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Laser‐induced dissociation of ozone and resonance fluorescence of OH in ambient air
1.H. Niki, E. E. Daby, and B. Weinstock, Adv. Chem. Ser. 113, 16 (1972);
1.K. L. Demerjian, J. A. Kerr, and J. G. C. Calvert, Adv. Sci. Tech. 4, 1 (1974).
2.See, for example, in Proceedings of the Third Conference on CIAP, edited by A. J. Broderick and T. M. Harol (U.S. Government Department of Transportation, Washington, D.C., 1974), particularly the reports by Chung and Johnston (p. 323), Whitten, Boruki, and Turco (p. 342), Wofsy (p. 359).
3.C. C. Wang and L. I. Davis, Phys. Rev. Lett. 32, 349 (1974).
4.As discussed in Ref. 3, the observed fluorescence near 3090 Å is that emitted by a thermalized distribution of excited OH. This is different from the fluorescence emitted by nonequilibrium distribution of excited OH investigated by I. Tanaka, T. Carrington, and H. P. Broida, J. Chem. Phys. 35, 750 (1961);
4.it is also different from single rotational‐electronic transitions such as the line near 3072 Å investigated by T. Hollander and H. P. Broida, J. Quant. Spectrosc. Radiat. Transfer 7, 965 (1967). Note also that the excitation procedure outlined in the text precludes the possibility that the OH concentration deduced from our measurements is an artificat due to Raman scattering of methane and other hydrocarbons in air (Ref. 3), or due to other resonant or nonresonant processes.
5.For a detailed description of these measurements, see C. C. Wang, L. I. Davis, Jr., C. H. Wu, S. Japar, H. Niki, and B. Weinstock, Science 189, 797 (1975), and references cited therein.
6.E. C. Y. Inn and Y. Tanaka, J. Opt. Soc. Am. 43, 870 (1953).
7.J. R. NcNesby and H. Okabe, in Advances in Photochemistry, Vol. 3, edited by W. A. Noyes, Jr., G. S. Hammond, and J. N. Pitts, Jr. (Wiley, New York, 1964), p. 157.
8.In Ref. 3, the failure to observe any ozone dependence inside the laboratory apparently resulted from the fact that insufficient concentrations of ozone were generated in the focal region. However, the conclusions therein remain correct as the observed OH fluorescence was found to be linearly dependent on the intensity of excitation.
9.The phenomenon of laser‐induced dissociation of ozone can also be used as a means for detecting ambient ozone. The detection limit will be determined by the background OH signal and by the process of two‐photon dissociation of water, but a detectability of less than (0.25 ppb) should be easily realizable. This technique may prove to be valuable for in situ measurements requiring high spatial resolution. For a description of other methods for atmospheric ozone measurements, see, for example, A. E. S. Green, The Middle Ultraviolet: Its Science and Technology (Wiley, New York, 1966), p. 93.
10.C. C. Wang and L. I. Davis, J. Chem. Phys. 62, 53 (1975).
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