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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 28, Iss. 6 — Mar. 15, 1989
  • pp: 1206–1213

Photochemical effects in 243-nm two-photon excitation of atomic hydrogen in flames

J. E. M. Goldsmith  »View Author Affiliations


Applied Optics, Vol. 28, Issue 6, pp. 1206-1213 (1989)
http://dx.doi.org/10.1364/AO.28.001206


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Abstract

This paper describes photochemical effects observed during two-photon 1S–2S excitation of atomic hydrogen in flames using 243-nm laser radiation. An I4 intensity dependence is observed in regions of the flame where the natural atomic concentration is low, suggesting an I2 photochemical production mechanism, which we believe is due to two-photon excitation of water molecules, which then predissociate to form H and OH fragments. In a measurement of OH created in the flame by the 243-nm beam, we observe the same I2 intensity dependence with the laser detuned from the atomic hydrogen 1S–2S resonance, but an apparent I3,4 dependence is observed when the laser is tuned to the resonance. We believe that a second photochemical mechanism contributes at the resonance, namely, two-photon excitation of H, followed by collisional energy transfer to water molecules, which then fall apart into H and OH fragments. We model this process and show that a combination of I2 and I4 dependences can lead to an intensity dependence that mimics a single I3,4 dependence over a limited range of intensities.

© 1989 Optical Society of America

History
Original Manuscript: September 20, 1988
Published: March 15, 1989

Citation
J. E. M. Goldsmith, "Photochemical effects in 243-nm two-photon excitation of atomic hydrogen in flames," Appl. Opt. 28, 1206-1213 (1989)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-28-6-1206


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References

  1. J. E. M. Goldsmith, “Multiphoton Excitation Techniques for Combustion Diagnostics,” AIP Conf. Proc. 146, 279 (1986), and references therein. [CrossRef]
  2. A. W. Miziolek, M. A. DeWilde, “Multiphoton Photochemical and Collisional Effects During Oxygen-Atom Flame Detection,” Opt. Lett. 9, 390 (1984). [CrossRef] [PubMed]
  3. J. E. M. Goldsmith, “Photochemical Effects in Two-Photon-Excited Fluorescence Detection of Atomic Oxygen in Flames,” Appl. Opt. 26, 3566 (1987). [CrossRef] [PubMed]
  4. J. E. M. Goldsmith, “Photochemical Effects in 205-nm, Two-Photon-Excited Fluorescence Detection of Atomic Hydrogen in Flames,” Opt. Lett. 11, 416 (1986). [CrossRef] [PubMed]
  5. J. E. M. Goldsmith, “Flame Studies of Atomic Hydrogen and Oxygen Using Resonant Multiphoton Optogalvanic Spectroscopy,” in Twentieth Symposium (International) on Combustion (Combustion Institute, Pittsburgh, PA, 1984), pp. 1331–1337.
  6. J. E. M. Goldsmith, “Two-Step Saturated Fluorescence Detection of Atomic Hydrogen in Flames,” Opt. Lett. 10, 116 (1985). [CrossRef] [PubMed]
  7. This burner was purchased from McKenna Products, Pittsburg, CA 94565.
  8. C. Fotakis, C. B. McKendrick, R. J. Donovan, “Two-Photon Excitation of H2O and D2O with a KrF Laser (248 nm): Photofragment Fluorescence from OH and OD (A2Σ+)”, Chem. Phys. Lett. 80, 598 (1981). [CrossRef]
  9. A. Hodgson, J. P. Simons, M. N. R. Ashfold, J. M. Bayley, R.N. Dixon, “Quantum-State-Selected Photodissociation of H2O (C‾1B1),” Chem. Phys. Lett. 107, 1 (1984). [CrossRef]
  10. G. Meijer, J. J. ter Meulen, P. Andresen, A. Bath, “Sensitive Quantum State Selective Detection of H2O and D2O by (2+1)-Resonance Enhanced Multiphoton Ionization,” J. Chem. Phys. 85, 6914 (1986). [CrossRef]
  11. I. Tanaka, T. Carrington, H. P. Broida, “Photon-Dissociation of Water: Initial Nonequilibrium Populations of Rotational States of OH(2Σ+),” J. Chem. Phys. 35, 750 (1961);T. Carrington, “Angular Momentum Distribution and Emission Spectrum of OH (2Σ+) in the Photodissociation of H2O,” J. Chem. Phys. 41, 2012 (1964). [CrossRef]
  12. J. E. M. Goldsmith, “Multiphoton-Excited Fluorescence Measurements of Atomic Hydrogen in Low-Pressure Flames,” in Twenty-Second Symposium (International) on Combustion (Combustion Institute, Pittsburgh, PA, 1988), in press.
  13. S. J. Harris, A. M. Weiner, R. J. Blint, J. E. M. Goldsmith, “Concentration Profiles in Rich and Sooting Ethylene Flames,” in Twenty-First Symposium (International) on Combustion (Combustion Institute, Pittsburgh, PA, 1986), pp. 1033–1045.

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