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

Abstract

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.

Effect of Coadsorbed Oxygen on the Photochemistry of Methane Embedded in Amorphous Solid Water

“…Kang et al also studied the reactivity of nitrogen dioxide with ASW at low temperatures. They realized that the conversion efficiency of NO 2 on the ice surface at a low temperature is significantly higher than on the surface of liquid water at room temperature. , …”

“…They realized that the conversion efficiency of NO 2 on the ice surface at a low temperature is significantly higher than on the surface of liquid water at room temperature. 47,48 Here, we focus mainly on the photochemical reaction and the excitation mechanism of CH 4 sandwiched within two layers of ASW and ASW|CH 4 |O 2 |ASW on Ru(0001) substrate using excimer laser irradiation at 248 nm (5.0 eV photon energy). We demonstrate how methane conversion takes place near oxygen molecules entrapped in ASW ice, analogous to the conditions found in the interstellar ice upon UV irradiation that exists in that medium.…”

Shell model states in the continuum

“…To test our SS-HORSE technique, we calculate the phase shifts and resonant parameters of nα scattering in a two-body approach treating neutron and α as structureless particles whose interaction is described by the potential WSBG of a Woods-Saxon type with parameters fitted by Bang and Gignoux [49]:…”

Introductory lecture: atmospheric chemistry in the Anthropocene

“…Other potential sources of HONO in the atmosphere include NO 2 dark reactions with soot [174][175][176][177][178][179][180][181][182][183][184][185][186] and with organics, [187][188][189][190] photoenhanced interactions of NO 2 on both inorganic and organic surfaces, [191][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206][207] and photolysis of o-nitrophenols. 201,208 Photocatalysis by TiO 2 and components of mineral dust and building materials has also been shown to cause the conversion of NO 2 to HONO.…”