to the x 1Σg → A1Σu absorption a new absorption appears belonging to a metastable species of Cr2, whose lifetime ranges between 0.2 to 0.7 s according to the matrix used and the matrix site pumped. A two-color experiment produced the resonance Raman spectrum of this state which in solid argon has vibrational constants ωe=78.6 and ωeXe=0.4 cm−1. The new state is interpreted as being either a member of the ground state manifold of states with high spin multiplicity, or more likely a long-bond form of Cr2 corresponding to the molecule trapped in the outer minimum of a double minimum ground state potential. If so the lifetime observed is the inverse rate of photon-assisted tunneling from the outer to the inner minimum.