Millimeter- and submillimeter-wave spectrum of trans-formaldoxime (CH₂NOH)

Abstract

Context. Among the six atoms of N-containing molecules with the formula of CH 3 NO, only formamide (H 2 NCHO), the most stable structural isomer, has been detected in the interstellar medium (ISM). The formaldoxime isomer may be formed, for example, by the reaction of formaldehyde (H 2 CO) or methanimine (H 2 CNH) and hydroxylamine (H 2 NOH), which are all detected in the ISM. The lack of high accuracy millimeter-and submillimeter-wave measurements hinders the astronomical search for formaldoxime. Aims. The aim of this work is to provide the direct laboratory measurement of the millimeter-and submillimeter-wave spectrum of trans-formaldoxime. Methods. Formaldoxime was synthesized and its rotational spectrum was recorded at room temperature in a glass flow cell using the millimeter-and submillimeter-wave spectrometer in Lille. The SPFIT program in the CALPGM suite was used to fit the spectrum. Results. Rotational lines of trans-formaldoxime from both the ground state and v 12 = 1 vibrational excited states have been measured and assigned from 150 to 660 GHz. Spectroscopic constants were derived to the tenth order using both Watson's A and S reduction Hamiltonian.

The molecular structure and spectroscopic properties of formaldoxime (CH2NOH)

“…With the exception of D JK and h 3 , our calculation results are accord well with the experimental values at this theoretical level. The close agreement of D JK between our calculation and the results from Wu and Tan [16,19,20] can be found in table 9, however, there are significant differences between our results and those reported by Kaushik et al [43]. The relative error of D JK at B2PLYP/aug-cc-pVTZ theoretical level with the experimental value [20] is 4.34%, nevertheless, the corresponding relative error is 14.13% at the CCSD(T) theoretical level.…”

“…The close agreement of D JK between our calculation and the results from Wu and Tan [16,19,20] can be found in table 9, however, there are significant differences between our results and those reported by Kaushik et al [43]. The relative error of D JK at B2PLYP/aug-cc-pVTZ theoretical level with the experimental value [20] is 4.34%, nevertheless, the corresponding relative error is 14.13% at the CCSD(T) theoretical level. Besides, the relative error of h 3 between calculated and the experimental value [20] is approximately 14.59%, requiring further experiments to explain this phenomenon.…”

“…The value of A 0 (A e ) is much larger than B 0 (B e ) and C 0 (C e ), which plays a more important role in the rotational spectroscopic. For trans-formaldoxime, the calculation results are best matched with the experimental values [20], with relative errors of 0.53%, 0.06%, 0.02% at the CCSD(T)/aug-cc-pVTZ theoretical level, respectively. Furthermore, the CCSD(T) method, known for its high precision, is commonly used in calculating spectroscopic constants, which allows for more accurate results.…”

“…The relative error of D JK at B2PLYP/aug-cc-pVTZ theoretical level with the experimental value [20] is 4.34%, nevertheless, the corresponding relative error is 14.13% at the CCSD(T) theoretical level. Besides, the relative error of h 3 between calculated and the experimental value [20] is approximately 14.59%, requiring further experiments to explain this phenomenon. Due to the small magnitude of h 3 , its impact on molecular rotation is very small.…”

“…Recently, Zou et al measured and recorded the millimeter-and submillimeter-wave lines of trans-formaldoxime by direct absorption spectroscopy. On the one hand, accurate rotational lines of both the ground state and the vibrational excited state (ν 12 = 1) were detected in the range of 150-660 GHz; on the other hand, some spectroscopic constants were provided by DFT calculations [20].…”