OSA's Digital Library

Applied Optics

Applied Optics


  • Vol. 5, Iss. 8 — Aug. 1, 1966
  • pp: 1285–1291

On the Question of Equilibrium in Mercury + Thallium Iodide Arc Discharges

C. F. Gallo  »View Author Affiliations

Applied Optics, Vol. 5, Issue 8, pp. 1285-1291 (1966)

View Full Text Article

Enhanced HTML    Acrobat PDF (1244 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



Two aspects of the concept of local thermodynamic equilibrium are examined in medium-pressure, mercury arc discharges with thallium iodide additives. It is shown theoretically that the experimental intensity of the Tl 5350 Å line is reasonably consistent with a Boltzmann distribution of excited states. In fact, it is theoretically and experimentally shown that self-absorption is a major factor in limiting the intensity of the bright thallium 5350 Å line even though Ti is a minor constituent in the discharge and even though this line does not terminate on the ground state. The dramatic spectral inhomogeneity that develops in long, horizontal, ac discharges with excess TlI in the presence of a longitudinal temperature gradient is examined in detail. Both emission and absorption studies show that the spectral inhomogeneity is caused by a large gradient in the thallium concentration. This inhomogeneous distribution of TlI vapors is caused by an inhomogeneous and unsymmetrical distribution of condensed TlI along the tube walls which results from the temperature gradient. In turn, the temperature gradient is increased by the ionization of thallium which locally decreases the electrical resistivity, electric field, and power input to the arc. Thus, an equilibrium distribution of TlI vapors is attained only if the distribution of condensed TlI is reasonably uniform and the tube geometry and pressure are favorable for rapid diffusion of the vapors. The inhomogeneity also disappears if a sufficiently small quantity of solid TlI is added to the lamp so that it is all vaporized.

© 1966 Optical Society of America

Original Manuscript: February 14, 1966
Published: August 1, 1966

C. F. Gallo, "On the Question of Equilibrium in Mercury + Thallium Iodide Arc Discharges," Appl. Opt. 5, 1285-1291 (1966)

Sort:  Author  |  Year  |  Journal  |  Reset  


  1. W. Elenbaas, The High Pressure Mercury Vapour Discharge (Interscience, New York, 1951). See also, D. B. Gurevich, I. V. Podmonshenskii, Opt. Spectry. 15, 319 (1963).
  2. D. A. Larson, H. D. Fraser, W. V. Vushing, M. C. Unglert, Illum. Engr. 58, 434 (1963).
  3. G. H. Reiling, J. Opt. Soc. Am. 54, 532 (1964). [CrossRef]
  4. W. C. Gungle, F. Koury, J. F. Waymouth, J. Opt. Soc. Am. 54, 566 (1964); J. F. Waymouth, W. C. Gungle, J. M. Harris, F. Koury, Illum. Engr. 60, 85 (1965).
  5. E. C. Martt, L. J. Smialek, A. C. Green, Illum. Engr. 59, 34 (1964).
  6. T. H. Rautenberg, P. D. Johnson, Appl. Opt. 3, 487 (1964); P. D. Johnson, T. H. Rautenberg, J. Opt. Soc. Am. 54, 1425 (1964). [CrossRef]
  7. L. S. Frost, Westinghouse Research (private communication on unpublished studies of Hg + TlI lamps).
  8. C. F. Gallo (unpublished studies performed at the Westinghouse Research Laboratory).
  9. G. Cario, J. Frank, Z. Physik 17, 202 (1923); R. E. Swanson, R. H. McFarland, Phys. Rev. 98, 1063 (1955); R. A. Anderson, R. H. McFarland, Phys. Rev. 119, 693 (1960); E. K. Kraulinya, A. E. Lezdin, Yu. A. Silin, Opt. Spectry. 19, 84 (1965). [CrossRef]
  10. J. A. McInally, Xerox Research (private communication) and 18th Gaseous Electronics Conference, Minneapolis, Minnesota, Oct. 1965.
  11. G. H. Reiling, Inst. Radio Engrs. Trans. Electron Devices9, 271 (1962) and (private communication). [CrossRef]
  12. A. V. Phelps, Westinghouse Research (private communication).
  13. C. Corliss, W. Bozman, Experimental Transition Probabilities for Spectral Lines of Seventy Elements (Government Printing Office, Washington, D. C., 1962), Natl. Bur. Std. Monogr. 53.
  14. T. Holstein, Phys. Rev. 83, 1159 (1951). [CrossRef]
  15. T. Holstein, Phys. Rev. 72, 1212 (1947). [CrossRef]
  16. A. C. G. Mitchell, M. W. Zemansky, Resonance Radiation and Excited Atoms (Cambridge University Press, Cambridge, England, 1934).
  17. S. Chen, M. Takeo, Rev. Mod. Phys. 29, 20 (1957). [CrossRef]
  18. Reference 17, Table 3.
  19. W. Furssov, A. Vlassov, Phys. Zeits. Sowjetunion 10, 378 (1936). This reference was taken from Ref. 15, Eq. (5.17).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


Fig. 1 Fig. 2 Fig. 3
Fig. 4 Fig. 5

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited