The ν4 (SiF3 degenerate stretch) fundamental band of SiHF3 has been investigated by the CO2 laser Stark spectroscopy. The vibrationally induced dipole moment was found to give remarkable perturbations of the type (Δl,ΔK) = (2, - 1) in the ν4 vibrational state under intense electric field. Several perturbation-induced rovibrational transitions obeying the Δ(K - l) = ±3 selection rules were observed in the Stark spectrum. The C0 rotational constant, which is otherwise hard to obtain for a symmetric top molecule, was determined to be 4134.73(71) MHz. The vibrationally induced dipole moment μ, in the ν4 state was derived as ±0.034 38(17) D, the sign being experimentally indeterminable. The band origin, the Coriolis constant Cζ4, and the vibration-rotation constant α4care 999.581 076(30) cm-1, 2445.59(71) MHz, and 9.243(22) MHz, respectively. The dipole moment is 1.359 20(22) D in the ground state, and increases by 0.026 73(10) D on excitation of the ν4 vibration. The uncertainties given in the parentheses correspond to three standard deviations. The present results are compared with our previous results of a similar analysis for the deuterated species. The dipole moment in the ground vibrational state decreases by 0.002 01(28) D on deuteration. The vibrationally induced dipole moments μ, and the vibrational changes δμ4 of the dipole moment for both isotropic species are discussed theoretically. We introduce the coefficient of the mean square amplitude dependence for the bond moment, which is useful in the discussion.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry