Fourier transform infrared (FTIR) spectroscopy of formaldoxime isotopologue 12CD2NOH in the 300–3700 cm−1 region and its ν12 and ν9 bands: Vibrational and rovibrational analyses

Abstract

The Fourier transform infrared (FTIR) spectrum of the formaldoxime isotopologue 12CD2NOH was recorded in the 500–3700 cm−1 region with a resolution of 0.50 cm−1 to identify its fundamental, overtone and combination bands and to measure their relative infrared (IR) band intensities. Furthermore, the high-resolution (0.00096 cm−1) FTIR spectrum of ν12 and ν9 bands of 12CD2NOH was recorded in Australian Synchrotron in the 300–510 cm−1 region for a rovibrational analysis. A total of 1060 IR transitions of the C-type ν12 band were fitted using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.000524 cm−1. From the rovibrational analysis, the v12 = 1 state rovibrational constants up to all 5 quartic centrifugal distortion terms were derived for the first time. The band center of the ν12 band of 12CD2NOH was found to be 391.214740(46) cm−1. The ground state rovibrational constants up to all 5 quartic terms were determined for the first time by the fitting of 423 ground state combination differences (GSCDs) derived from the IR transitions of the ν12 band of 12CD2NOH of this work. The rms deviation of the GSCD fit was 0.000473 cm−1 using the Watson’s A-reduced Hamiltonian in the Ir representation. Furthermore, a total of 724 IR transitions of the predominantly B-type ν9 band of 12CD2NOH were fitted with a rms deviation of 0.000360 cm−1 to derive the band center at 465.151277(39) cm−1 and rovibrational constants of the v9 = 1 state up to 4 quartic terms for the first time. Additionally, all 3 rotational constants and 5 quartic centrifugal distortion terms of the ground state and 3 rotational constants of the v12 = 1 and v9 = 1 states of 12CD2NOH were computed from theoretical anharmonic calculations at 2 different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. Close agreement was found for the calculated and experimental rotational constants of 12CD2NOH for the ground, v12 = 1 and v9 = 1 states. The vibrational frequencies (cm−1) of 12 fundamental bands of 12CD2NOH in the 300–3700 cm−1 region, and their IR band intensities (km/mol) were also calculated using B3LYP and MP2 with the cc-pVTZ basis set, and they were compared with the respective experimental data.