15min:
MILLIMETER AND SUBMILLIMETER WAVE SPECTRA OF THE HCOO13CH3 ISOTOPOLOG OF METHYLFORMATE IN THE GROUND STATE AND IN THE FIRST EXCITED TORSIONAL STATE..

I. HAYKAL, L. MARGULÈS, T. R. HUET, R. A. MOTIYENKO, Laboratoire PhLAM, UMR8523 CNRS-Université Lille 1, F-59655 Villeneuve d'Ascq Cedex, France; M. CARVAJAL, Unidad Asociada IEM-CSIC-Dpto. de Física Aplicada, Universidad de Huelva, Spain; I. KLEINER, LISA, CNRS et Université Paris Est et Paris Diderot, 61 av. Général de Gaulle, 94010, Créteil, France; J. C. GUILLEMIN, ENS de Chimie de Rennes -CNRS -35700 Rennes, France; B. TERCERO, J. CERNICHARO, Centro de Astrobiología (CSIC-INTA). Ctra de Ajalvir, Km 4, 28850 Torrejón de Ardoz, Madrid, Spain.

The detection of nineteen new rotational transitions of the parent molecule of methylformate (HCOOCH3) in the second lowest excited torsional mode ( nut =2) was recently reported in Orion-KL, as well as the detection of eighty new lines corresponding to the two 18O isotopologs of methylformate in their ground states. The laboratory work on HCOO13CH3 was continued. A wide spectral range from 50 to 940 GHz was recorded in Lille with the submillimeter-wave spectrometer based on harmonic generation of a microwave synthesizer source, using a multiplication chain of solid state sources (50-100 and 150-940 GHz) and a backward wave oscillator (100-150 GHz), and coupled to a 2.2 m cell. The absolute accuracy of the line positions is better than 30 kHz up to 630 GHz and 50 kHz above. The two states ( nut = 0 and 1) were fitted together using the RAM Hamiltonian of the BELGI program and a new set of 45 parameters was accurately determined. The fit contains 7050 lines corresponding to the ground state up to J = 78 and Ka = 34 and 1907 lines related to nut =1 up to J = 59 and Ka = 24. The detection of new nut =1 lines in Orion KL will be reported and discussed.

This work is supported by the French Programme National de Physico-Chimie du Milieu Interstellaire (CNRS), by CNES, and by the Spanish Government through the grants FIS2011-28738-C02-02 and CONSOLIDER 2009-00038.