Desorption rates and sticking coefficients for CO and N2 interstellar ices

S.E. Bisschop, H.J. Fraser, K.I. Öberg, E.F. van Dishoeck, S. Schlemmer

Research output: Contribution to journalArticle

131 Citations (Scopus)

Abstract

We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered and mixed morphologies at various ice "thicknesses" and abundance ratios as well as simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the binding energies of CO and N2 in both pure and mixed environments and to derive the kinetics for desorption, mixing and segregation. For mixed ices N2 desorption occurs in a single step whereas for layered ices it proceeds in two steps, one corresponding to N2 desorption from a pure N2 ice environment and one corresponding to desorption from a mixed ice environment. The latter is dominant for astrophysically relevant ice "thicknesses". The ratio of the binding energies, R_BE, for pure N2 and CO is found to be 0.936 ± 0.03, and to be close to 1 for mixed ice fractions. The model is applied to astrophysically relevant conditions for cold pre-stellar cores and for protostars which start to heat their surroundings. The importance of treating CO desorption with zeroth rather than first order kinetics is shown. The experiments also provide lower limits of 0.87 ± 0.05 for the sticking probabilities of CO-CO, N2-CO and N2-N2 ices at 14 K. The combined results from the desorption experiments, the kinetic model, and the sticking probability data lead to the conclusion that these solid-state processes of CO and N2 are very similar under astrophysically relevant conditions. This conclusion affects the explanations for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and protostellar cores.
LanguageEnglish
Pages1297-1309
Number of pages13
JournalAstronomy and Astrophysics
Volume449
Issue number3
DOIs
Publication statusPublished - Apr 2006

Fingerprint

desorption
ice
coefficients
ice environments
stellar cores
kinetics
ice thickness
binding energy
protostars
experiment
rate
energy
infrared spectra
solid state
absorption spectra
heat
temperature

Keywords

  • interstellar ices
  • pre-stellar
  • protostellar
  • astrophysics
  • desorption experiments

Cite this

Bisschop, S. E., Fraser, H. J., Öberg, K. I., van Dishoeck, E. F., & Schlemmer, S. (2006). Desorption rates and sticking coefficients for CO and N2 interstellar ices. Astronomy and Astrophysics, 449(3), 1297-1309. https://doi.org/10.1051/0004-6361:20054051
Bisschop, S.E. ; Fraser, H.J. ; Öberg, K.I. ; van Dishoeck, E.F. ; Schlemmer, S. / Desorption rates and sticking coefficients for CO and N2 interstellar ices. In: Astronomy and Astrophysics. 2006 ; Vol. 449, No. 3. pp. 1297-1309.
@article{d9e61e80a16641cc8b2153dce5397523,
title = "Desorption rates and sticking coefficients for CO and N2 interstellar ices",
abstract = "We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered and mixed morphologies at various ice {"}thicknesses{"} and abundance ratios as well as simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the binding energies of CO and N2 in both pure and mixed environments and to derive the kinetics for desorption, mixing and segregation. For mixed ices N2 desorption occurs in a single step whereas for layered ices it proceeds in two steps, one corresponding to N2 desorption from a pure N2 ice environment and one corresponding to desorption from a mixed ice environment. The latter is dominant for astrophysically relevant ice {"}thicknesses{"}. The ratio of the binding energies, R_BE, for pure N2 and CO is found to be 0.936 ± 0.03, and to be close to 1 for mixed ice fractions. The model is applied to astrophysically relevant conditions for cold pre-stellar cores and for protostars which start to heat their surroundings. The importance of treating CO desorption with zeroth rather than first order kinetics is shown. The experiments also provide lower limits of 0.87 ± 0.05 for the sticking probabilities of CO-CO, N2-CO and N2-N2 ices at 14 K. The combined results from the desorption experiments, the kinetic model, and the sticking probability data lead to the conclusion that these solid-state processes of CO and N2 are very similar under astrophysically relevant conditions. This conclusion affects the explanations for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and protostellar cores.",
keywords = "interstellar ices, pre-stellar, protostellar, astrophysics, desorption experiments",
author = "S.E. Bisschop and H.J. Fraser and K.I. {\"O}berg and {van Dishoeck}, E.F. and S. Schlemmer",
year = "2006",
month = "4",
doi = "10.1051/0004-6361:20054051",
language = "English",
volume = "449",
pages = "1297--1309",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "3",

