Ionization of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">H</mi><mn></mn><mo>(</mo><mn>1</mn><mi>s</mi><mo>)</mo><mn></mn></math></span> near Threshold

J. William McGowan; E. M. Clarke

doi:10.1103/PhysRev.167.43

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Ionization of $H (1 s)$ near Threshold

J. William McGowan^* and E. M. Clarke^†

Gulf General Atomic Incorporated, John Jay Hopkins Laboratory for Pure and Applied Science, San Diego, California 92112

^*1965-1966 Visiting Fellow, Joint Institute for Laboratory Astrophysics, University of Colorado, Boulder, Colo.
^†Present address: Physics Department, St. Francis Xavier University, Antigonish, N. S.

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Phys. Rev. 167, 43 – Published 5 March, 1968

DOI: https://doi.org/10.1103/PhysRev.167.43

Abstract

An experimental study of the threshold of ionization of H ( $1 s$ ) has been made. The electron-impact spectrometer used has an electron-energy resolution ≲0.06 eV. For atomic hydrogen, it has been demonstrated that for ∼0.4 eV above threshold, the cross section for ionization is a nonlinear and complicated function of the electron energy. The form of the cross section approaches a ${(E_{e} - I P)}^{1.13 \pm 0.03}$ power law, although within 0.05 eV of threshold a higher power law would be consistent with our data. Above 0.4 eV and for somewhat less than 3 eV, a linear law more accurately describes our result. The slope of the linear portion of the cross section is in good agreement with other experiments, but in disagreement with theory. The intercept of the linear extrapolation of the straight-line portion with the energy axis is 0.032±0.005 eV above threshold.

References (29)

J. Wm. McGowan and M. A. Fineman, in Proceedings of the Fourth International Conference on the Physics of Electronic and Atomic Collisions, Quebec, 1965, edited by L. Kerwin and W. Fite (Science Book Crafters, Hastings-on-Hudson, New York, 1965), p. 429
(a) J. Wm. McGowan, M. A. Fineman, E. M. Clarke, and H. P. Hanson, following paper, Phys. Rev. 167, 52 (1968) (b) J. W. McGowan and M. A. Fineman, Phys. Rev. Letters 15, 179 (1965)
M. R. H. Rudge and M. J. Seaton, Proc. Roy. Soc. (London) A213, 262 (1965) ibid.83, 680 (1964) M. R. H. Rudge and S. B. Schwartz, ibid. 88, 579 (1966)
S. Geltman, Phys. Rev. 102, 171 (1956)
R. K. Peterkop, Izv. Akad. Nauk. Latv. S.S.R. 9, 79 (1960) ibid.27, 1012 (1963) Proc. Phys. Soc. (London) A77, 1220 (1961) Zh. Eksperim. i Teor. Fiz. 41, 1938 (1962) ibid.43, 616 (1962) [English transls.: Soviet Phys.—JETP 14, 1377 (1962) Soviet Phys.—JETP 16, 442 (1963)] R. K. PeterkopOpt. i Spektroskopiya 13, 153 (1962) [English transl.: Opt. Spectry. 13, 87 (1962)]
G. H. Wannier, Phys. Rev. 90, 817 (1953)
K. Omidvar, Phys. Rev. 140, A26 (1965)
A. Temkin, Phys. Rev. Letters 16, 835 (1966)
K. Omidvar, Phys. Rev. Letters 18, 153 (1967)
W. L. Fite and R. T. Brackmann, Phys. Rev. 112, 1141 (1958)
A. Boksenburg, thesis, University College, London, 1960 (unpublished) L. F. Kieffer, JILA Report No. 30, 1965 (unpublished)
E. W. Rothe, L. L. Marion, R. H. Neynaber, and S. M. Trujillo, Phys. Rev. 125, 582 (1962)
J. Wm. McGowan, E. M. Clarke, H. P. Hanson, and R. F. Stebbings, Phys. Rev. Letters 13, 620 (1964)
J. Wm. McGowan, E. M. Clarke, and E. K. Curley, Phys. Rev. Letters 15, 917 (1965) ibid.17, 66E (1966)
J. Wm. McGowan, Phys. Rev. Letters 17, 1207 (1966) Phys. Rev. 156, 165 (1967)
J. Wm. McGowan (unpublished)
B. R. Turner, M. A. Fineman, and R. F. Stebbings, J. Chem. Phys. 42, 4088 (1965)
P. Marmet and L. Kerwin, Can. J. Phys. 38, 787 (1960) C. E. Brion, J. Chem. Phys. 40, 2995 (1965) G. J. Schulz, Phys. Rev. 125, 299 (1962)
J. Wm. McGowan, Rev. Sci. Instr. 38, 285 (1967)
Omitted endnote
H. P. Hanson and Dr. R. Pohler (unpublished) R. F. Stebbings, J. Wm. McGowan, and R. A. Young, NASA Report NAS 59110, 1966 (unpublished)
W. E. Lamb and R. C. Rutherford, Phys. Rev. 79, 549 (1950) R. F. Stebbings, W. L. Fite, D. G. Hummer, and R. T. Brackmann, ibid. 119, 1939 (1960)
K. R. Spangenberg, Vacuum Tubes (McGraw-Hill Book Company, Inc., New York, 1948)
Charlotte E. Moore, Atomic Energy Levels, Natl. Bur. Std. (U.S.) Circ. No. 467 (U. S. Government Printing Office, Washington, D. C., 1949), Vol. 1
Omitted endnote
personal communication, O. Bely
J. Wm. McGowan, Phys. Rev. 156, 165 (1967)
Unpublished measurements C. E. Brion and G. E. Thomas
I. Vinkalns and M. Gailitis, in Proceedings of the Fifth International Conference on the Physics of Electronic and Atomic Collisions, Leningrad, U.S.S.R., 1967, p. 648 (unpublished) Collisions of Electrons with Atoms (The Physics Institute of the Latvian Academy of Sciences, Rega, 1967), Vol. IV, p. 17

