Abstract

The infrared reflectance of water at incidence angles of 70° and 75° has been measured in the spectral region between 2 and 25 μm. We have used the measured reflectances of polarized radiant flux to determine the real part of the refractive index from the Fresnel equations. The imaginary part of the refractive index can be accurately determined from reflection measurements alone only in regions of strong absorption; in other regions we have used values based on measurements of transmittance. We give values of the optical constants in tabular form and compare them with recent determinations by other investigators.

© 1969 Optical Society of America

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References

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  1. W. M. Irvine and J. B. Pollack, Icarus 8, 324 (1968).
    [Crossref]
  2. M. Centano. J. Opt. Soc. Am. 31, 244 (1941).
    [Crossref]
  3. E. N. Dorsey, Properties of Ordinary Water Substance (Rheinhold Publ. Co., New York, 1940).
  4. C. H. Cartwright, Nature 135, 872 (1935).
    [Crossref]
  5. L. D. Kislovskii, Opt. Spectry 7, 201 (1959).
  6. E. D. McAlister (private communication) indicates that his reflection spectra were obtained with a nonparallel unpolarized beam and that no measurements of spectrograph discrimination were made.
  7. L. Pontier and C. Dechambenov, Ann. Geophys. 21, 462 (1965);Ann. Geophys. 22, 633 (1966).
  8. S. P. F. Humphreys-Owen, Proc. Roy. Soc. (London) 77, 949 (1961).
    [Crossref]
  9. M. R. Querry, J. Opt. Soc. Am. 59, 876 (1969).
    [Crossref]
  10. Tests show that the normal-incidence reflectance of uncoated aluminum mirrors from commercial sources gradually increases from 0.94 at 2 μm to 0.975 at 15 μ m. Small absorption bands were noted at 8.5 μm for commercially aluminized mirrors.
  11. A. R. Downie, M. C. Magoon, T. Purcell, and B. Crawford, J. Opt. Soc. Am. 43, 941 (1953).
    [Crossref]
  12. In the course of their work, Pontier and Dechambenoy relied on the use of amplifier-gain steps in measuring R and made no corrections for polarizer leakage and spectrograph discrimination. Because the angles of incidence used in the studies of polarized flux were close to Brewster’s angle, the latter two corrections were unnecessary.
  13. P. Queney, Ann. Geophys. 22, 336 (1966).
  14. A. N. Rusk and D. Williams, J. Opt. Soc. Am. 59, 500A (1969).

1969 (2)

M. R. Querry, J. Opt. Soc. Am. 59, 876 (1969).
[Crossref]

A. N. Rusk and D. Williams, J. Opt. Soc. Am. 59, 500A (1969).

1968 (1)

W. M. Irvine and J. B. Pollack, Icarus 8, 324 (1968).
[Crossref]

1966 (1)

P. Queney, Ann. Geophys. 22, 336 (1966).

1965 (1)

L. Pontier and C. Dechambenov, Ann. Geophys. 21, 462 (1965);Ann. Geophys. 22, 633 (1966).

1961 (1)

S. P. F. Humphreys-Owen, Proc. Roy. Soc. (London) 77, 949 (1961).
[Crossref]

1959 (1)

L. D. Kislovskii, Opt. Spectry 7, 201 (1959).

1953 (1)

1941 (1)

1935 (1)

C. H. Cartwright, Nature 135, 872 (1935).
[Crossref]

Cartwright, C. H.

C. H. Cartwright, Nature 135, 872 (1935).
[Crossref]

Centano, M.

Crawford, B.

Dechambenov, C.

L. Pontier and C. Dechambenov, Ann. Geophys. 21, 462 (1965);Ann. Geophys. 22, 633 (1966).

Dorsey, E. N.

E. N. Dorsey, Properties of Ordinary Water Substance (Rheinhold Publ. Co., New York, 1940).

Downie, A. R.

Humphreys-Owen, S. P. F.

S. P. F. Humphreys-Owen, Proc. Roy. Soc. (London) 77, 949 (1961).
[Crossref]

Irvine, W. M.

