Photoabsorption Spectra of Ammonia in 1050 to 2250 Å Region

Saraswathy, P.; Krishnakumar, S.; Aparna, S.; Sekhar, B. N. Raja

doi:10.1080/00387010903338335

Cited by 8 publications

(11 citation statements)

References 15 publications

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“…Therefore, spectral measures in the VUV range are usually carried out under vacuum or in an inert (nonabsorbing) gas atmosphere. 174 In addition to being a possible source of ozone by air (or oxygen) irradiation, as an alternative to electrochemical O 3 generation, 175 VUV radiation is also a suitable technique to produce • OH upon water photolysis. 176 Historically, VUV photolysis has first been applied to water vapor as a source of gas-phase hydroxyl radicals for kinetic studies.…”

Section: •−mentioning

confidence: 99%

“…This spectral range is usually called vacuum ultraviolet (VUV) because radiation of this wavelength cannot travel in air due to absorption by oxygen, which is subsequently transformed into ozone by photolysis. Therefore, spectral measures in the VUV range are usually carried out under vacuum or in an inert (nonabsorbing) gas atmosphere . In addition to being a possible source of ozone by air (or oxygen) irradiation, as an alternative to electrochemical O 3 generation, VUV radiation is also a suitable technique to produce • OH upon water photolysis …”

Section: Generation Of •Oh Radicals Under Controlled Laboratory Condi...mentioning

confidence: 99%

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Environmental Implications of Hydroxyl Radicals (^•OH)

et al. 2015

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The hydroxyl radical ((•)OH) is one of the most powerful oxidizing agents, able to react unselectively and instantaneously with the surrounding chemicals, including organic pollutants and inhibitors. The (•)OH radicals are omnipresent in the environment (natural waters, atmosphere, interstellar space, etc.), including biological systems where (•)OH has an important role in immunity metabolism. We provide an extensive view on the role of hydroxyl radical in different environmental compartments and in laboratory systems, with the aim of drawing more attention to this emerging issue. Further research on processes related to the hydroxyl radical chemistry in the environmental compartments is highly demanded. A comprehensive understanding of the sources and sinks of (•)OH radicals including their implications in the natural waters and in the atmosphere is of crucial importance, including the way irradiated chromophoric dissolved organic matter in surface waters yields (•)OH through the H2O2-independent pathway, and the assessment of the relative importance of gas-phase vs aqueous-phase reactions of (•)OH with many atmospheric components. Moreover, considering the fact that people spend so much more time in dwellings than outside, the impact of the reactivity of indoor hydroxyl radicals on health and well-being is another emerging research topic of great concern.

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Section: •−mentioning

confidence: 99%

Section: Generation Of •Oh Radicals Under Controlled Laboratory Condi...mentioning

confidence: 99%

Environmental Implications of Hydroxyl Radicals (^•OH)

et al. 2015

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“…Two additional absorption bands have been observed in the NH 3 spectrum at wavelengths longer than 220 nm. These hot bands have been observed at pressures greater than 15 Torr, or temperatures greater than 150 °C . Because these hot bands correspond to wavelengths with plentiful photons, this effect could potentially offset the decreased deposition rate expected at higher temperatures due to a lower population of physisorbed reactant molecules.…”

Section: Discussionmentioning

confidence: 96%

Ammonia Photodissociation Promoted by Si(100)

Finstad

Muscat

2014

J. Phys. Chem. A

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Using in situ X-ray photoelectron spectroscopy measurements after reaction, we show that hydrogen-terminated Si(100) perturbs the bonding of physisorbed NH3 enabling a photochemical decomposition pathway at wavelengths different from those characteristic of either the molecule in the gas phase or the semiconductor bandgap. UV illumination only of gas phase NH3 at partial pressures from 0.1 to 100 Torr produced a maximum at 10 Torr in the N surface coverage. This is in good agreement with a model of the radical production rate showing that at this pressure the gas density balances the flux of photons at the surface with energies sufficient to dissociate NH3. UV illumination of both the gas phase and the surface produced a monotonic increase in the N coverage with pressure as well as coverages that were 3-10 times higher than when only the gas phase was illuminated. The amine saturation coverage scaled with the UV fluence at 10 Torr and 75 °C, reaching 6.9 × 10(14) atoms/cm(2) (∼1 N atom per Si surface atom) at 19 mW/cm(2) and 12 × 10(14) atoms/cm(2) (∼1.8 N per Si) at 35 mW/cm(2). Monochromatic illumination showed that the wavelengths driving deposition were not correlated with the Si bandgap, but instead were roughly the same as gas phase photodissociation (λ < 220 nm). The primary driving force to replace the hydrogen termination with amine groups was direct photodissociation of NH3 molecules whose electronic structure was perturbed by interaction with the surface. Amine groups enhanced the surface reaction of water present as a contaminant in the source gas. These results show that molecules in weakly bound surface states can have a dramatic impact on the photochemistry.

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“…The key features within this band have been studied by experimental methods, 2,3,7,13,[20][21][22][28][29][30]40,51,69 and also through different levels of theory. 56,57,59,62,63 The photoabsorption spectrum in the 5.4-7.6 eV energy region is presented in Fig.…”

Section: A Theã-state Of Ammoniamentioning

confidence: 99%