Astron. Astrophys. 331, 749-759 (1998)

Constraints on the abundances of various molecules in interstellar ice:
laboratory studies and astrophysical implications

Nathalie Boudin ^{1, 2}, Willem A. Schutte ¹ and J. Mayo Greenberg <sup>1

1</sup> Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
² Ecole Nationale Supérieure de Chimie et de Physique de Bordeaux, Avenue Pey Berland, B.P. 108, F-33402 Talence Cedex, France

Received 19 August 1997 / Accepted 31 October 1997

Abstract

Ethane, acetylene, ethanol, hydrazine and hydrogen peroxyde are either predicted by theoretical models to be abundant in the icy mantles on grains in dense clouds, or were found to be produced by comets. We present measurements of the spectra of these species embedded in astrophysically relevant ice matrices. Additionally, we obtained the spectrum of the hydrozonium ion () which could be produced by activationless acid-base reactions. The laboratory results are compared to the ISO and ground-based spectra of NGC 7538:IRS 9. Strict upper-limits compared to the solid water could be found for ethane, ethanol and hydrogen peroxyde of %, %, and %, respectively. These results give some important information on the relationship between cometary and interstellar ices and on the nature of grain surface reactions.

Key words: methods: laboratory stars: individual: NGC 7538:IRS 9 ISM: molecules ISM: abundances infrared: ISM: lines and bands

Send offprint requests to: W.A. Schutte

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Contents

• 1. Introduction
• 2. Experimental
• 3. Results
  • 3.1. Ethane: C₂ H₆
  • 3.2. Acetylene: C₂ H₂
  • 3.3. Ethanol: CH₃ CH₂ OH
  • 3.4. Hydrogen peroxide: H₂ O₂
  • 3.5. Hydrazine: N₂ H₄
  • 3.6. Hydrozonium ion:
• 4. Comparison to observations
• 5. Astrophysical implications
• 6. Conclusion
• Acknowledgements
• Appendix A: behaviour during warm-up
• References

© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998
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