Near-Interfacial Halogen Atom Exchange in Collisions of Cl<sub>2</sub> with 2.7 M NaBr–Glycerol

Dempsey, Logan P.; Faust, Jennifer A.; Nathanson, Gilbert M.

doi:10.1021/jp308202k

Cited by 10 publications

(49 citation statements)

References 71 publications

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“…This multistep process (adsorption/intercalation/de-intercalation/ desorption) would result in ⟨E f ⟩ TD < 2RT s if the O atoms had substantial residence times on the surface, because the desorption time would be decoupled from the time when the O-atom pulse collided with the surface, which is time zero (t = 0) for the analysis of the observed TOF distributions. 46 We estimate that the shortest detectable residence time in our experiment would be on the order of tens of microseconds. To determine the true ⟨E f ⟩ TD of the TD slow O atoms on HOPG at 1100 K, the analysis would need to account for the residence time, which is currently unknown and cannot be unambiguously determined from this set of data.…”

Section: Discussionmentioning

confidence: 73%

Dynamics of Graphite Oxidation at High Temperature

2018

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Interactions of ground-state atomic and molecular oxygen, O( 3 P) and O 2 ( 3 Σ g −), with a highly oriented pyrolytic graphite surface were investigated for a broad range of surface temperatures from 1100 K to approximately 2300 K. A molecular beam composed of 89% O atoms and 11% O 2 , with average translational energies of 472.1 and 944.4 kJ mol −1 , respectively, was directed at the surface with an incidence angle, θ i , of 45°. Angle-and velocity-resolved distributions were collected for nonreactively and reactively scattered products with the use of a rotatable mass spectrometer detector. Four scattered products were observed: O, O 2 , CO, and CO 2 . O atoms that exited the surface without reacting exhibited both impulsive scattering (IS) and thermal desorption (TD) components. The primary reaction product observed was carbon monoxide (CO). Carbon dioxide (CO 2 ) was measured only with surface temperatures below 1400 K, and O 2 was attributed to IS of O 2 that was present in the incident beam. Although there is evidence for either Eley−Rideal or hot atom reactions, CO and CO 2 were primarily formed by Langmuir−Hinshelwood (LH) reactions. However, the flux angular distributions of the LH products were significantly narrower than a cosine distribution, and the final energies were much higher than those predicted by the Maxwell−Boltzmann distribution characterized by the surface temperature. These observations indicate that CO and CO 2 that were produced by LH reactions desorb from the surface over a barrier. The desorption barrier of CO was determined by using the principle of detailed balance (where the desorption and adsorption barriers are equal) and was found to increase from 121 ± 5 kJ mol −1 at 1100 K to 155 ± 7 kJ mol −1 at 1300 K. As the surface temperature increased, the fluxes of CO and CO 2 produced by LH mechanisms decreased. Simultaneously, the flux of O atoms that scattered via the TD channel increased, which reduced the surface oxygen coverage at higher temperatures. The combination of reduced O-atom surface coverage and increased desorption barriers for CO suppresses the reactivity of the surface at high temperatures.

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Section: Discussionmentioning

confidence: 73%

Dynamics of Graphite Oxidation at High Temperature

2018

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“…In contrast, ClNO 2 is depleted near the interface due to evaporation to the atmosphere and reaches steady-state within 20 μs at a depth of d > 60 nm (Figure ). To test our model, we can extract the time-dependent solution for γ(N 2 O 5 ) from the calculation of [N 2 O 5 ] ( x =0, t ) and compare it with both the exact analytical solution (eq ) − for the case of reversible solubility with irreversible reaction (i.e., N 2 O 5 hydrolysis, reaction ), and the measured values of steady-state γ(N 2 O 5 ) for aqueous solutions (γ(N 2 O 5 ) = 0.03). where .…”

Section: Results and Discussionmentioning

confidence: 99%

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

Staudt

Gord

Karimova

et al. 2019

ACS Earth Space Chem.

