THz extended spectrum of the monodeuterated methyl formate (DCOOCH₃)^⋆

¹ College of Physical Science and Technology, Central China Normal University, Luoyu Road 152, 430079 Wuhan PR China
² Departamento de Física Aplicada, Unidad Asociada CSIC, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva, Spain
e-mail: miguel.carvajal@dfa.uhu.es
³ Jet Propulsion Laboratory – NASA, California Institute of Technology, 4800, Oak Grove Drive, Pasadena, CA 91109-8099, USA
⁴ Laboratoire Interuniversitaire des Systèmes Atmosphériques, UMR CNRS 7583, Université Paris-Est Créteil et Université Paris Diderot, 61 Av. Charles de Gaulle, 94010 Créteil Cedex, France

Received: 13 November 2014
Accepted: 21 January 2015

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 DCOOCH₃ 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 DCOOCH₃ 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 CH₃ rotors.

Results. We fit 27 spectroscopic constants of DCOOCH₃ 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.