Quantum Yields for Photochemical Production of NO2 from Organic Nitrates at Tropospherically Relevant Wavelengths

Christina M. Higgins, Louise A. Evans, Guy C. Lloyd-Jones, Dudley E. Shallcross, David P. Tew, Andrew J. Orr-Ewing*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

4 Citations (Scopus)
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Abstract

Absorption cross-sections and quantum yields for NO2 production (Phi(NO2)) are reported for gaseous methyl, ethyl, n-propyl, and isopropyl nitrate at 294 K. Absorption cross-sections in the wavelength range of 240-320 nm agree well with prior determinations. NO2 quantum yields at photoexcitation wavelengths of 290, 295, and 315 nm are unity within experimental uncertainties for all of the alkyl nitrates studied and are independent of bath gas (N-2) pressure for total sample pressures in the range of 250-700 Torr. When averaged over all wavelengths and sample pressures, values of Phi(NO2) are 1.03 +/- 0.05 (methyl nitrate), 0.98 +/- 0.09 (ethyl nitrate), 1.01 +/- 0.04 (n-propyl nitrate), and 1.00 +/- 0.05 (isopropyl nitrate), with uncertainties corresponding to 1 standard deviation. Absorption cross-sections for ethyl nitrate, isopropyl nitrate, and two unsaturated dinitrate compounds, but-3-ene-1,2-diyl dinitrate and (Z)-but-2-ene-1,4-diyl dinitrate in acetonitrile solution, are compared to gas-phase values, and over the wavelength range of 260-315 nm, the gas-phase values are well-reproduced by dividing the liquid-phase cross-sections by 2.0, 1.6, 1.7, and 2.2, respectively. Reasonable estimates of the gas-phase absorption cross-sections for low-volatility organic nitrates can therefore be obtained by halving the values for acetonitrile solutions. The quantum yield for NO2 formation from photoexcitation of but-3-ene-1,2-diyl dinitrate at 290 nm is significantly lower than those for the alkyl (mono) nitrates: a best estimate of Phi(NO2)

Original languageEnglish
Pages (from-to)2756-2764
Number of pages9
JournalJournal of Physical Chemistry A
Volume118
Issue number15
Early online date31 Mar 2014
DOIs
Publication statusPublished - 17 Apr 2014

Bibliographical note

Accepted 31/03/2014

Keywords

  • ABSORPTION CROSS-SECTIONS
  • ALKYL NITRATES
  • METHYL NITRATE
  • TEMPERATURE-DEPENDENCE
  • ATMOSPHERIC LIFETIMES
  • PHOTOLYSIS PRODUCTS
  • RATE COEFFICIENTS
  • EXCITED-STATES
  • ETHYL NITRATE
  • NITRIC-ACID

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