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We report measurements of the nitryl chloride (ClNO 2 ) branching fraction following reactive uptake of N 2 O 5 to mixed organic and inorganic solutions representative of atmospheric interfaces. For sodium chloride containing solutions, mixed with either sodium sulfate (Na 2 SO 4 ) or sodium acetate (NaAc), the ClNO 2 branching fraction (Φ ClNO 2 ) is suppressed relative to a sodium chloride only solution. In the case of the sulfate-chloride solution, Φ ClNO 2 is reduced from 0.85 ± 0.03 (0.5 M NaCl) to 0.32 ± 0.14 upon the addition of 2.0 M Na 2 SO 4 . In the case of the acetate-chloride solution, Φ ClNO 2 is reduced to 0.18 ± 0.03 upon the addition of 0.5 M NaAc. In contrast, no statistically significant suppression in Φ ClNO 2 was observed for the addition of sodium perchlorate up to 3.0 M, implying that an increase in ionic strength of the solution does not necessitate a reduction in Φ ClNO 2 . We suggest that the reduction in Φ ClNO 2 may result from a direct reaction between SO 4 2− (and Ac − ) with NO 2 + (or NO 2 + NO 3 − ) which competes with the NO 2 + + Cl − reaction that produces ClNO 2 . The dependence of Φ ClNO 2 on SO 4 2− and Ac − is compared with both a time-dependent reaction-diffusion model and recent field observations, suggesting that the reaction rate of SO 4 2−(or Ac − ) with NO 2 + would need to be similar in magnitude to the rate of the NO 2 + + Cl − reaction to explain the observed suppression in Φ ClNO 2 . We show that the dependence of Φ ClNO 2 on particulate sulfate and carboxylate can be readily incorporated into existing parametrizations of ClNO 2 heterogeneous chemistry. The results presented here indicate that anions which are ubiquitous in atmospheric aerosol, yet commonly considered to be unreactive, may regulate the production of reactive gases such as ClNO 2 .

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“…Separate studies provide insights into the mechanism of dissolution and reaction. [39,45,46]. In all three cases, the product DCl or Br 2 evaporates in a Maxwellian distribution at the temperature of the liquid.…”

Section: Maxwellian Evaporation and A Two-step Model For Solvationmentioning

confidence: 90%

“…During 30 years of observation, we have monitored the vacuum evaporation of liquids such as glycerol, ethylene glycol, alkanes and aromatics, fluorinated ethers, and water from sulfuric acid and pure and salty water itself [39][40][41][42][43]. [39,40,42,[44][45][46][47][48]. We observed Maxwellian speed distributions in every case (except when the vapor pressure is so high that the gas expands supersonically [41,49]).…”

Section: Maxwellian Evaporation and A Two-step Model For Solvationmentioning

confidence: 99%

When Liquid Rays Become Gas Rays: Can Evaporation Ever Be Non-Maxwellian?

Nathanson

2021

Molecular Beams in Physics and Chemistry

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A rare mistake by Otto Stern led to a confusion between density and flux in his first measurement of a Maxwellian speed distribution. This error reveals the key role of speed itself in Stern’s development of “the method of molecular rays”. What if the gas-phase speed distributions are not Maxwellian to begin with? The molecular beam technique so beautifully advanced by Stern can also be used to explore the speed distribution of gases evaporating from liquid microjets, a tool developed by Manfred Faubel. We employ liquid water and alkane microjets containing dissolved helium atoms to monitor the speed of evaporating He atoms into vacuum. While most dissolved gases evaporate in Maxwellian speed distributions, the He evaporation flux is super-Maxwellian, with energies up to 70% higher than the flux-weighted average energy of 2 RTliq. The explanation of this high-energy evaporation involves two beautiful concepts in physical chemistry: detailed balancing between He atom evaporation and condensation (starting with gas-surface collisions) and the potential of mean force on the He atom (starting with He atoms just below the surface). We hope that these measurements continue to fulfill Stern’s dream of the “directness and simplicity of the molecular ray method.”

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Near-Interfacial Halogen Atom Exchange in Collisions of Cl₂ with 2.7 M NaBr–Glycerol

Cited by 10 publications

References 71 publications

Dynamics of Graphite Oxidation at High Temperature

Dynamics of Graphite Oxidation at High Temperature

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces

When Liquid Rays Become Gas Rays: Can Evaporation Ever Be Non-Maxwellian?

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Near-Interfacial Halogen Atom Exchange in Collisions of Cl2 with 2.7 M NaBr–Glycerol

Cited by 10 publications

References 71 publications

Dynamics of Graphite Oxidation at High Temperature

Dynamics of Graphite Oxidation at High Temperature

Sulfate and Carboxylate Suppress the Formation of ClNO2 at Atmospheric Interfaces

When Liquid Rays Become Gas Rays: Can Evaporation Ever Be Non-Maxwellian?

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Product

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Near-Interfacial Halogen Atom Exchange in Collisions of Cl₂ with 2.7 M NaBr–Glycerol

Sulfate and Carboxylate Suppress the Formation of ClNO₂ at Atmospheric Interfaces