}

Bisschop, SE, Fraser, HJ, Öberg, KI, van Dishoeck, EF & Schlemmer, S 2006, 'Desorption rates and sticking coefficients for CO and N2 interstellar ices' Astronomy and Astrophysics, vol. 449, no. 3, pp. 1297-1309. https://doi.org/10.1051/0004-6361:20054051

Desorption rates and sticking coefficients for CO and N2 interstellar ices. / Bisschop, S.E.; Fraser, H.J.; Öberg, K.I.; van Dishoeck, E.F.; Schlemmer, S.

In: Astronomy and Astrophysics, Vol. 449, No. 3, 04.2006, p. 1297-1309.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Desorption rates and sticking coefficients for CO and N2 interstellar ices

AU - Bisschop, S.E.

AU - Fraser, H.J.

AU - Öberg, K.I.

AU - van Dishoeck, E.F.

AU - Schlemmer, S.

PY - 2006/4

Y1 - 2006/4

N2 - We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered and mixed morphologies at various ice "thicknesses" and abundance ratios as well as simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the binding energies of CO and N2 in both pure and mixed environments and to derive the kinetics for desorption, mixing and segregation. For mixed ices N2 desorption occurs in a single step whereas for layered ices it proceeds in two steps, one corresponding to N2 desorption from a pure N2 ice environment and one corresponding to desorption from a mixed ice environment. The latter is dominant for astrophysically relevant ice "thicknesses". The ratio of the binding energies, R_BE, for pure N2 and CO is found to be 0.936 ± 0.03, and to be close to 1 for mixed ice fractions. The model is applied to astrophysically relevant conditions for cold pre-stellar cores and for protostars which start to heat their surroundings. The importance of treating CO desorption with zeroth rather than first order kinetics is shown. The experiments also provide lower limits of 0.87 ± 0.05 for the sticking probabilities of CO-CO, N2-CO and N2-N2 ices at 14 K. The combined results from the desorption experiments, the kinetic model, and the sticking probability data lead to the conclusion that these solid-state processes of CO and N2 are very similar under astrophysically relevant conditions. This conclusion affects the explanations for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and protostellar cores.

AB - We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered and mixed morphologies at various ice "thicknesses" and abundance ratios as well as simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the binding energies of CO and N2 in both pure and mixed environments and to derive the kinetics for desorption, mixing and segregation. For mixed ices N2 desorption occurs in a single step whereas for layered ices it proceeds in two steps, one corresponding to N2 desorption from a pure N2 ice environment and one corresponding to desorption from a mixed ice environment. The latter is dominant for astrophysically relevant ice "thicknesses". The ratio of the binding energies, R_BE, for pure N2 and CO is found to be 0.936 ± 0.03, and to be close to 1 for mixed ice fractions. The model is applied to astrophysically relevant conditions for cold pre-stellar cores and for protostars which start to heat their surroundings. The importance of treating CO desorption with zeroth rather than first order kinetics is shown. The experiments also provide lower limits of 0.87 ± 0.05 for the sticking probabilities of CO-CO, N2-CO and N2-N2 ices at 14 K. The combined results from the desorption experiments, the kinetic model, and the sticking probability data lead to the conclusion that these solid-state processes of CO and N2 are very similar under astrophysically relevant conditions. This conclusion affects the explanations for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and protostellar cores.

KW - interstellar ices

KW - pre-stellar

KW - protostellar

KW - astrophysics

KW - desorption experiments

U2 - 10.1051/0004-6361:20054051

DO - 10.1051/0004-6361:20054051

M3 - Article

VL - 449

SP - 1297

EP - 1309

JO - Astronomy and Astrophysics

T2 - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 3

ER -

Bisschop SE, Fraser HJ, Öberg KI, van Dishoeck EF, Schlemmer S. Desorption rates and sticking coefficients for CO and N2 interstellar ices. Astronomy and Astrophysics. 2006 Apr;449(3):1297-1309. https://doi.org/10.1051/0004-6361:20054051