Photodesorption of CO Ice

Karin I. Öberg, Guido W. Fuchs, Zainab Awad, Helen J. Fraser, Stephan Schlemmer, Ewine F. van Dishoeck, Harold Linnartz

Research output: Contribution to journalArticle

132 Citations (Scopus)

Abstract

At the high densities and low temperatures found in star-forming regions, all molecules other than H2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible, and hence a nonthermal desorption mechanism is necessary to maintain molecules in the gas phase. Here the first laboratory study of the photodesorption of pure CO ice under ultra-high vacuum conditions is presented, which gives a desorption rate of CO molecules per UV (7-10.5 eV) photon at 15 K. This rate is factors of larger than previously estimated and is comparable to estimates of other nonthermal desorption rates. The experiments constrain the mechanism to a single photon desorption process of ice surface molecules. The measured efficiency of this process shows that the role of CO photodesorption in preventing total removal of molecules in the gas has been underestimated.
LanguageEnglish
PagesL23-L26
Number of pages5
JournalAstrophysical Journal
Volume662
Issue number1
DOIs
Publication statusPublished - 10 Jun 2007

Fingerprint

desorption
ice
molecules
photons
gas
ultrahigh vacuum
dust
vapor phases
timescale
stars
life (durability)
temperature
estimates
gases
rate
experiment

Keywords

  • photodesorption
  • ice
  • vacuum
  • gas
  • nonthermal desorption
  • CO

Cite this

Öberg, K. I., Fuchs, G. W., Awad, Z., Fraser, H. J., Schlemmer, S., van Dishoeck, E. F., & Linnartz, H. (2007). Photodesorption of CO Ice. Astrophysical Journal, 662(1), L23-L26. https://doi.org/10.1086/519281
Öberg, Karin I. ; Fuchs, Guido W. ; Awad, Zainab ; Fraser, Helen J. ; Schlemmer, Stephan ; van Dishoeck, Ewine F. ; Linnartz, Harold. / Photodesorption of CO Ice. In: Astrophysical Journal. 2007 ; Vol. 662, No. 1. pp. L23-L26.
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abstract = "At the high densities and low temperatures found in star-forming regions, all molecules other than H2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible, and hence a nonthermal desorption mechanism is necessary to maintain molecules in the gas phase. Here the first laboratory study of the photodesorption of pure CO ice under ultra-high vacuum conditions is presented, which gives a desorption rate of CO molecules per UV (7-10.5 eV) photon at 15 K. This rate is factors of larger than previously estimated and is comparable to estimates of other nonthermal desorption rates. The experiments constrain the mechanism to a single photon desorption process of ice surface molecules. The measured efficiency of this process shows that the role of CO photodesorption in preventing total removal of molecules in the gas has been underestimated.",
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Öberg, KI, Fuchs, GW, Awad, Z, Fraser, HJ, Schlemmer, S, van Dishoeck, EF & Linnartz, H 2007, 'Photodesorption of CO Ice' Astrophysical Journal, vol. 662, no. 1, pp. L23-L26. https://doi.org/10.1086/519281

Photodesorption of CO Ice. / Öberg, Karin I.; Fuchs, Guido W.; Awad, Zainab; Fraser, Helen J.; Schlemmer, Stephan; van Dishoeck, Ewine F.; Linnartz, Harold.

In: Astrophysical Journal, Vol. 662, No. 1, 10.06.2007, p. L23-L26.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Photodesorption of CO Ice

AU - Öberg, Karin I.

AU - Fuchs, Guido W.

AU - Awad, Zainab

AU - Fraser, Helen J.

AU - Schlemmer, Stephan

AU - van Dishoeck, Ewine F.

AU - Linnartz, Harold

PY - 2007/6/10

Y1 - 2007/6/10

N2 - At the high densities and low temperatures found in star-forming regions, all molecules other than H2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible, and hence a nonthermal desorption mechanism is necessary to maintain molecules in the gas phase. Here the first laboratory study of the photodesorption of pure CO ice under ultra-high vacuum conditions is presented, which gives a desorption rate of CO molecules per UV (7-10.5 eV) photon at 15 K. This rate is factors of larger than previously estimated and is comparable to estimates of other nonthermal desorption rates. The experiments constrain the mechanism to a single photon desorption process of ice surface molecules. The measured efficiency of this process shows that the role of CO photodesorption in preventing total removal of molecules in the gas has been underestimated.

AB - At the high densities and low temperatures found in star-forming regions, all molecules other than H2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible, and hence a nonthermal desorption mechanism is necessary to maintain molecules in the gas phase. Here the first laboratory study of the photodesorption of pure CO ice under ultra-high vacuum conditions is presented, which gives a desorption rate of CO molecules per UV (7-10.5 eV) photon at 15 K. This rate is factors of larger than previously estimated and is comparable to estimates of other nonthermal desorption rates. The experiments constrain the mechanism to a single photon desorption process of ice surface molecules. The measured efficiency of this process shows that the role of CO photodesorption in preventing total removal of molecules in the gas has been underestimated.

KW - photodesorption

KW - ice

KW - vacuum

KW - gas

KW - nonthermal desorption

KW - CO

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Öberg KI, Fuchs GW, Awad Z, Fraser HJ, Schlemmer S, van Dishoeck EF et al. Photodesorption of CO Ice. Astrophysical Journal. 2007 Jun 10;662(1):L23-L26. https://doi.org/10.1086/519281