The reactive metallocenes, tungstenocene and molybdenocene (M(η5-C5H5)2; M = Mo, W), have been generated by photolysis of the corresponding dihydride complexes, M(η5-C5H5)2H2, in argon and nitrogen matrices at 12 K. The metallocenes have been probed by laser-induced fluorescence with a pulsed tunable laser and by UV/vis absorption spectroscopy. Structured emission is observed from the LMCT excited states (lifetimes < 10 ns). The spectra are complicated by multiple sites/conformers, but emission spectra of a single site/ conformer may be obtained with appropriate selection of matrix and excitation wavelength. Corresponding excitation spectra are measured from the area of selected emission peaks as a function of excitation wavelength. Vibrational progressions are dominated by the ring-metal-ring symmetric stretching mode (v4 ≈ 300 cm-1). Nevertheless, this mode changes in frequency by ≤4 cm-1 (≤1.3%) in the LMCT excited state. The best-resolved peaks have a full width at half-maximum of ca. 10 cm-1. Most of the emission is vibrationally fully relaxed, but weak emission peaks arising from v′ = 1 states are found for MoCp2 in N2 matrices. © 1995 American Chemical Society.