High resolution IR study of the coriolis coupling between nu(3) and nu(9) in methylene chloride

The infrared spectra of the upsilon(3) and upsilon(9) bands of isotopically pure (CH2Cl2)-Cl-35 have been recorded at a resolution of 0.0025 cm(-1) in the range 600-800 cm(-1) with a Bruker IFS 120 HR Fourier Transform interferometer. The Coriolis coupling between the two CCl2 stretching fundamentals upsilon(3) and upsilon(9) has been investigated, An effective coupling constant xi(3,9)(c) = 0.20101(3) cm(-1) (zeta(3,9)(c) = 0.98) was obtained from a rotational analysis of spectra recorded at room temperature. From relative intensities the ratio of the vibrational transition moments of the fundamentals upsilon(3) and upsilon(9) could be estimated as