W. M. Irvine and J. B. Pollack, Icarus 8, 324 (1968).
[Crossref]

Kislovskii, L. D.

L. D. Kislovskii, Opt. Spectry 7, 201 (1959).

Magoon, M. C.

McAlister, E. D.

E. D. McAlister (private communication) indicates that his reflection spectra were obtained with a nonparallel unpolarized beam and that no measurements of spectrograph discrimination were made.

Pollack, J. B.

W. M. Irvine and J. B. Pollack, Icarus 8, 324 (1968).
[Crossref]

Pontier, L.

L. Pontier and C. Dechambenov, Ann. Geophys. 21, 462 (1965);Ann. Geophys. 22, 633 (1966).

Purcell, T.

Queney, P.

P. Queney, Ann. Geophys. 22, 336 (1966).

Querry, M. R.

Rusk, A. N.

A. N. Rusk and D. Williams, J. Opt. Soc. Am. 59, 500A (1969).

Williams, D.

A. N. Rusk and D. Williams, J. Opt. Soc. Am. 59, 500A (1969).

Ann. Geophys. (2)

L. Pontier and C. Dechambenov, Ann. Geophys. 21, 462 (1965);Ann. Geophys. 22, 633 (1966).

P. Queney, Ann. Geophys. 22, 336 (1966).

Icarus (1)

W. M. Irvine and J. B. Pollack, Icarus 8, 324 (1968).
[Crossref]

J. Opt. Soc. Am. (4)

Nature (1)

C. H. Cartwright, Nature 135, 872 (1935).
[Crossref]

Opt. Spectry (1)

L. D. Kislovskii, Opt. Spectry 7, 201 (1959).

Proc. Roy. Soc. (London) (1)

S. P. F. Humphreys-Owen, Proc. Roy. Soc. (London) 77, 949 (1961).
[Crossref]

Other (4)

Tests show that the normal-incidence reflectance of uncoated aluminum mirrors from commercial sources gradually increases from 0.94 at 2 μm to 0.975 at 15 μ m. Small absorption bands were noted at 8.5 μm for commercially aluminized mirrors.

E. D. McAlister (private communication) indicates that his reflection spectra were obtained with a nonparallel unpolarized beam and that no measurements of spectrograph discrimination were made.

E. N. Dorsey, Properties of Ordinary Water Substance (Rheinhold Publ. Co., New York, 1940).

In the course of their work, Pontier and Dechambenoy relied on the use of amplifier-gain steps in measuring R and made no corrections for polarizer leakage and spectrograph discrimination. Because the angles of incidence used in the studies of polarized flux were close to Brewster’s angle, the latter two corrections were unnecessary.

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Figures (8)

F. 1
F. 1

Reflectometer diagram. The components are: Globar A, 13-Hz radiation chopper B, Cassegrain collimator C, polarizer D, sample F, Cassegrain condenser H, monochromator entrances lit J; E and H are plane mirrors. In a later modification, the polarizer was shifted to a position between the sample and the condenser in order to permit more precise determination of incidence angles at the sample.

F. 2
F. 2

Optical arrangement for elimination of the standard reference mirror. Plane mirrors B and C are mechanically coupled and can be shifted to positions B′ and C′ to provide identical optical paths except for reflection at the sample surface.

F. 3
F. 3

Spectral reflectance of water at incidence angles θ = 69.83°±0.23° in the 5000–800-cm−1 region and θ = 71.06° ±0.23° in the 770–400-cm−1 region.

F. 4
F. 4

Spectral reflectance of water at incidence angle θ = 75.43°±0.23°.

F. 5
F. 5

The real part nr of the refractive index as determined by Irvine and Pollack (Δ), Pontier and Dechambenoy(□), and the present study (○).

F. 6
F. 6

Spectral reflectance for various incidence angles as computed from the optical constants in Table I. Rh is the reflectance for flux polarized in the plane of incidence.

F. 7
F. 7

Same as Fig. 6, for Rr, the reflectance for flux polarized normal to the plane of incidence.

F. 8
F. 8

Same as Figs. 6 and 7 but for unpolarized flux.

Tables (1)

Tables Icon

Table I Refractive index of water.