Wavelength Dependence of Primary Ozone Formation
J. Phys. Chem. A, Vol. 107, No. 7, 2003 1017
effect that lowers the photodissociation probability is effective.
The sum of heat of formation for O3 and CO (425 kJ mol )
no appreciable cage effect is expected should be incorporated
in the calculation of the O3 budget. Another important applica-
tion is related to the issue of the initiation of oxidation in high-
pressure CO2 fluids. It has been evidenced that oxidation in
hydrocarbon/O2/CO2 mixtures can be initiated by the primary
photoinduced production of odd-oxygen species under UV
irradiation.
-
1 27
is smaller than the sum of the heats of formation of O + O +
-
1 11
CO2 (494 kJ mol ). The heat of formation of CO3 is not
established. At any rate, a photoinduced reaction to produce
odd-oxygen species might be possible at least energetically up
to 281.6 nm.
On the other hand, a certain cage effect that lowers the
dissociation probability of O2 might not be negligible in high-
Acknowledgment. The present work was supported by a
Grant-in-Aid for Scientific Research (A) from the Ministry of
Education, Science and Culture of Japan (No. 12305051), which
is greatly appreciated.
29,30
pressure O2/CO2 mixtures. Troe and co-workers
studied I2
photodissociation in sub- and supercritical fluids. From their
results, the photolysis quantum yield of I2 is ca. 0.5 in 6 mol
-
3
-3
dm CO2. In our O2/CO2 system (0.78 mol dm O2, 9.22 mol
-
3
dm CO2), a similar effect is suggested to occur.
References and Notes
At present, however, we cannot estimate the contribution of
the two possible mechanisms quantitatively; one is the reaction
of O2 + CO2 to form O3 + CO or O + CO3, and the other is
the cage effect. Identification of products, measurements of the
dependence of the quantum yield on temperature and pressure,
and experiments with other third gases are desirable.
(
1) Koda, S.; Oshima, Y.; Otomo, J.; Ebukuro, T. Process Technol.
Proc. 1996, 12, 97.
(2) Koda, S.; Ebukuro, T.; Otomo, J.; Tsuruno, T.; Oshima, Y. J.
Photochem. Photobiol. A: Chem. 1998, 115, 7.
(3) Shardanand; Prasad Rao, A. D. J. Quant. Spectrosc. Radiat. Transfer
1
977, 17, 433.
(4) Shardanand J. Quant. Spectrosc. Radiat. Transfer 1977, 18, 525.
(5) Amoruso, A.; Crescentini, L. J. Quant. Spectrosc. Radiat. Transfer
(3) Atmospheric Implications. The atmospheric implications
1
1
1
995, 53, 457.
of excited O2 in the UV region has been discussed by previous
researchers,13 and they stated that O2(A) + O2 reactions
following O2 absorption contribute up to ca. 6% of total odd-
oxygen production at a height of around 50 km. Because they
assumed that the Herzberg band states in the UV region
dissociate independent of the wavelength, their evaluation is
suspected to be somewhat larger than the real contribution. The
present quantum yields as a function of wavelength indicate
that more accurate estimations of the relevance of absorption
of solar light by O2 under various conditions are necessary.
(6) Johnston, H. S.; Paige, M.; Yao, F. J. Geophys. Res. 1984, 89,
1661.
(7) Blake, A. J.; McCoy, D. G. J. Quant. Spectrosc. Radiat. Transfer
987, 38, 113.
(
(
8) Oshima, Y.; Okamoto, Y.; Koda, S. J. Phys. Chem. 1995, 99, 11830.
9) Bernath, P.; Carleer, M.; Fally, S.; Jenouvrier, A.; Vandaele, A.
C.; Hermans, C.; M e´ rienne, M.-F.; Colin, R. Chem. Phys. Lett. 1998, 297,
293.
(
10) Fally, S.; Vandaele, A. C.; Carleer, M.; Hermans, C.; Jenouvrier,
A.; M e´ rienne, M.-F.; Coquart, B.; Colin, R. J. Mol. Spectrosc. 2000, 204,
0.
(11) Pernot, C.; Durup, J.; Ozenne, J.-B.; Beswick, J. A.; Cosby, P. C.;
Moseley, J. T. J. Chem. Phys. 1979, 71, 2387.
12) Slanger, T. G.; Jusinski, L. E.; Black, G.; Gadd, G. E. Science 1988,
41, 945.
13) Shi, J.; Barker, J. R. J. Geophys. Res. 1992, 97, 13039.
