High resolution spectroscopic study of CH3D in the region 5900–6100 cm−1

Abstract

The vibrational overtone band of monodeuterated methane (CH3 in the region 5900–6100 cm−1 was recorded by a high resolution Fourier transform spectrometer. Rotational analyses were performed separately for the parallel 2v 4(A1) and perpendicular 2v 4(E) bands, whose origins were found to be 5980.41 cm−1 and 6022.21 cm−1, respectively. The A1 band displays J-resolved rotational structure while the K structure is resolved only at higher J values. A resonance Hamiltonian with the polyad number P = 2n 1 + 2n 4 + n 5 is derived using the fourth order Canonical Van Vleck Perturbation Theory (CVPT) to show that the 2v 4(A1 and 2v 4(E) are vibrationally perturbed by Fermi and Darling—Dennison resonances. The observation of rotational l-resonance in the 2v 4(E) band is a consequence and evidence of the mixing of the vibrational states with different l values.