Adsorption and ionization of HCl on an ice surface

Banham, Sally F.; Sodeau, John R.; Horn, Andrew B.; McCoustra, Martin R. S.; Chesters, M.A.

doi:10.1116/1.580307

Cited by 55 publications

(98 citation statements)

References 20 publications

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“…30,31,34,35 This observation strongly suggests that solvation and ionization dominate the interaction of HCl and HBr with both crystalline and amorphous microporous ice films at 110 K:…”

Section: Discussionmentioning

confidence: 88%

“…The line positions observed are in good agreement with similar transmission and reflection absorption spectra in the literature. 30,31 No other absorptions were observable over the entire mid infrared range of our detector (4000-650 cm -1 ), suggesting our hydrogen halide samples were free from impurities that absorb in the mid infrared. Following vapor deposition of the hydrogen halides, the temperature was increased at a rate of 10 K min -1 and the hydrogen halide films rapidly desorbed.…”

Section: Resultsmentioning

confidence: 93%

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Investigation of the Heterogeneous Reactivity of HCl, HBr, and HI on Ice Surfaces

1999

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The interactions of hydrogen halide gases (HX ) HCl, HBr, and HI) with thin ice films representative of atmospheric aerosols have been studied using a Knudsen cell reactor coupled to a Fourier transform infraredreflection absorption (FTIR-RAS) spectroscopic probe. The gas-phase uptake and reaction products resulting from the exposure of hydrogen halides to ice surfaces over a wide range of temperatures (110-210 K), hydrogen halide partial pressures (5-1000 × 10 -7 Torr), and ice film thicknesses (10-100 nm) are reported. Studies of HCl and HBr showed efficient reactions on crystalline and amorphous microporous ice films at 110 K to form H 3 O + until reaching coverages ranging from (5-20) × 10 15 molecules cm -2 , after which the rate of reaction dramatically decreased. The uptake of HCl on hexagonal crystalline ice at temperatures representative of the lower stratosphere and upper troposphere (180-210 K) was found to depend strongly on HCl partial pressure. Over the temperature range studied, exposure of ice to HCl partial pressures below the HCl equilibrium partial pressure at the liquid/ice coexistence point resulted in uptake limited to (3.5 ( 1.6) × 10 15 molecules cm -2 . In contrast, exposure to HCl pressures larger than the HCl equilibrium partial pressure resulted in unlimited uptake. HBr and HI were efficiently and continuously taken up by ice surfaces (γ g 0.02) over a range of atmospherically relevant temperatures (180-210 K). Although crystalline hydrates of HX:H 2 O are stable over the temperature range examined, the incorporation of hydrogen halides into ice always resulted in the formation of amorphous HX:H 2 O product layers with the exception of HBr uptake at high flow rates (flow rate g 3.1 × 10 15 molecules s -1 ) which resulted in the formation of a mixture of crystalline hydrates.

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“…30,31,34,35 This observation strongly suggests that solvation and ionization dominate the interaction of HCl and HBr with both crystalline and amorphous microporous ice films at 110 K:…”

Section: Discussionmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 93%

Investigation of the Heterogeneous Reactivity of HCl, HBr, and HI on Ice Surfaces

1999

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“…6,39,40 Of particular relevance to this work is the observation that the hexahydrate phase, HCl͑H 2 O) 6 , has not been observed to nucleate from the solid, but rather the melt supercooled to ϳ170 K, 38,39 with an HCl vapor pressure barrier of 5ϫ10 Ϫ5 torr. 31 Considerable work in this area is concerned with the possible dissociation of HCl on the surface, and with respect to the state of work in 1992, when the quasiliquid state was first proposed, ab initio and molecular dynamics calculations confirmed that HCl ionic dissociation was thermodynamically possible. 41,42 Later it was predicted that liquid formation was not necessary to promote dissociation on the surface.…”

Section: Introductionmentioning

confidence: 89%

“…Other studies report that complete ionization is observed spectroscopically at higher temperatures. 31,49 In other experiments above ϳ100 K a temperature dependent state of ionization is reported by Cs ϩ ion scattering, 50 and complete dissociation is measured by secondary-ion-mass spectroscopy, 51 near-edge x-ray absorption fine structure, 52 and temperature programmed desorption mass spectroscopy 53 techniques. Uptake experiments under conditions relevant to the upper atmosphere have indicated a dissociated state of adsorbed HCl.…”

