Quantum yields, Phi, for the production of the formyl radical, HCO, in the photolysis of glyoxal were determined at 85 wavelengths, lambda, in the range of 290-420 nm at pressures between 50 and 550 Torr (N-2) at 298 K using pulsed-laser photolysis combined with cavity ring-down spectroscopy detection of HCO. HCO quantum yields were parametrized using a Stern-Volmer analysis to obtain extrapolated zero-pressure NCO quantum yields, Phi(0)(lambda), and values for the ratio of the rate coefficients for quenching and dissociation, k(q)/k(d)(lambda), at each wavelength. Phi(0)(lambda) varied smoothly with wavelength with a maximum value of similar to 1.8 in the range 300-385 nm with values decreasing to near 0 at 420 nm and 0.4 at 290 nm. k(q)/k(d)(lambda) was measurable at nearly all photolysis wavelengths and is well-represented by the relationship k(q)/k(d)(lambda) = (2.3 x 10(-20)) +(1.5 x 10(-19)) exp(-0.4 Delta E) (cm(3) molecule(-1)) where Delta E = ((28 571/lambda) - 72.5) (kcal mol(-1)), lambda is the photolysis wavelength (nm), and 72.5 kcal mol(-1) is the threshold for glyoxal photodissociation. Differences in our HCO quantum yield wavelength- and pressure-dependence with previous studies are discussed. The present HCO quantum yield data are appropriate for use in atmospheric model calculations, and revised wavelength-dependent photolysis branching ratios for the production of 2HCO, H2CO + O-2 and H-2 + 2CO at atmospheric pressure are presented.
%0 Journal Article
%1 Feierabend:2009p2303
%A Feierabend, Karl J
%A Flad, Jonathan E
%A Brown, S. S
%A Burkholder, James B
%D 2009
%J Journal of Physical Chemistry A
%K A-1(U) Chemistry, Constants, Dissociation, Formaldehyde, Fragment Glyoxal, Hco, Photochemistry, Rate Relaxation, S-1 State, Trans-Glyoxal
%N 27
%P 7784--7794
%R 10.1021/jp9033003
%T HCO Quantum Yields in the Photolysis of HC(O)C(O)H (Glyoxal) between 290 and 420 nm
%U http://pubs.acs.org/doi/abs/10.1021/jp9033003
%V 113
%X Quantum yields, Phi, for the production of the formyl radical, HCO, in the photolysis of glyoxal were determined at 85 wavelengths, lambda, in the range of 290-420 nm at pressures between 50 and 550 Torr (N-2) at 298 K using pulsed-laser photolysis combined with cavity ring-down spectroscopy detection of HCO. HCO quantum yields were parametrized using a Stern-Volmer analysis to obtain extrapolated zero-pressure NCO quantum yields, Phi(0)(lambda), and values for the ratio of the rate coefficients for quenching and dissociation, k(q)/k(d)(lambda), at each wavelength. Phi(0)(lambda) varied smoothly with wavelength with a maximum value of similar to 1.8 in the range 300-385 nm with values decreasing to near 0 at 420 nm and 0.4 at 290 nm. k(q)/k(d)(lambda) was measurable at nearly all photolysis wavelengths and is well-represented by the relationship k(q)/k(d)(lambda) = (2.3 x 10(-20)) +(1.5 x 10(-19)) exp(-0.4 Delta E) (cm(3) molecule(-1)) where Delta E = ((28 571/lambda) - 72.5) (kcal mol(-1)), lambda is the photolysis wavelength (nm), and 72.5 kcal mol(-1) is the threshold for glyoxal photodissociation. Differences in our HCO quantum yield wavelength- and pressure-dependence with previous studies are discussed. The present HCO quantum yield data are appropriate for use in atmospheric model calculations, and revised wavelength-dependent photolysis branching ratios for the production of 2HCO, H2CO + O-2 and H-2 + 2CO at atmospheric pressure are presented.
@article{Feierabend:2009p2303,
abstract = {Quantum yields, Phi, for the production of the formyl radical, HCO, in the photolysis of glyoxal were determined at 85 wavelengths, lambda, in the range of 290-420 nm at pressures between 50 and 550 Torr (N-2) at 298 K using pulsed-laser photolysis combined with cavity ring-down spectroscopy detection of HCO. HCO quantum yields were parametrized using a Stern-Volmer analysis to obtain extrapolated zero-pressure NCO quantum yields, Phi(0)(lambda), and values for the ratio of the rate coefficients for quenching and dissociation, k(q)/k(d)(lambda), at each wavelength. Phi(0)(lambda) varied smoothly with wavelength with a maximum value of similar to 1.8 in the range 300-385 nm with values decreasing to near 0 at 420 nm and 0.4 at 290 nm. k(q)/k(d)(lambda) was measurable at nearly all photolysis wavelengths and is well-represented by the relationship k(q)/k(d)(lambda) = (2.3 x 10(-20)) +(1.5 x 10(-19)) exp(-0.4 Delta E) (cm(3) molecule(-1)) where Delta E = ((28 571/lambda) - 72.5) (kcal mol(-1)), lambda is the photolysis wavelength (nm), and 72.5 kcal mol(-1) is the threshold for glyoxal photodissociation. Differences in our HCO quantum yield wavelength- and pressure-dependence with previous studies are discussed. The present HCO quantum yield data are appropriate for use in atmospheric model calculations, and revised wavelength-dependent photolysis branching ratios for the production of 2HCO, H2CO + O-2 and H-2 + 2CO at atmospheric pressure are presented.},
added-at = {2010-06-22T19:38:37.000+0200},
affiliation = {NOAA, Earth Syst Res Lab, Div Chem Sci, Boulder, CO 80305 USA},
author = {Feierabend, Karl J and Flad, Jonathan E and Brown, S. S and Burkholder, James B},
biburl = {https://www.bibsonomy.org/bibtex/23ca9d6f2b8d129b04cddb15ae5a3cf79/gsmith},
date-added = {2010-03-23 15:14:27 -0400},
date-modified = {2010-03-23 15:14:39 -0400},
doi = {10.1021/jp9033003},
interhash = {cccea45fb3c4aa8a1aa88f0309e77486},
intrahash = {3ca9d6f2b8d129b04cddb15ae5a3cf79},
journal = {Journal of Physical Chemistry A},
keywords = {A-1(U) Chemistry, Constants, Dissociation, Formaldehyde, Fragment Glyoxal, Hco, Photochemistry, Rate Relaxation, S-1 State, Trans-Glyoxal},
language = {English},
local-url = {file://localhost/Users/geoffreysmith/Documents/Papers/Journal%20of%20Physical%20Chemistry%20A/2009/Journal%20of%20Physical%20Chemistry%20A,%20113,%207784-7794%202009.pdf},
month = Jan,
number = 27,
pages = {7784--7794},
pmid = {000267694800013},
rating = {0},
timestamp = {2010-06-22T19:39:00.000+0200},
title = {HCO Quantum Yields in the Photolysis of HC(O)C(O)H (Glyoxal) between 290 and 420 nm},
uri = {papers://E88B624E-D406-46FF-9D95-BB9C1AAE3FDC/Paper/p2303},
url = {http://pubs.acs.org/doi/abs/10.1021/jp9033003},
volume = 113,
year = 2009
}