Abstract

The differential Raman cross sections of the main Raman-active vibrations have been measured in the gases N<sub>2</sub>, O<sub>2</sub>, H<sub>2</sub>, CO, NO, CO<sub>2</sub>, SO<sub>2</sub>, N<sub>2</sub>O, H<sub>2</sub>S, NH<sub>3</sub>, ND<sub>3</sub>, CH<sub>4</sub>, C<sub>2</sub>H<sub>6</sub>, and C<sub>6</sub>H<sub>6</sub> using 488.0-nm laser light. The present results are compared with previous measurements made at other wavelengths. The Raman cross sections of the rotational lines in the diatomic gases were also measured, as were the vibrational-rotational lines of O<sub>2</sub> and N<sub>2</sub>. Absolute measurement of the Raman cross sections were performed two ways: (i) by calibrating the Raman spectrometer, and (ii) by comparing the unknown against liquid benzene (for which the Raman cross section has been measured). Results of these measurements compare reasonably well with previous determinations for which corrections for the υ<sup>4</sup> frequency dependence were made.

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  1. E. J. Stansbiiry, M. F. Crawford, and H. L. Welch, Can. J. Phys. 31, 954 (1953).
  2. W. F. Murphy, W. Holzer, and H. J. Bernstein, Appl. Spectrosc. 23, 211 (1969).
  3. D. G. Fouche and R. K. Chang, Appl. Phys. Letters 18, 579 (1971).
  4. D. G. Fouche and R. K. Chang, Appl. Phys. Letters 20, 256 (1972).
  5. C. M. Penney, L. M. Goldman, and M. Lapp, Nature Phys. Sci. 235, 110 (1972).
  6. The collection factor Fc is defined for the particular scattering geometry of laser Raman spectrometer, in which the spatial width of the object, i.e., the Raman scattered light from the scattering volume, is finite and small. When the entrance slits are wide compared to the spatial width of the object and the spectral bandwidth of the spectrometer is wider than the natural linewidth of the Raman scattered light, then Fc≃1. When the slits are narrow, then Fc is the ratio of the integrated intensity of the measured Raman line to the integrated area of the same line measured with wide slits. Integrated intensity is used here as the measured area of the Raman line divided by the spectral slit width.
  7. W. Holzer, W. F. Murphy, and H. J. Bernstein, J. Chem. Phys. 52, 399 (1970).
  8. K. Sakurai and H. P. Broida, J. Chem. Phys. 50, 2404 (1969).
  9. G. Herzberg, Molecular Spectra and Molecular Structure, I. Spectra of Diatomnic Molecules, 2nd ed. (Van Nostrand Reinhold, New York, 1950), p. 128.
  10. The differential Rayleigh cross section for incident polarized laser light and orthogonal scattering geometry was computed from the equations (dσ/dΩ)Ray= (3/8π)σtot, where σtot= 128π5α2/3λ4 and α = n2-1/4πNn - ½πN. α is the polarizability, n the index of refraction, N the number density of gas molecules, λ the wavelength, and σtot the integrated (total) Rayleigh scattering cross section per molecule, assuming no depolarization. Corrections for finite depolarization are small. Explanation of Rayleigh scattering is given in the standard text: S. Chandrasekhar, Radiative Transfer (Dover, New York, 1960), p. 35.
  11. Indices of refraction were computed from the dispersion relationships for each of the gases considered here. Sources for dispersion equations and indices are E. R. Peck and B. N. Khanna, J. Opt. Soc. Am. 56, 1059 (1966); C. W. Allen, Astrophysical Quantities (Athens Press, New York, 1963), p. 87; Landolt-Bornstein (Springer, Berlin, 1950), Table 1, p. 401; International Critical Tables (McGraw-Hill, New York, 1930), Vol. 7, pp. 1–11.
  12. Yoshiaki Kato and Hiroski Takuma, J. Opt. Soc. Am. 61, 347 (1971).

Bernstein, H. J.

W. Holzer, W. F. Murphy, and H. J. Bernstein, J. Chem. Phys. 52, 399 (1970).

W. F. Murphy, W. Holzer, and H. J. Bernstein, Appl. Spectrosc. 23, 211 (1969).

Broida, H. P.

K. Sakurai and H. P. Broida, J. Chem. Phys. 50, 2404 (1969).

Chang, R. K.

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 20, 256 (1972).

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 18, 579 (1971).

Crawford, M. F.

E. J. Stansbiiry, M. F. Crawford, and H. L. Welch, Can. J. Phys. 31, 954 (1953).

Fouche, D. G.

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 18, 579 (1971).

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 20, 256 (1972).

Goldman, L. M.

C. M. Penney, L. M. Goldman, and M. Lapp, Nature Phys. Sci. 235, 110 (1972).

Herzberg, G.

G. Herzberg, Molecular Spectra and Molecular Structure, I. Spectra of Diatomnic Molecules, 2nd ed. (Van Nostrand Reinhold, New York, 1950), p. 128.

Holzer, W.

