On the improvement of the rotational structure analysis of ¹³CH₃D ground vibrational state

Abstract

The main goal of the present study was to improve the already published rotational structure analysis of the ground vibrational state of the ¹³CH₃D molecule. To realise that, we recorded high-resolution spectra of a set of the strongly interacting vibrational bands, 2ν₃(A ₁), 2ν₆(A ₁), 2ν₆(E), ν₂(A ₁), ν₅ + ν₆(A ₁), ν₅ + ν₆(A ₂), ν₅ + ν₆(E) and ν₃ + ν₆(E). From the analysis of the experimental data, more than 1900 ground state combination differences (GSCD) were determined with , and . The a ₁/a ₂ splittings of the states with quantum number K = 3 were taken into account. The presence of numerous forbidden transitions allowed us to determine with high accuracy GSCD not only with ΔK = 0, but with ΔK = ±1, ±2 and ±3, as well. Spectroscopic parameters of the ground vibrational state were determined from the joint fit of the obtained GSCD (they are reproduced with cm⁻¹). The 21 highly accurate THz-region transitions which were also used as input data, are reproduced with kHz.

Keywords:

• monodeuterated methane
• ground state rotational structure
• spectroscopic parameters

Notes

^aExperimental values reproduced from Ref. [30].

^bDifferences between values of experimental transitions and corresponding values calculated with the obtained set of spectroscopic parameters from column 2 of Table 2.

^cValues of differences reproduced from Ref. [30].

^dDoublet should be here in accordance with the theory. The lines were not experimentally resolved in Ref. [30].

^aValues in parentheses are one standard deviation given in units of the last digit. Values that are presented without standard deviation have been fixed to the values from Ref. [28].