High - resolution laser excitation spectroscopy of the à 2 E - X̃ 2 A 1 transition of

High-resolution laser excitation spectroscopy has been used to record the à E-X̃ A1 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 and A1 symmetric top Hamiltonian matrices in a Hund’s case a basis, using a least squares fitting program. Rotational and fine structure parameters for the à E state were determined. A comparison of the spin-orbit energy separation in the à E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the à E 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 à E state of SrCH3 is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH3 in the à E state. The strontium-carbon bond length was found to decrease by 0.006 Å, and the hydrogen-carbon-hydrogen bond angle opened by 0.8° compared to the X̃ A1 state, similar to the geometry changes observed for CaCH3. © 2006 American Institute of Physics. DOI: 10.1063/1.2189236