[c1] J. Wm. McGowan and M. A. Fineman, in Proceedings of the Fourth International Conference on the Physics of Electronic and Atomic Collisions, Quebec, 1965, edited by L. Kerwin and W. Fite (Science Book Crafters, Hastings-on-Hudson, New York, 1965), p. 429

[c2] (a) J. Wm. McGowan, M. A. Fineman, E. M. Clarke, and H. P. Hanson, following paper, Phys. Rev. 167, 52 (1968) (b) J. W. McGowan and M. A. Fineman, Phys. Rev. Letters 15, 179 (1965)

[c3] M. R. H. Rudge and M. J. Seaton, Proc. Roy. Soc. (London) A213, 262 (1965) ibid.83, 680 (1964) M. R. H. Rudge and S. B. Schwartz, ibid. 88, 579 (1966)

[c4] S. Geltman, Phys. Rev. 102, 171 (1956)

[c5] R. K. Peterkop, Izv. Akad. Nauk. Latv. S.S.R. 9, 79 (1960) ibid.27, 1012 (1963) Proc. Phys. Soc. (London) A77, 1220 (1961) Zh. Eksperim. i Teor. Fiz. 41, 1938 (1962) ibid.43, 616 (1962) [English transls.: Soviet Phys.—JETP 14, 1377 (1962) Soviet Phys.—JETP 16, 442 (1963)] R. K. PeterkopOpt. i Spektroskopiya 13, 153 (1962) [English transl.: Opt. Spectry. 13, 87 (1962)]

[c6] G. H. Wannier, Phys. Rev. 90, 817 (1953)

[c7] K. Omidvar, Phys. Rev. 140, A26 (1965)

[c8] A. Temkin, Phys. Rev. Letters 16, 835 (1966)

[c9] K. Omidvar, Phys. Rev. Letters 18, 153 (1967)

[c10] W. L. Fite and R. T. Brackmann, Phys. Rev. 112, 1141 (1958)

[c11] A. Boksenburg, thesis, University College, London, 1960 (unpublished) L. F. Kieffer, JILA Report No. 30, 1965 (unpublished)

[c12] E. W. Rothe, L. L. Marion, R. H. Neynaber, and S. M. Trujillo, Phys. Rev. 125, 582 (1962)

[c13] J. Wm. McGowan, E. M. Clarke, H. P. Hanson, and R. F. Stebbings, Phys. Rev. Letters 13, 620 (1964)

[c14] J. Wm. McGowan, E. M. Clarke, and E. K. Curley, Phys. Rev. Letters 15, 917 (1965) ibid.17, 66E (1966)

[c15] J. Wm. McGowan, Phys. Rev. Letters 17, 1207 (1966) Phys. Rev. 156, 165 (1967)

[c16] J. Wm. McGowan (unpublished)

[c17] B. R. Turner, M. A. Fineman, and R. F. Stebbings, J. Chem. Phys. 42, 4088 (1965)

[c18] P. Marmet and L. Kerwin, Can. J. Phys. 38, 787 (1960) C. E. Brion, J. Chem. Phys. 40, 2995 (1965) G. J. Schulz, Phys. Rev. 125, 299 (1962)

[c19] J. Wm. McGowan, Rev. Sci. Instr. 38, 285 (1967)

[c20] Omitted endnote

[c21] H. P. Hanson and Dr. R. Pohler (unpublished) R. F. Stebbings, J. Wm. McGowan, and R. A. Young, NASA Report NAS 59110, 1966 (unpublished)

[c22] W. E. Lamb and R. C. Rutherford, Phys. Rev. 79, 549 (1950) R. F. Stebbings, W. L. Fite, D. G. Hummer, and R. T. Brackmann, ibid. 119, 1939 (1960)

[c23] K. R. Spangenberg, Vacuum Tubes (McGraw-Hill Book Company, Inc., New York, 1948)

[c24] Charlotte E. Moore, Atomic Energy Levels, Natl. Bur. Std. (U.S.) Circ. No. 467 (U. S. Government Printing Office, Washington, D. C., 1949), Vol. 1

[c25] Omitted endnote

[c26] personal communication, O. Bely

[c27] J. Wm. McGowan, Phys. Rev. 156, 165 (1967)

[c28] Unpublished measurements C. E. Brion and G. E. Thomas

[c29] I. Vinkalns and M. Gailitis, in Proceedings of the Fifth International Conference on the Physics of Electronic and Atomic Collisions, Leningrad, U.S.S.R., 1967, p. 648 (unpublished) Collisions of Electrons with Atoms (The Physics Institute of the Latvian Academy of Sciences, Rega, 1967), Vol. IV, p. 17

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Ionization of $H (1 s)$ near Threshold

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Ionization of H(1s) near Threshold

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Ionization of $H (1 s)$ near Threshold