Abstract

The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist in the detection of new species. Our goal consists in analyzing one of the two most stable species of the C3H4O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark clouds TMC-1 in the Taurus Molecular Cloud and Barnard 1 (B1-b). A millimeter-wave room-temperature rotational spectrum of methyl ketene was recorded from 50 to 330 GHz. The internal rotation analysis of its ground state and first torsional excited state was performed with the rho-axis method employing the RAM36 program. More than 3000 transitions of the rotational spectrum of the ground state (Kamax = 18) and first torsional excited state (Kamax = 13) of methyl ketene were fitted using a Hamiltonian that contains 41 parameters with an RMS (root mean square) of 41 kHz. Column density limits were calculated but no lines were detected in the ISM belonging to methyl ketene.

Highlights

  • A fundamental question in astrophysics and astrochemistry yet to be answered is to understand molecular complexity in space

  • The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules

  • Ketene (H2CCO), was detected a long time ago (Turner 1977) and provided that its isomer acrolein is likely to be present in the ISM, we investigate the rotational spectrum of methyl ketene in order to facilitate its detection in the ISM

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Summary

Introduction

A fundamental question in astrophysics and astrochemistry yet to be answered is to understand molecular complexity in space. After evaluating several groups of molecular isomers, Lattelais et al (2009, 2010, 2011) proposed the “minimum energy principle” (MEP) They stated that the thermodynamically most stable isomer of a molecular formula is practically the most abundant in the ISM. The latest rotational parameters for methyl ketene were published by Bak et al (1962, 1966) in the 1960s where they reported the analysis up to J = 3 and Ka = 2 in the 16–27 GHz frequency range. These values do not allow a precise extrapolation to the ISM observational frequency range. Ketene (H2CCO), was detected a long time ago (Turner 1977) and provided that its isomer acrolein is likely to be present in the ISM, we investigate the rotational spectrum of methyl ketene in order to facilitate its detection in the ISM

Computational calculations
Experiments
Analysis of the spectra
Radio-astronomical observations
Findings
Conclusion
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