Broad-band high-resolution rotational spectroscopy for laboratory astrophysics^⋆

¹ Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/ Serrano 123, 28006 Madrid, Spain
e-mail: jose.cernicharo@csic.es
² Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
³ Instituto de Estructura de la Materia (IEM. CSIC), Molecular Physics Department, C/Serrano 123, 28006 Madrid, Spain
⁴ Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA., C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
⁵ IMDEA Nanociencia, Ciudad Universitaria de Cantoblanco, 28049 Cantoblanco, Madrid, Spain
⁶ IMDEA Materiales, C/Eric Kandel 2, Tecnogetafe, 28906 Getafe, Madrid, Spain
⁷ Centro de Investigaciones Químicas, UAEM. Av. Universidad, 1001 Col. Chamilpa, 62209 Cuernavaca, Morelos, Mexico
⁸ Centro de Astrobiología (CSIC-INTA), Crta. de Torrejón de Ardoz a Ajalvir km 4., Torrejón de Ardoz, 28850, Spain
⁹ Universidad de Cantabria, Department of Communication Engineering, Avda. Los Castros, 39005 Santander, Spain
¹⁰ Fraunhofer Institut fur Angewandte Festkorperphysik, Tullastresse 72, 79108 Freiburg, Germany

Received: 4 February 2019
Accepted: 14 March 2019

Abstract

We present a new experimental set-up devoted to the study of gas phase molecules and processes using broad-band high spectral resolution rotational spectroscopy. A reactor chamber is equipped with radio receivers similar to those used by radio astronomers to search for molecular emission in space. The whole range of the Q (31.5–50 GHz) and W bands (72–116.5 GHz) is available for rotational spectroscopy observations. The receivers are equipped with 16 × 2.5 GHz fast Fourier transform spectrometers with a spectral resolution of 38.14 kHz allowing the simultaneous observation of the complete Q band and one-third of the W band. The whole W band can be observed in three settings in which the Q band is always observed. Species such as CH₃CN, OCS, and SO₂ are detected, together with many of their isotopologues and vibrationally excited states, in very short observing times. The system permits automatic overnight observations, and integration times as long as 2.4 × 10⁵ s have been reached. The chamber is equipped with a radiofrequency source to produce cold plasmas, and with four ultraviolet lamps to study photochemical processes. Plasmas of CH₄, N₂, CH₃CN, NH₃, O₂, and H₂, among other species, have been generated and the molecular products easily identified by the rotational spectrum, and via mass spectrometry and optical spectroscopy. Finally, the rotational spectrum of the lowest energy conformer of CH₃CH₂NHCHO (N-ethylformamide), a molecule previously characterized in microwave rotational spectroscopy, has been measured up to 116.5 GHz, allowing the accurate determination of its rotational and distortion constants and its search in space.