Radiative lifetimes of the A2Π, B2Σ+, C2Πand D2Σ+ states of the CaBr and CaI radicals

The lifetimes of the A2Π, B2Σ+, C2Π and D2Σ+ states of the CaBr and CaI radicals have been measured directly from the time rate of fluorescence decay using an appropriate pulsed dye laser as an excitation source. The zero pressure radiative lifetimes determined for the first time for the C2Π1/2 state of CaI and D2Σ+ state of CaBr were (50.5 ± 1.5) ns and (21.0 ± 2.6) ns, respectively. The measured lifetimes agree well with trends predicted by a Ligand Field (L-F) model. For the CaI C2Π3/2 state (τ = 31.2 ns at 1 mbar pressure) and D2Σ+ state (τ < 11 ns), anomalously short lifetimes are observed, indicating that these states are predissociated.