MILLIMETRE-WAVE SPECTRUM OF ISOTOPOLOGUES OF ETHANOL FOR RADIO-ASTRONOMY Adam Walters, IRAP, Université de Toulouse, UPS-OMP-CNRS, France. Mirko Schäfer, Matthias H. Ordu, Frank Lewen, Stephan Schlemmer, Holger S.P. Müller, I. Physikalisches Institut, Universität zu Köln, Germany.

Molecular complexity in space Star-forming regionsComets & meteorites iso-propyl cyanide, methyl acetate, ethyl formate, acetamide, glycoaldehyde,aminoacetonitrile ethanol, … amino acids ? NASA / ESA Basilicofresco

Abundance Partition function ➡ Need accurate predictions over a large frequency range from laboratory spectroscopy. Use sensitive spectrometers & long pass cells. Difficulties in studying isotopologues of complex molecules in the ISM

Ethanol observed in star-forming regions and hot-cores Ethanol thought to be formed on grains and to be involved in formation of more complex species More and more broad astrophysical spectral surveys available – move towards analysing spectra as a whole – need information on all species present Work on D-ethanol complementary to previous on 13 C ethanol Over-abundance of deuterated complex molecules in star-forming regions Study of isotopologues could give information on formation routes Interest in studying ethanol

Ethanol observed extensively in star-forming regions and hot-cores Interest – multi species analysis

Interest - ALMA Lobe IRAM 30m 180 GHz (14’’) 250 GHz (10’’) Lobe ALMA ALMA Band 6 (230 GHz) (~2’’, baseline = 160m) 66 radio telescopes high sensitivity high spatial resolution ESO

7 Background - Formation Formation mechanism of ethanol in the ISM not conclusively known Possible formation routes : - In the gas phase (e.g. Millar et al. 1991): H 3 O + + C 2 H 4 → C 2 H 5 OH hν C 2 H 5 OH e - → C 2 H 5 OH + H - From dissociated carbons as proposed for grain-surface reaction (Bernstein et al. 1995): CH 3 + CH 2 O → CH 3 CH 2 O CH 3 CH 2 O + H→ CH 3 CH 2 OH

Background - Ethanol Prolate slightly asymmetric top with two large amplitude internal motions: Hydroxyl group. Two conformations in the groundstate: gauche (+ and -) and anti. Methyl group. Internal rotation J.C. Pearson et al. J. Phys. Chem. (1995), J Mol Spectrosc, 251 (2008) Asymmetric rotor level J, K a, K c Anti Gauche + Gauche - 3,27 cm -1 39,49 cm -1 V=0

Background -Deuterated Ethanol CH 2 DCH 3 OH (s- and a-) CH 3 CHDOH CH 3 CH 2 OD

10 Background – dataset Dataset chosen for first astrophysical identification. Anti- conformer (lowest energy) Torsional ground state Torsional splitting unlikely to be resolved in astrophysical spectra b-type spectra

Previous measurements  references are given in our publication (see last slide)

Experimental setup Double-pass cell Solid-state sources Computer control Highly user friendly These measurements: 35 − 500 GHz

Results – onset of shifts Dataset chosen for first astrophysical detection. First analysis with standard S-reduction Watson Hamiltonian and without considering torsion-rotation and anti-gauche interactions. (SPFIT, SPCAT – H.M. Pickett)

Results – example scan

Results – parameter list

Deutsche Forschungsgemeinschaft (DFG) - collaborative research grant SFB 956 CNRS – Programme PCMI France : Programme National de Physique et Chimie du Milieu Interstellaire Acknowledgements 13 C-ethanol  Bouchez et al, Journal of Quantitative Spectroscopy & Radiative Transfer 113 (2012) 1148–1154 D-ethanol  Walters et al, Journal of Molecular Spectroscopy 314 (2015) 6-12 References