(14) Huestis, D. L.; Copeland, R. A.; Knutsen, K.; Slanger, T. G. Can.
J. Phys. 1994, 72, 1109.
15) Copeland, R. A.; Knutsen, K.; Slanger, T. G. In Proceedings of
1
(4) Concluding Remarks. The wavelength dependence of
(
the quantum yield of primary odd-oxygen species was examined
as a function of the excitation wavelength. The quantum yield
showed different behaviors through ca. 242 nm, which corre-
sponds to the dissociation threshold of O2.
2
(
(
At wavelengths between 242 and 252 nm, the quantum yield
decreased monotonically with increasing laser wavelength in
both O2 and O2/CO2 mixtures. It became almost 0 at wave-
lengths greater than 252 nm. These findings could not be
explained by the contribution of the thermal energy of O2 in
the photodissociation process alone. One possible mechanism
that is consistent with the present finding is the thermal
dissociation of O2(A,A′,c) with the aid of thermal energy transfer
from O2(X) or CO2. However, it is not consistent with the
temperature dependence measured by Shi and Barker. Thermal
reaction of O2(A,A′,c) with O2 (or CO2) to produce O + O3
might be the most likely mechanism, which is strongly supported
by the experiment by Shi and Barker and also does not contradict
with the present results.
When the excitation wavelength was shorter than 242 nm,
the primary quantum yield was almost independent of the
wavelength. In pressurized O2 (2.0 MPa), the quantum yield
was ca. 2, and in pressurized O2/CO2 mixtures (9.6 MPa), it
was less than 2 even for the range of wavelengths below 242
nm. It has a tendency to increase with decreasing wavelength.
Solvent cage effect might be operative to some extent in
pressurized O2/CO2 mixtures (9.6 MPa).
the International Conference on Lasers ′93; Society for Optical and
Quantum Electronics: McLean, VA, 1994; p 318.
(16) Brown, L.; Vaida, V. J. Phys. Chem. 1996, 100, 7849.
(
17) Otomo, J.; Oshima, Y.; Takami, A.; Koda, S. J. Phys. Chem. A
000, 104, 3332.
18) Peng, D. Y.; Robinson, D. B. AIChE J. 1977, 23, 137.
2
(
(19) Liu, Z.-Y. AIChE J. 1998, 44, 1709.
(20) Molina, L. T.; Molina, M. J. J. Geophys. Res. 1986, 91, 14501.
(
21) Cooper, L. A.; Neill, P. J.; Wiesenfeld, J. R. J. Geophys. Res. 1993,
8, 12795.
22) DeMore, W. B.; Sander, S. P.; Howard, C. J.; Ravishankara, A.
9
(
R.; Golden, D. M.; Kolb, C. E.; Hampson, R. F.; Kurylo, M. J.; Molina,
M. J. Chemical Kinetics and Photochemical Data for Use in Stratospheric
Modeling; Evaluation No. 12, JPL Publication 97-4; Jet Propulsion
Laboratory: Pasadena, CA, 1997.
(23) Saxon, R. P.; Slanger, T. G. J. Geophys. Res. 1991, 96, 17291.
(24) Rogaski, C. A.; Price, J. M.; Mack, J. A.; Wodtke, A. M. Geophys.
Res. Lett. 1993, 20, 2885.
(
25) Miller, R. L.; Suits, A. G..; Houston, P. L.; Toumi, R.; Mack, J.
A.; Wodtke, A. M. Science 1994, 265, 1831.
26) Worrall, D. R.; Abdel-Shafi, A. A.; Wilkinson, F. J. Phys. Chem.
A 2001, 105, 1270.
27) Chase, M. W., Jr. NIST-JANAF Thermochemical Tables, 4th ed.;
(
(
J. Phys. Chem. Ref. Data Monograph No. 9; Joint publication of the
American Chemical Society and the American Institute of Physics for the
National Institute of Standards and Technology: New York, 1988; Parts I
and II.
(
28) Knutsen, K.; Dyer, M. J.; Copeland, R. A. J. Chem. Phys. 1994,
The present results would be useful for atmospheric modeling.
The production of odd-oxygen species at wavelengths longer
than 242.4 nm with the determined quantum yield in O2 where
1
01, 7415.
(
29) Otto, B.; Schroeder, J.; Troe, J. J. Chem. Phys. 1984, 81, 202.
(30) Troe, J. J. Phys. Chem. 1986, 90, 357.