Reactive Ion Scattering of Low Energy Cs<sup>+</sup>from Surfaces. A Technique for Surface Molecular Analysis

Kang, Heon

doi:10.5012/bkcs.2011.32.2.389

Cited by 29 publications

(47 citation statements)

References 65 publications

(108 reference statements)

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“…30,31 The chamber background pressure was maintained below 1 × 10 −10 Torr during the experiments. Acetone, water, and CCl 4 samples were prepared in the form of thin films grown on a Ru(0001) single-crystal substrate.…”

Section: Experimental Methodsmentioning

confidence: 99%

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

et al. 2014

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We investigated the phase transformations of amorphous solid acetone under confined geometry by preparing acetone films trapped in amorphous solid water (ASW) or CCl4. Reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) were used to monitor the phase changes of the acetone sample with increasing temperature. An acetone film trapped in ASW shows an abrupt change in the RAIRS features of the acetone vibrational bands during heating from 80 to 100 K, which indicates the transformation of amorphous solid acetone to a molecularly aligned crystalline phase. Further heating of the sample to 140 K produces an isotropic solid phase, and eventually a fluid phase near 157 K, at which the acetone sample is probably trapped in a pressurized, superheated condition inside the ASW matrix. Inside a CCl4 matrix, amorphous solid acetone crystallizes into a different, isotropic structure at ca. 90 K. We propose that the molecularly aligned crystalline phase formed in ASW is created by heterogeneous nucleation at the acetone-water interface, with resultant crystal growth, whereas the isotropic crystalline phase in CCl4 is formed by homogeneous crystal growth starting from the bulk region of the acetone sample.

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Section: Experimental Methodsmentioning

confidence: 99%

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

et al. 2014

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“…These intensity drops are thought to be due to changes in the ice surface morphology that affect the scattering efficiency of Cs + ions, rather than due to changes in the population of surface species. 19,23 Structural transformation of the ice surface may possibly cause this change, as has been observed for an amorphous solid water (ASW) film at a similar temperature (∼120 K) in previous studies. 23 Also, the reaction of NO 2 may disrupt the original crystallinity of the ice surface, thereby reducing the scattering efficiency of Cs + ions.…”

Section: -B Temperature-dependent Variation Of Surfacementioning

confidence: 76%

Reaction of Nitrogen Dioxide with Ice Surface at Low Temperature (≤170 K)

et al. 2015

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We studied the adsorption and reaction of nitrogen dioxide gas on the surface of an ice film at temperatures of 100−170 K under ultrahigh vacuum (UHV) conditions. Cs + reactive ion scattering (RIS) and low-energy sputtering (LES) techniques were used to identify and quantify the reactants and products on the surface of the ice film, in conjunction with the use of temperature-programmed desorption (TPD) to monitor the species desorbed. Temperature-ramping experiments were performed to examine the changes in the populations of these species as a function of temperature. Adsorption of NO 2 gas on the ice film at <110 K produced physisorbed species that may possibly possess negative charge character (NO 2 δ-), as deduced from the NO 2 and NO 2 − signals in the RIS and LES experiments. At 110−130 K, NO 2 δ-species were either desorbed as NO 2 gas or converted to nitrous acid (HONO), NO 3 − , and H 3 O + on the surface. Nitrous acid gas was desorbed at 140−160 K. The efficiency of conversion of NO 2 to surface nitrous acid was about 40%, and that to nitrous acid gas was about 7%. The efficiency of the reaction of NO 2 on the ice surface may be higher than that at the gas/liquid water interface. The reaction efficiency increased with a decrease of the NO 2 coverage and was inversely correlated with the N 2 O 4 coverage, which favors the mechanistic interpretation that an isolated NO 2 molecule reacts with water. However, NO 2 can diffuse on the ice surface to form clusters at ≥120 K. Under these conditions, the possibility that dimerization of NO 2 contributes to the hydrolysis reaction of NO 2 may not be excluded.

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“…We carried out the experiments in a UHV surface analysis chamber [40] equipped with instrumentation for Cs + reactive ion scattering, low-energy sputtering, reflection-absorption infrared spectroscopy, and temperature-programmed desorption measurements. A water film was prepared on a single-crystal Ru(0001) surface maintained at a desired temperature between 60 and 140 K by back-filling the chamber with water vapour (H 2 O or D 2 O) at a partial pressure of about 1 10 À8 torr.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, RIS and LES signals reveal the identities of neutral (X) and ionic species (Y + ), respectively, on the surface. [40,43] RAIRS provided additional molecular information about the water films through the detection of vibrational bands, thus satisfying the dipole selection rules in a reflection-absorption experiment. [44] The RAIRS experiments employed a grazing reflection geometry at an angle of 848 and a spectral resolution of 4 cm À1 in the range of 800-4000 cm À1 using a commercial FTIR instrument (PerkinElmer, Spectrum 100).…”

Section: à2mentioning

confidence: 99%

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Spectroscopic Monitoring of the Acidity of Water Films on Ru(0001): Orientation‐Specific Acidity of Adsorbed Water

Youngsoon

Shin

Moon

et al. 2014

Chemistry A European J

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Abstract:We examined the acid-base properties of water films adsorbed onto a Ru(0001) substrate by using surface spectroscopic methods in vacuum environments. Ammonia adsorption experiments combined with low-energy sputtering (LES), reactive ion scattering (RIS), reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) measurements showed that the adsorbed water is acidic enough to transfer protons to ammonia. Only the water molecules in an intact water monolayer and water clusters larger than the hexamer exhibit such acidity, whereas small clusters, a thick ice film or a partially dissociated water monolayer that contains OH, H 2 O and H species are not acidic. The observations indicate the orientation-specific acidity of adsorbed water. The acidity stems from water molecules with H-down adsorption geometry present in the monolayer. However, the dissociation of water into H and OH on the surface does not promote but rather suppresses the proton transfer to ammonia.

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Reactive Ion Scattering of Low Energy Cs⁺from Surfaces. A Technique for Surface Molecular Analysis

Cited by 29 publications

References 65 publications

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

Reaction of Nitrogen Dioxide with Ice Surface at Low Temperature (≤170 K)

Spectroscopic Monitoring of the Acidity of Water Films on Ru(0001): Orientation‐Specific Acidity of Adsorbed Water

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Reactive Ion Scattering of Low Energy Cs+from Surfaces. A Technique for Surface Molecular Analysis

Cited by 29 publications

References 65 publications

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

Phase Transitions of Amorphous Solid Acetone in Confined Geometry Investigated by Reflection Absorption Infrared Spectroscopy

Reaction of Nitrogen Dioxide with Ice Surface at Low Temperature (≤170 K)

Spectroscopic Monitoring of the Acidity of Water Films on Ru(0001): Orientation‐Specific Acidity of Adsorbed Water

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Reactive Ion Scattering of Low Energy Cs⁺from Surfaces. A Technique for Surface Molecular Analysis