W. F. Murphy, W. Holzer, and H. J. Bernstein, Appl. Spectrosc. 23, 211 (1969).

W. Holzer, W. F. Murphy, and H. J. Bernstein, J. Chem. Phys. 52, 399 (1970).

Kato, Yoshiaki

Yoshiaki Kato and Hiroski Takuma, J. Opt. Soc. Am. 61, 347 (1971).

Khanna, B. N.

Indices of refraction were computed from the dispersion relationships for each of the gases considered here. Sources for dispersion equations and indices are E. R. Peck and B. N. Khanna, J. Opt. Soc. Am. 56, 1059 (1966); C. W. Allen, Astrophysical Quantities (Athens Press, New York, 1963), p. 87; Landolt-Bornstein (Springer, Berlin, 1950), Table 1, p. 401; International Critical Tables (McGraw-Hill, New York, 1930), Vol. 7, pp. 1–11.

Lapp, M.

C. M. Penney, L. M. Goldman, and M. Lapp, Nature Phys. Sci. 235, 110 (1972).

Murphy, W. F.

W. F. Murphy, W. Holzer, and H. J. Bernstein, Appl. Spectrosc. 23, 211 (1969).

W. Holzer, W. F. Murphy, and H. J. Bernstein, J. Chem. Phys. 52, 399 (1970).

Peck, E. R.

Indices of refraction were computed from the dispersion relationships for each of the gases considered here. Sources for dispersion equations and indices are E. R. Peck and B. N. Khanna, J. Opt. Soc. Am. 56, 1059 (1966); C. W. Allen, Astrophysical Quantities (Athens Press, New York, 1963), p. 87; Landolt-Bornstein (Springer, Berlin, 1950), Table 1, p. 401; International Critical Tables (McGraw-Hill, New York, 1930), Vol. 7, pp. 1–11.

Penney, C. M.

C. M. Penney, L. M. Goldman, and M. Lapp, Nature Phys. Sci. 235, 110 (1972).

Sakurai, K.

K. Sakurai and H. P. Broida, J. Chem. Phys. 50, 2404 (1969).

Stansbiiry, E. J.

E. J. Stansbiiry, M. F. Crawford, and H. L. Welch, Can. J. Phys. 31, 954 (1953).

Takuma, Hiroski

Yoshiaki Kato and Hiroski Takuma, J. Opt. Soc. Am. 61, 347 (1971).

Welch, H. L.

E. J. Stansbiiry, M. F. Crawford, and H. L. Welch, Can. J. Phys. 31, 954 (1953).

Other (12)

E. J. Stansbiiry, M. F. Crawford, and H. L. Welch, Can. J. Phys. 31, 954 (1953).

W. F. Murphy, W. Holzer, and H. J. Bernstein, Appl. Spectrosc. 23, 211 (1969).

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 18, 579 (1971).

D. G. Fouche and R. K. Chang, Appl. Phys. Letters 20, 256 (1972).

C. M. Penney, L. M. Goldman, and M. Lapp, Nature Phys. Sci. 235, 110 (1972).

The collection factor Fc is defined for the particular scattering geometry of laser Raman spectrometer, in which the spatial width of the object, i.e., the Raman scattered light from the scattering volume, is finite and small. When the entrance slits are wide compared to the spatial width of the object and the spectral bandwidth of the spectrometer is wider than the natural linewidth of the Raman scattered light, then Fc≃1. When the slits are narrow, then Fc is the ratio of the integrated intensity of the measured Raman line to the integrated area of the same line measured with wide slits. Integrated intensity is used here as the measured area of the Raman line divided by the spectral slit width.

W. Holzer, W. F. Murphy, and H. J. Bernstein, J. Chem. Phys. 52, 399 (1970).

K. Sakurai and H. P. Broida, J. Chem. Phys. 50, 2404 (1969).

G. Herzberg, Molecular Spectra and Molecular Structure, I. Spectra of Diatomnic Molecules, 2nd ed. (Van Nostrand Reinhold, New York, 1950), p. 128.

The differential Rayleigh cross section for incident polarized laser light and orthogonal scattering geometry was computed from the equations (dσ/dΩ)Ray= (3/8π)σtot, where σtot= 128π5α2/3λ4 and α = n2-1/4πNn - ½πN. α is the polarizability, n the index of refraction, N the number density of gas molecules, λ the wavelength, and σtot the integrated (total) Rayleigh scattering cross section per molecule, assuming no depolarization. Corrections for finite depolarization are small. Explanation of Rayleigh scattering is given in the standard text: S. Chandrasekhar, Radiative Transfer (Dover, New York, 1960), p. 35.

Indices of refraction were computed from the dispersion relationships for each of the gases considered here. Sources for dispersion equations and indices are E. R. Peck and B. N. Khanna, J. Opt. Soc. Am. 56, 1059 (1966); C. W. Allen, Astrophysical Quantities (Athens Press, New York, 1963), p. 87; Landolt-Bornstein (Springer, Berlin, 1950), Table 1, p. 401; International Critical Tables (McGraw-Hill, New York, 1930), Vol. 7, pp. 1–11.

Yoshiaki Kato and Hiroski Takuma, J. Opt. Soc. Am. 61, 347 (1971).

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