Section: Introductionmentioning

confidence: 99%

“…The diffusion constants of HCl in/on H 2 O ice, measured since the advent of recent PSC research, have varied from Dϳ10 Ϫ11 to 10 Ϫ4 cm 2 /s. 12,[27][28][29][30][31][32][33][34][35][36][37] There is considerable contention regarding the experiments on diffusion within thin ice films. 35,36 This has nevertheless been convincingly worked out by careful analysis of temperature dependence, thermodynamics, and, most importantly, the crucial role of ice sample morphology by Domine et al, 29,30,36 who favor a stratospheric value of Dϳ10 Ϫ17 cm 2 /s.…”

Section: Introductionmentioning

confidence: 99%

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Experimental isotherms of HCl on H2O ice under stratospheric conditions: Connections between bulk and interfacial thermodynamics

Henson

Wilson

Robinson

et al. 2004

The Journal of Chemical Physics

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The adsorption of HCl on the surface of H(2)O ice has been measured at temperatures and pressures relevant to the upper troposphere and lower stratosphere. The measured HCl surface coverage is found to be at least 100 times lower than currently assumed in models of chlorine catalyzed ozone destruction in cold regions of the upper atmosphere. Measurements were conducted in a closed system by simultaneous application of surface spectroscopy and gas phase mass spectrometry to fully characterize vapor/solid equilibrium. Surface adsorption is clearly distinguished from bulk liquid or solid phases. From 180 to 200 K, submonolayer adsorption of HCl is well described by a Bragg-Williams modified Langmuir model which includes the dissociation of HCl into H(+) and Cl(-) ions. Furthermore, adsorption is consistent with two distinct states on the ice substrate, one in which the ions only weakly adsorb on separate sites, and another where the ions adsorb as an H(+)-Cl(-) pair on a single site with adsorption energy comparable to the bulk trihydrate. The number of substrate H(2)O molecules per adsorption site is also consistent with the stoichiometry of bulk hydrates under these conditions. The ionic states exist in equilibrium, and the total adsorption energy is a function of the relative population of both states. These observations and model provide a quantitative connection between the thermodynamics of the bulk and interfacial phases of HCl/H(2)O, and represent a consistent physicochemical model of the equilibrium system.

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Electrophilic Addition Reaction of Ethene with Hydrogen Chloride on Cold Molecular Films: Evidence of Ethyl Cationic Intermediate

Lee

Kim

et al. 2010

Chemistry An Asian Journal

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We studied the initial-stage mechanism of the electrophilic addition reaction of ethene with HCl by examining the interactions between ethene and HCl on water-ice and frozen molecular films at temperatures of 80-140 K. Cs(+) reactive ion scattering (RIS) and low-energy sputtering (LES) techniques were used to probe the reaction intermediates that were kinetically trapped on the surface, in conjunction with temperature-programmed desorption (TPD) mass spectrometry to monitor the desorbing species. The reaction initially produced the π complex of HCl and ethene at temperatures below about 93 K and an "ethyl cationic species" at temperatures below about 100 K. The ethyl cationic species was formed via direct proton transfer from the HCl molecule to ethene with the assistance of water solvation, rather than via the interaction of hydronium ions and ethene. At high temperatures, this species dissociated into ethene and hydronium and chloride ions. The reaction did not, however, complete the final transition state on the ice surface to produce ethyl chloride. The observation gives evidence that the electrophilic addition reaction of ethene occurs through an ethyl-like intermediate with an ionic character.

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Adsorption and ionization of HCl on an ice surface

Cited by 55 publications

References 20 publications

Investigation of the Heterogeneous Reactivity of HCl, HBr, and HI on Ice Surfaces

Investigation of the Heterogeneous Reactivity of HCl, HBr, and HI on Ice Surfaces

Experimental isotherms of HCl on H2O ice under stratospheric conditions: Connections between bulk and interfacial thermodynamics

Electrophilic Addition Reaction of Ethene with Hydrogen Chloride on Cold Molecular Films: Evidence of Ethyl Cationic Intermediate

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