THz extended spectrum of the monodeuterated methyl formate (DCOOCH₃)

Abstract

Context. Laboratory spectral recordings and an accurate molecular spectral analysis of any potential interstellar molecule are essential for generating a complete spectroscopic line list. This permits predicting the frequencies and intensities of any transition so that subsequently, it can be identified in the interstellar medium. Aims. Our analysis of DCOOCH 3 aims to provide a comprehensive spectral catalog that encompasses as much as possible the frequency coverage of the new-generation far-IR and submillimeter wave observation facilities. Methods. We newly measured the rotational spectrum of DCOOCH 3 in the laboratory of the Jet Propulsion Laboratory in the frequency range of 0.85 to 1.5 THz. We jointly analyzed the new data with literature data using the rho axis method, which is a tool developed for the spectral analysis of molecules with large-amplitude internal CH 3 rotors. Results. We fit 27 spectroscopic constants of DCOOCH 3 to 3763 transitions with highest values of J = 69 and K a = 36 of the ground torsional state with a standard (unitless) deviation of 0.97. With respect to previous work, this is a significantly better result that was obtained with 2060 more transitions, and we also achieved a better accuracy for the new parameter values.

The Borderline between Reactivity and Pre‐reactivity of Binary Mixtures of Gaseous Carboxylic Acids and Alcohols

“…Therotational spectra of methylformate and ethyl formate are available. [13,14] In all cases the rotational transitions of the monomers (acid and alcohol) were present in the spectra. Their intensities decreased considerably,h owever,w hen we observed the ester.…”

Rotational spectroscopic study of S-methyl thioformate

“…In the present work, we used the BELGI-Cs 1 program ( Hougen et al 1994 ) using the rho-axis method (RAM) with a two-step procedure initially described by Herbst et al (1984 ). The BELGI-C s code was previously applied successfully to a number of interstellar molecules containing an internal methyl rotor and was used in particular for the parent species of the cis- methyl formate ( Carvajal et al 2007 ) as well as for its 13 C isotopic species H 13 COOCH 3 and HCOO 13 CH 3 ( Carvajal et al 2009 ), 18 O isotopologues HC 18 OOCH3 and HCO 18 OCH3 ( Tercero et al 2012 ), and deuterated species DCOOCH3 ( Duan et al 2015 ). The method takes its name from the choice of the axis system, which allows us to minimize the coupling between internal rotation and global rotation in the Hamiltonian, at least in the zeroth order.…”

“…For calculations of the line strengths, we used the same procedure as the one described in detail in Section 3.2 of (Kleiner 2010). This method had been used for different molecules with C s symmetry containing one methyl rotor such as methyl formate and its isotopologues (Favre et al 2014;Carvajal et al 2009;Haykal et al 2014;Carvajal et al 2007;Tercero et al 2012;Duan et al 2015) or vinyl acetate (Kolesnikova et al 2015). We used the BELGI-C s code to calculate the line strengths, using the energy parameters determined in Table 2.…”

The Borderline between Reactivity and Pre‐reactivity of Binary Mixtures of Gaseous Carboxylic Acids and Alcohols

“…As usually happens, we observed some unassigned lines (in the broadband spectra there are even more unassigned lines due to spurious signals), but they do not have patterns which can match the expected spectra. The rotational spectra of methylformate and ethyl formate are available …”