Extension of the millimeter- and submillimeter-wave spectral databases of deuterated methyl cyanides (CH₂DCN and CHD₂CN)

Abstract

Context. The study of deuterated abundant molecules is recognized as important in understanding molecular complexity in starforming regions. Aims. We seek to assign the laboratory millimeter and submillimeter wave rotational spectra of the CHD 2 CN and CH 2 DCN deuterated isotopologues of methyl cyanide over a wide frequency range in order to provide precise spectral predictions for observations. Methods. Using the solid-state submillimeter-wave spectrometer in Lille, we measured and assigned 723 new lines for CHD 2 CN and 307 new lines for CH 2 DCN. The observed rotational transition frequencies were fitted with the ASFIT program to determine the spectroscopic parameters. The prediction of transition frequencies was performed using the SPCAT program. Results. Measurements for both isotoplogues were taken up to 945 GHz and are made available at the CDS. For CHD 2 CN this is significantly higher than the previous range of measurement up to 40 GHz. For CH 2 DCN many more lines of high K a have been measured than previously. Conclusions. Our work confirms the recent analysis for CHD 2 CN given in the CDMS database and extends the number of determined molecular parameters from 10 to 19. For CH 2 DCN, 3 new parameters including D K have been determined, and the uncertainty on parameters has been decreased by a factor of approximately 2. For both isotopologues the measured data show shifts in the frequency of some high K a transitions that are attributed to interactions with a low-lying vibrational state. The availability of more directly measured data and the increase in confidence of the predictions to higher quantum numbers and frequencies will be helpful for the radio astronomical detection of deuterated isotopologues of methyl cyanide in the interstellar medium.

Halogen bonding properties of 4-iodopyrazole and 4-bromopyrazole explored by rotational spectroscopy and ab initio calculations

“…60 Figure 3 shows the spectra recorded in both regions after removal of peaks corresponding to the fragments listed above. Spectra subsequently recorded for the N-deuterated isotopologue (510k and 280k FIDs for the 2.0-8.0 GHz and 7.0-18.5 GHz frequency ranges, respectively) revealed transitions of deuterated species including CH 2 DCN, 61,62 CHD 2 CN, 62,63 66 and CD 2 (CN) 2 . 66 Consistent with the relative magnitudes of the aand bcomponents of the dipole moment (calculated to be 0.80 D and 2.18 D, respectively), the observed spectra of both 4iodopyrazole and its N-deuterated isotopologue consist primarily of b-type transitions with some a-type transitions also observed.…”

Millimeter and submillimeter wave spectra of mono-13C-acetaldehydes

“…This paper is a continuation of a series of studies conducted in PhLAM Lille (France) that are devoted to the investigations of the spectra of different isotopic species of astrophysical molecules (Demyk et al 2007;Margulès et al 2009aMargulès et al ,b, 2010Carvajal et al 2009;Tercero et al 2012;Bouchez et al 2012;Coudert et al 2012Coudert et al , 2013Richard et al 2012Richard et al , 2013Haykal et al 2013;Kutsenko et al 2013;Nguyen et al 2013). In particular, these works led to the first interstellar detection of HCOOCH 2 D (Coudert et al 2013), HCOO 13 CH 3 (Carvajal et al 2009), HCO 18 OCH 3 , HC 18 OOCH 3 (Tercero et al 2012), and CH 2 DOCH 3 (Richard et al 2013).…”

Conformational isomers oftrans-urocanic acid observed by rotational spectroscopy

“…GHz region was averaged over 2.13 million FIDs and several new features were observed. Some of these readily assign to deuterated fragmentation products, specifically DC3N, 45 CH2DCN, 46,47 and CHD2CN. 47,48 It will be shown that other transitions assign to the spectra of deuterated isotopologues of conformers of trans-UCA.…”

“…Some of these readily assign to deuterated fragmentation products, specifically DC3N, 45 CH2DCN, 46,47 and CHD2CN. 47,48 It will be shown that other transitions assign to the spectra of deuterated isotopologues of conformers of trans-UCA. Spectra were carefully surveyed for evidence of transitions of cis-UCA, which differs from trans-UCA in respect of the steric configuration at the C(7) atom, but no evidence of this isomer was identified.…”