Emission, optical–optical double resonance, and excited state absorption spectroscopy of matrix isolated chromium and molybdenum atoms

Making use of a combination of time-resolved emission, optical–optical double resonance, and excited state absorption spectroscopy, it has been possible to assign virtually all spectral features with energies below the z7P0 state of matrix isolated Cr atoms. The a5S state located at 7593 cm−1 in the free gaseous Cr atom has lifetimes of 6.32 and 5.1 s in Ar and Kr matrices, respectively. Matrix perturbations on Cr emission lines are small (<±100 cm−1). The dependence of nonradiative decay rates on the local density of states is elucidated. The magnitude of matrix shifts for a particular transition is correlated with the electronic configurations of ground and excited states and it is pointed out that states having only ‘‘s’’ electrons in addition to ‘‘d’’ electrons maintain their gas phase energy relationships in the matrix environment. Direct fluorescence is observed from the z7P0 level of Mo to the 7s ground state. The spin-orbit splitting of the ‘‘relaxed’’ z7P0 state is 690 cm−1, slightly lower than the 707 cm−1 splitting of the free gaseous Mo atom.