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Desorption Kinetics and Binding Energies of Small Hydrocarbons

Behmard, Aida and Fayolle, Edith C. and Graninger, Dawn M. and Bergner, Jennifer B. and Martín-Doménech, Rafael and Maksyutenko, Pavlo and Rajappan, Mahesh and Öberg, Karin I. (2019) Desorption Kinetics and Binding Energies of Small Hydrocarbons. Astrophysical Journal, 875 (1). Art. No. 73. ISSN 1538-4357. doi:10.3847/1538-4357/ab0e7b.

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Small hydrocarbons are an important organic reservoir in protostellar and protoplanetary environments. Constraints on desorption temperatures and binding energies of such hydrocarbons are needed for accurate predictions of where these molecules exist in the ice versus gas phase during the different stages of star and planet formation. Through a series of temperature programmed desorption experiments, we constrain the binding energies of 2- and 3-carbon hydrocarbons (C_2H_2—acetylene, C_2H_4—ethylene, C_2H_6—ethane, C_3H_4—propyne, C_3H_6—propene, and C_3H_8—propane) to 2200–4200 K in the case of pure amorphous ices, to 2400–4400 K on compact amorphous H_2O, and to 2800–4700 K on porous amorphous H_2O. The 3-carbon hydrocarbon binding energies are always larger than the 2-carbon hydrocarbon binding energies. Within the 2- and 3-carbon hydrocarbon families, the alkynes (i.e., least-saturated) hydrocarbons exhibit the largest binding energies, while the alkane and alkene binding energies are comparable. Binding energies are ~5%–20% higher on water ice substrates compared to pure ices, which is a small increase compared to what has been measured for other volatile molecules such as CO and N_2. Thus in the case of hydrocarbons, H_2O has a less pronounced effect on sublimation front locations (i.e., snowlines) in protoplanetary disks.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Behmard, Aida0000-0003-0012-9093
Fayolle, Edith C.0000-0001-8109-5256
Graninger, Dawn M.0000-0003-1582-0581
Bergner, Jennifer B.0000-0002-8716-0482
Öberg, Karin I.0000-0001-8798-1347
Additional Information:© 2019 The American Astronomical Society. Received 2018 August 29; revised 2019 March 6; accepted 2019 March 8; published 2019 April 17. A.B. acknowledges funding from the Origins of Life Initiative at Harvard. E.C.F.'s contribution was partly carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. K.I.Ö. acknowledges funding from the Simons Collaboration on the Origins of Life Investigator award #321183.
Funding AgencyGrant Number
Harvard UniversityUNSPECIFIED
Simons Foundation321183
Subject Keywords:astrochemistry – methods: laboratory: molecular – protoplanetary disks
Issue or Number:1
Record Number:CaltechAUTHORS:20190417-154104665
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Official Citation:Aida Behmard et al 2019 ApJ 875 73
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94764
Deposited By: Tony Diaz
Deposited On:17 Apr 2019 22:58
Last Modified:16 Nov 2021 17:07

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