Knudsen layer formation in laser induced thermal desorption

Ikeda, Akihiko; Matsumoto, M.; Ogura, Shohei; Okano, Tatsuo; Fukutani, Katsuyuki

doi:10.1063/1.4795827

Cited by 12 publications

(3 citation statements)

References 38 publications

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“…24,25 Alternatively, the laser energy can be coupled into the substrate to induce the thermal desorption of ice constituents. 28,29,[33][34][35][36] The desorbed ice constituents are subsequently ionised, for example, using electron impact ionisation, and analysed with a TOF-MS.…”

Section: Introductionmentioning

confidence: 99%

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Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

Paardekooper

Bossa

Isokoski

et al. 2014

Review of Scientific Instruments

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A new ultra-high vacuum experiment is described that allows studying photo-induced chemical processes in interstellar ice analogues. MATRI(2)CES - a Mass Analytical Tool to study Reactions in Interstellar ICES applies a new concept by combining laser desorption and time-of-flight mass spectrometry with the ultimate goal to characterize in situ and in real time the solid state evolution of organic compounds upon UV photolysis for astronomically relevant ice mixtures and temperatures. The performance of the experimental setup is demonstrated by the kinetic analysis of the different photoproducts of pure methane (CH4) ice at 20 K. A quantitative approach provides formation yields of several new species with up to four carbon atoms. Convincing evidence is found for the formation of even larger species. Typical mass resolutions obtained range from M/ΔM ∼320 to ∼400 for CH4 and argon, respectively. Additional tests show that the typical detection limit (in monolayers) is ⩽0.02 ML, substantially more sensitive than the regular techniques used to investigate chemical processes in interstellar ices.

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Section: Introductionmentioning

confidence: 99%

“…The time label indicates time difference between laser pulse and ion extraction of ions to the flight tube. Panel (a) shows the overview, focussing on the argon isotopes,36 Ar + and 38 Ar + . Panel (b) shows the main40 Ar + peak.…”

mentioning

confidence: 99%

Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

Paardekooper

Bossa

Isokoski

et al. 2014

Review of Scientific Instruments

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“…However, in the vicinity of a wall, the isotropy is locally lost in a region, often called the Knudsen layer [2], where the atom-wall collisions modify the behavior of the gas. The microscopic description of an atom-surface collision or interaction is a rich field, which has been addressed experimentally for a long time.…”

Section: ~85°-885° From the Normal To The Surface And No Deviation mentioning

confidence: 99%

Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell

Todorov

Bloch

2017

The Journal of Chemical Physics

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2 For a gas at thermal equilibrium, it is usually assumed that the velocity distribution follows an isotropic 3-dimensional Maxwell-Boltzmann (M-B) law. This assumption classically implies the assumption of a "cos ~85°-88.5° from the normal to the surface and no deviation from the M-B law is found within the limits of our elementary set-up. Finally we suggest tracks to explore more parallel velocities, when surface details -roughness or structureand the atom-surface interaction should play a key role to restrict the applicability of a M-B-type distribution.3 I. The Maxwell-Boltzmann distribution of atomic velocities in a dilute gas and the signature of atoms moving close to a wall container.It is usually unquestioned, in the field of Atomic and Molecular Physics, that the atomic velocity distribution in a gas at thermal equilibrium is governed by a MaxwellBoltzmann (M-B) distribution for kinetic energy, with a 3-dimensional isotropy. This is even the basis for proposals aiming to measure the Boltzmann constant by the Doppler broadening of a thermal gas, in view of a redefinition of the temperature scale [1].However, in the vicinity of a wall, the isotropy is locally lost in a region, often called the Knudsen layer [2], where the atom-wall collisions modify the behavior of the gas. The microscopic description of an atom-surface collision or interaction is a rich field, which has been addressed experimentally for a long time. The possibility of a velocity distribution depending upon the vessel shape, has been sometimes considered, although the proofs for self-consistency seem delicate [3]. Despite the variety of behaviors found microscopically at the frontier of the gas, it remains usually assumed that the overall gas behavior obeys a M-B distribution (see e.g. [4]).As recalled in detail in the review by Comsa and David [5], which includes a significant historical approach, the distribution of atomic velocities established by Maxwell for an isotropic volume of a gas with molecules undergoing numerous collisions (the basis for the ideal gas kinetics) has been founded upon questionable hypotheses concerning the effect of the surface. The Maxwell model assumes that a fraction f of the molecules sticks onto the wall, for further scattering or "desorption" according to the expected "gas law", while the remaining fraction (1-f) just undergoes an ideal (specular) reflection on the wall.Retrospectively, it is clear that specular atomic reflection cannot be considered as a general 4 phenomenon for an unprepared surface and a high atomic density. Rather, quantum reflection on a wall potential is an effect well identified but difficult to observe, and applies to atoms cooled to extremely slow motion [6] (along the normal), while requiring perfectly polished surfaces [7]. For the desorption process, occurring on considerably longer time scale, arguments based upon conservation laws of the flux to and from the surface, combined with the assumed isotropic M-B distribution in the surrounding gas, lead to the cos law (Knudsen l...

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Dependence of device behaviours on oxygen vacancies in ZnSnO thin-film transistors

Zhang

Lü

et al. 2019

Appl. Phys. A

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Knudsen layer formation in laser induced thermal desorption

Cited by 12 publications

References 38 publications

Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell

Dependence of device behaviours on oxygen vacancies in ZnSnO thin-film transistors

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