Translational and rotational energy measurements of desorbed water molecules in their vibrational ground state following 157 nm irradiation of amorphous solid water

Tetsuya Hama, Masaaki Yokoyama, Akihiro Yabushita, Masahiro Kawasaki, Naoki Watanabe

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1 Citation (Scopus)

Abstract

Water ice is the major solid component in a variety of astrophysical environments, e.g., cold and dense molecular clouds. Photodesorption plays a dominant role in consuming ice in such cold regions. In this study, photodesorption of vibrationally ground-state H2O(v = 0) from amorphous solid water has been investigated at 157 nm. Using a resonance-enhanced multiphoton ionization technique, the translational and rotational energy distributions of photodesorbed H2O(v = 0) were measured, i.e., Boltzmann distributions at 1800 and 300 K, respectively. These energies are in good accordance with those predicted by classical molecular calculations for water photodesorption due to a kick-out mechanism following absorption of a single photon; hot H atom released by photodissociation of H2O in ice transfers enough momentum to another H2O molecule to kick it off the surface. Desorption of D2O(v = 0) following 193 nm photoirradiation of a D2O/H2S mixed ice was investigated to provide further direct evidence for the operation of a kick-out mechanism. The other desorption mechanisms were also discussed in the context of possible photodesorption of vibrationally excited H2O.

Original languageEnglish
Pages (from-to)1011-1015
Number of pages5
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume269
Issue number9
DOIs
Publication statusPublished - May 1 2011
Externally publishedYes

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Electric power measurement
Ground state
Ice
ice
Irradiation
Molecules
irradiation
ground state
water
Water
molecules
Desorption
desorption
Photodissociation
Boltzmann distribution
Momentum transfer
energy
molecular clouds
photodissociation
Ionization

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Instrumentation

Cite this

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abstract = "Water ice is the major solid component in a variety of astrophysical environments, e.g., cold and dense molecular clouds. Photodesorption plays a dominant role in consuming ice in such cold regions. In this study, photodesorption of vibrationally ground-state H2O(v = 0) from amorphous solid water has been investigated at 157 nm. Using a resonance-enhanced multiphoton ionization technique, the translational and rotational energy distributions of photodesorbed H2O(v = 0) were measured, i.e., Boltzmann distributions at 1800 and 300 K, respectively. These energies are in good accordance with those predicted by classical molecular calculations for water photodesorption due to a kick-out mechanism following absorption of a single photon; hot H atom released by photodissociation of H2O in ice transfers enough momentum to another H2O molecule to kick it off the surface. Desorption of D2O(v = 0) following 193 nm photoirradiation of a D2O/H2S mixed ice was investigated to provide further direct evidence for the operation of a kick-out mechanism. The other desorption mechanisms were also discussed in the context of possible photodesorption of vibrationally excited H2O.",
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T1 - Translational and rotational energy measurements of desorbed water molecules in their vibrational ground state following 157 nm irradiation of amorphous solid water

AU - Hama, Tetsuya

AU - Yokoyama, Masaaki

AU - Yabushita, Akihiro

AU - Kawasaki, Masahiro

AU - Watanabe, Naoki

PY - 2011/5/1

Y1 - 2011/5/1

N2 - Water ice is the major solid component in a variety of astrophysical environments, e.g., cold and dense molecular clouds. Photodesorption plays a dominant role in consuming ice in such cold regions. In this study, photodesorption of vibrationally ground-state H2O(v = 0) from amorphous solid water has been investigated at 157 nm. Using a resonance-enhanced multiphoton ionization technique, the translational and rotational energy distributions of photodesorbed H2O(v = 0) were measured, i.e., Boltzmann distributions at 1800 and 300 K, respectively. These energies are in good accordance with those predicted by classical molecular calculations for water photodesorption due to a kick-out mechanism following absorption of a single photon; hot H atom released by photodissociation of H2O in ice transfers enough momentum to another H2O molecule to kick it off the surface. Desorption of D2O(v = 0) following 193 nm photoirradiation of a D2O/H2S mixed ice was investigated to provide further direct evidence for the operation of a kick-out mechanism. The other desorption mechanisms were also discussed in the context of possible photodesorption of vibrationally excited H2O.

AB - Water ice is the major solid component in a variety of astrophysical environments, e.g., cold and dense molecular clouds. Photodesorption plays a dominant role in consuming ice in such cold regions. In this study, photodesorption of vibrationally ground-state H2O(v = 0) from amorphous solid water has been investigated at 157 nm. Using a resonance-enhanced multiphoton ionization technique, the translational and rotational energy distributions of photodesorbed H2O(v = 0) were measured, i.e., Boltzmann distributions at 1800 and 300 K, respectively. These energies are in good accordance with those predicted by classical molecular calculations for water photodesorption due to a kick-out mechanism following absorption of a single photon; hot H atom released by photodissociation of H2O in ice transfers enough momentum to another H2O molecule to kick it off the surface. Desorption of D2O(v = 0) following 193 nm photoirradiation of a D2O/H2S mixed ice was investigated to provide further direct evidence for the operation of a kick-out mechanism. The other desorption mechanisms were also discussed in the context of possible photodesorption of vibrationally excited H2O.

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