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Title: Desorption Kinetics and Binding Energies of Small Hydrocarbons

Abstract

Small hydrocarbons are a vital organic reservoir in protostellar and protoplanetary environments. Constraints on desorption temperatures and binding energies of such hydrocarbons are essential for accurate predictions of where these molecules exist in the ice versus gas phase during the different stages of star and planet formation. Here, 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 onmore » sublimation front locations (i.e., snowlines) in protoplanetary disks.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4];  [4];  [4];  [4]; ORCiD logo [4]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1545285
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 875; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
astrochemistry; methods: laboratory: molecular; protoplanetary disks

Citation Formats

Behmard, Aida, Fayolle, Edith C., Graninger, Dawn M., Bergner, Jennifer B., Martín-Doménech, Rafael, Maksyutenko, Pavlo, Rajappan, Mahesh, and Öberg, Karin I. Desorption Kinetics and Binding Energies of Small Hydrocarbons. United States: N. p., 2019. Web. doi:10.3847/1538-4357/ab0e7b.
Behmard, Aida, Fayolle, Edith C., Graninger, Dawn M., Bergner, Jennifer B., Martín-Doménech, Rafael, Maksyutenko, Pavlo, Rajappan, Mahesh, & Öberg, Karin I. Desorption Kinetics and Binding Energies of Small Hydrocarbons. United States. doi:10.3847/1538-4357/ab0e7b.
Behmard, Aida, Fayolle, Edith C., Graninger, Dawn M., Bergner, Jennifer B., Martín-Doménech, Rafael, Maksyutenko, Pavlo, Rajappan, Mahesh, and Öberg, Karin I. Wed . "Desorption Kinetics and Binding Energies of Small Hydrocarbons". United States. doi:10.3847/1538-4357/ab0e7b.
@article{osti_1545285,
title = {Desorption Kinetics and Binding Energies of Small Hydrocarbons},
author = {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.},
abstractNote = {Small hydrocarbons are a vital organic reservoir in protostellar and protoplanetary environments. Constraints on desorption temperatures and binding energies of such hydrocarbons are essential for accurate predictions of where these molecules exist in the ice versus gas phase during the different stages of star and planet formation. Here, through a series of temperature programmed desorption experiments, we constrain the binding energies of 2- and 3-carbon hydrocarbons (C2H2—acetylene, C2H4—ethylene, C2H6—ethane, C3H4—propyne, C3H6—propene, and C3H8—propane) to 2200–4200 K in the case of pure amorphous ices, to 2400–4400 K on compact amorphous H2O, and to 2800–4700 K on porous amorphous H2O. 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 N2. Thus in the case of hydrocarbons, H2O has a less pronounced effect on sublimation front locations (i.e., snowlines) in protoplanetary disks.},
doi = {10.3847/1538-4357/ab0e7b},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 875,
place = {United States},
year = {2019},
month = {4}
}

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This content will become publicly available on April 17, 2020
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