High-resolution laser excitation spectroscopy of the (A)over-tilde2E- (X)over-tilde2A1 transition of SrCH3

High-resolution laser excitation spectroscopy has been used to record the A E-2-X (2)A(1) electronic transition of SrCH3 in a laser ablation/molecular jet source. Transitions arising from the K-'=1 <- K-'=0, K-'=0 <- K-'=1, and K-'=2 <- K-'=1 subbands have been observed and assigned. The data were modeled with E-2 and (2)A(1) symmetric top Hamiltonian matrices in a Hund's case (a) basis, using a least squares fitting program. Rotational and fine structure parameters for the A E-2 state were determined. A comparison of the spin-orbit energy separation in the A E-2 state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the A E-2 state were calculated using the pure precession model and were found to be in good agreement with the experimentally determined parameters. These calculations suggest that the A E-2 state of SrCH3 is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH3 in the A E-2 state. The strontium-carbon bond length was found to decrease by similar to 0.006 A, and the hydrogen-carbon-hydrogen bond angle opened by similar to 0.8 degrees compared to the X (2)A(1) state, similar to the geometry changes observed for CaCH3. (c) 2006 American Institute of Physics.