Abstract

The light emitted from an electron-irradiated self-supported foil (334±30 Å) of evaporated carbon has been investigated experimentally. Normally incident, 1-μA electron beams having monochromatic energies of 297, 423, 632 keV and 1.10 MeV were used. These correspond to β2 values of 0.6, 0.7, 0.8, and 0.9, respectively, where β = ν/c, and ν is the velocity of the incident electrons. The absolute photon intensity emitted in the 2200–5800-Å spectral region was measured with a calibrated optical system. The results were analyzed with respect to wavelength of emitted radiation, forward angle of emission, θ (15° and 30°), and degree of polarization (parallel and perpendicular to the plane of the incident electrons and observed light). The transition-radiation contribution determined from the parallel-polarized component has been compared with the generalized theory of Ritchie and Eldridge, using the optical constants of graphite and glassy carbon. From this comparison and a best-fit calculation, the optical constants for the carbon film throughout the 2200–5800-Å spectral region have been derived. The derived constants indicate that the carbon film has optical properties between those of graphite and glassy (amorphous) carbon. The results obtained stress the importance of measuring the optical constants of a given carbon film for any experiment in which they are needed.

© 1971 Optical Society of America

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References

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  1. I. M. Frank and V. L. Ginzburg, J. Phys. (USSR) 9, 353 (1945).
  2. R. H. Ritchie and H. B. Eldridge, Phys. Rev. 126, 1935 (1962).
    [Crossref]
  3. D. E. Bradley, Brit. J. Appl. Phys. 5, 65 (1954).
    [Crossref]
  4. E. A. Taft and H. R. Philipp, Phys. Rev. 138, A197 (1965).
    [Crossref]
  5. Optical constants for the glassy carbon were kindly supplied by H. R. Philipp; they did not appear in Ref. 4.
  6. A. Cosslett and V. E. Cosslett, Brit. J. Appl. Phys. 8, 374 (1957).
    [Crossref]

1965 (1)

E. A. Taft and H. R. Philipp, Phys. Rev. 138, A197 (1965).
[Crossref]

1962 (1)

R. H. Ritchie and H. B. Eldridge, Phys. Rev. 126, 1935 (1962).
[Crossref]

1957 (1)

A. Cosslett and V. E. Cosslett, Brit. J. Appl. Phys. 8, 374 (1957).
[Crossref]

1954 (1)

D. E. Bradley, Brit. J. Appl. Phys. 5, 65 (1954).
[Crossref]

1945 (1)

I. M. Frank and V. L. Ginzburg, J. Phys. (USSR) 9, 353 (1945).

Bradley, D. E.

D. E. Bradley, Brit. J. Appl. Phys. 5, 65 (1954).
[Crossref]

Cosslett, A.

A. Cosslett and V. E. Cosslett, Brit. J. Appl. Phys. 8, 374 (1957).
[Crossref]

Cosslett, V. E.

A. Cosslett and V. E. Cosslett, Brit. J. Appl. Phys. 8, 374 (1957).
[Crossref]

Eldridge, H. B.

R. H. Ritchie and H. B. Eldridge, Phys. Rev. 126, 1935 (1962).
[Crossref]

Frank, I. M.

I. M. Frank and V. L. Ginzburg, J. Phys. (USSR) 9, 353 (1945).

Ginzburg, V. L.

I. M. Frank and V. L. Ginzburg, J. Phys. (USSR) 9, 353 (1945).

Philipp, H. R.

E. A. Taft and H. R. Philipp, Phys. Rev. 138, A197 (1965).
[Crossref]

Ritchie, R. H.

R. H. Ritchie and H. B. Eldridge, Phys. Rev. 126, 1935 (1962).
[Crossref]

Taft, E. A.

E. A. Taft and H. R. Philipp, Phys. Rev. 138, A197 (1965).
[Crossref]

Brit. J. Appl. Phys. (2)

D. E. Bradley, Brit. J. Appl. Phys. 5, 65 (1954).
[Crossref]

A. Cosslett and V. E. Cosslett, Brit. J. Appl. Phys. 8, 374 (1957).
[Crossref]

J. Phys. (USSR) (1)

I. M. Frank and V. L. Ginzburg, J. Phys. (USSR) 9, 353 (1945).

Phys. Rev. (2)

R. H. Ritchie and H. B. Eldridge, Phys. Rev. 126, 1935 (1962).
[Crossref]

E. A. Taft and H. R. Philipp, Phys. Rev. 138, A197 (1965).
[Crossref]

Other (1)

Optical constants for the glassy carbon were kindly supplied by H. R. Philipp; they did not appear in Ref. 4.

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Figures (6)

Fig. 1
Fig. 1

Transition-radiation dependence upon optical constants for a self-supported 334-Å carbon foil. Exp. (||–⊥) represents the net flux in the parallel plane after subtraction of bremsstrahlung. B.F. represents the best fit to the experimental data, based on the theory of Ritchie and Eldridge for θ=30° and β2=0.8 (632 keV).

Fig. 2
Fig. 2

Transition-radiation dependence upon optical constants for self-supported 334-Å carbon foil. Exp. (||–⊥) and B.F. have the same meaning as in Fig. 1. θ= 15° and β2=0.9 (1.1 MeV).

Fig. 3
Fig. 3

Comparison of optical constants for glassy carbon, graphite, and for the evaporated carbon foil used in this experiment. ng,kg—graphite,4 nc,kc—glassy carbon,5 nT.R.,kT.R.—this experiment.

Fig. 4
Fig. 4

Spectral distribution of parallel- and perpendicular-polarized light emitted from a 334-Å carbon foil. θ=15°, β2=0.9 (1.1 MeV). R and E theory refers to Ref. 2 calculated with the best-fit optical constants.

Fig. 5
Fig. 5

Spectral distribution of parallel-polarized light emitted from a 334-Å carbon foil. The perpendicular-polarized component was negligible. R and E theory has the same meaning as in Fig. 4, θ=30° and β2=0.8 (632 keV).

Fig. 6
Fig. 6

Dependence of emitted flux upon β2(=ν/c)2, at a wavelength of 4130 Å and θ=30°. β2 values of 0.6, 0.7, 0.8, and 0.9 correspond to incident electron energies of 297, 423, 632 keV and 1.1 MeV, respectively.

Tables (1)

Tables Icon

Table I Best-fit optical constants of carbon foil, determined by fitting the observed transition radiation to the Ritchie and Eldridge theory.