High-resolution Fourier transform infrared (FTIR) spectroscopy of formaldoxime-13C (13CH2NOH): Ground and [formula omitted] states rovibrational constants

Abstract

The high-resolution Fourier transform infrared (FTIR) spectrum of formaldoxime-13C (13CH2NOH) was recorded in the 840–930 cm−1 region with an unapodized resolution of 0.0019 cm−1 for a rovibrational analysis. In the analysis of the dominantly A-type ν8 band, a total of 1025 infrared transitions were fitted using the Watson's A-reduced and S-reduced Hamiltonians in the Ir representation with a root-mean-square (rms) deviations of 0.000430 cm−1 and 0.000431 cm−1 respectively. From the rovibrational analysis, the ν8 = 1 states rotational constants (A, B and C), five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) and one sextic term (ΦKJ) were derived for the first time. The band center of the ν8 band of 13CH2NOH was found to be 890.235170(25) cm−1 and 890.235182(25) cm−1 in the A-reduced and S-reduced Hamiltonians respectively. Ground state rovibrational constants except for rotational constants B and C were obtained for the first time through the fitting of 443 ground state combination differences (GSCDs) derived from the infrared transitions of the ν8 band of 13CH2NOH, together with 2 previously reported microwave frequencies. The rms deviation of the GSCD fits was the same at 0.000430 cm−1 for both A-reduced and S-reduced Hamiltonians. Furthermore, rovibrational constants up to 5 quartic centrifugal distortion terms of the ground state, and the band center and rotational constants (A, B and C) of the ν8 = 1 state were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set. Good agreement was found between the experimental and calculated rovibrational constants of 13CH2NOH for both ground and ν8 = 1 states.