High-resolution laser excitation spectroscopy of the A ~2E-X~2/A_1 transition of SrCH_3

摘要

High-resolution laser excitation spectroscopy has been used to record the A ~2E-X ~2A,electronic transition of SrCH_3 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 ~2E and ~2A_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 ~2E state were determined.A comparison of the spin-orbit energy separation in the A E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible.The spin-rotation constants for the A ~2E 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 ~2E state of SrCH_3 is not entirely of p orbital character.The rotational constants were used to estimate the structural parameters of SrCH_3 in the A ~2E state.The strontium-carbon bond length was found to decrease by approx 0.006 A,and the hydrogen-carbon-hydrogen bond angle opened by approx 0.8 deg compared to the X~2A_1 state,similar to the geometry changes observed for CaCH_3.