Release of Oxygen Atoms and Nitric Oxide Molecules from the Ultraviolet Photodissociation of Nitrate Adsorbed on Water Ice Films at 100 K

Abstract

Production of O((3)P(J), J = 2, 1, 0) atoms from the 295-320 nm photodissociation of NO(3)- adsorbed on water polycrystalline ice films at 100 K was directly confirmed using the resonance-enhanced multiphoton ionization technique. Detection of the O atom signals required an induction period after deposition of HNO3 onto the ice film held at 130 K due to the slow ionization rate of HNO(3) to H+ and NO(3)- with a rate constant of k = (5.3 +/- 0.2) x 10(-3)s(-1). Translational energy distributions of the O atoms were represented by a combination of two Maxwell-Boltzmann energy distributions with translational temperatures of 2000 and 100 K. Direct detection of NO from the secondary photodissociation process was also successful. On the atmospheric implications, the influence of the direct release of the oxygen atoms into the air from NO(3)- adsorbed on the natural snowpack was included in an atmospheric model calculation on the mixing ratios of ozone and nitric oxide at the South Pole, and the results compared favorably with the field data.

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

“…10 There is increasing evidence, both theoretical and experimental, that the quantum yields for photolysis at interfaces are indeed significantly greater than in the bulk. [159][160][161][162][163][164][165][166][167][168] …”

“…Yabushita et al 167 reported the production of gas phase O( 3 P) with three different translational energies from photolysis of NO 3 À on ice at 193 nm; the fastest component was attributed to direct production from excited NO 3 À on the ice surface via reaction (10b). This was not detected for photolysis at 305 nm, however, which they suggested could be due to the smaller absorption cross sections as well as lower quantum yields for O( 3 P) formation at this longer wavelength.…”

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

“…Thus, the quantum yields for photolysis are larger when the ion is at the interface of aqueous solutions where there is an incomplete solvent cage. [107][108][109][110][111][112][113][114][115][116] The production of OH radicals via the well known photochemistry in bulk aqueous solutions 117,118 …”

The effect of cations on NO2 production from the photolysis of aqueous thin water films of nitrate salts

“…15,16 There is also evidence that the photolysis of species at the interface has higher quantum yields than those in the bulk. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] In short, interfacial kinetics and mechanisms may be significantly different compared to those in the bulk phase.…”