Abstract

A moderate resolution vacuum far ir spectrometer has been built with a data acquisition system designed for computer processing of the data. The spectral range of the instrument is 20–1600 μ. Sensitive low temperature bolometer detectors have been made of doubly doped silicon. The radiation filtering scheme is discussed in detail. In addition, an analysis is made of the effect of detector noise and impurity radiation on the accuracy of the results. Sample spectra illustrating the performance of the instrument are presented.

© 1970 Optical Society of America

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References

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  1. See the review article by F. Kneubühl, Appl. Opt. 8, 505 (1969) and the references therein.
    [CrossRef]
  2. A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
    [CrossRef]
  3. Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
    [CrossRef]
  4. E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
    [CrossRef]
  5. D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
    [CrossRef]
  6. Private communication with W. V. Johnston, Rocketdyne, North American Rockwell Corporation, Canoga Park, California, who first used this material for low temperature thermometers.
  7. I. F. Silvera, to be published.
  8. G. Birnbaum, A. Rosenberg, Phys. Lett. 27A, 272 (1968); A. Rosenberg, G. Birnbaum, J. Chem. Phys. 48, 1396 (1968); W. N. Hardy, I. F. Silvera, K. N. Klump, O. Schnepp, Phys. Rev. Lett. 21, 291 (1968); I. O. Ozier, W. Ho, G. Birnbaum, J. Chem. Phys., to be published; A. Rosenberg, G. Birnbaum, J. Chem. Phys., to be published.
    [CrossRef]

1969 (1)

1968 (2)

D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
[CrossRef]

G. Birnbaum, A. Rosenberg, Phys. Lett. 27A, 272 (1968); A. Rosenberg, G. Birnbaum, J. Chem. Phys. 48, 1396 (1968); W. N. Hardy, I. F. Silvera, K. N. Klump, O. Schnepp, Phys. Rev. Lett. 21, 291 (1968); I. O. Ozier, W. Ho, G. Birnbaum, J. Chem. Phys., to be published; A. Rosenberg, G. Birnbaum, J. Chem. Phys., to be published.
[CrossRef]

1963 (1)

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

1962 (2)

Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
[CrossRef]

E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
[CrossRef]

Birnbaum, G.

G. Birnbaum, A. Rosenberg, Phys. Lett. 27A, 272 (1968); A. Rosenberg, G. Birnbaum, J. Chem. Phys. 48, 1396 (1968); W. N. Hardy, I. F. Silvera, K. N. Klump, O. Schnepp, Phys. Rev. Lett. 21, 291 (1968); I. O. Ozier, W. Ho, G. Birnbaum, J. Chem. Phys., to be published; A. Rosenberg, G. Birnbaum, J. Chem. Phys., to be published.
[CrossRef]

Fujita, S.

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

Gebbie, H. A.

E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
[CrossRef]

Johnston, W. V.

Private communication with W. V. Johnston, Rocketdyne, North American Rockwell Corporation, Canoga Park, California, who first used this material for low temperature thermometers.

Kneubühl, F.

Loewenstein, E. V.

D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
[CrossRef]

Misuishi, A.

Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
[CrossRef]

Mitsuishi, A.

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

Morgan, R. L.

D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
[CrossRef]

Otsuka, Y.

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

Plyler, E. K.

E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
[CrossRef]

Rosenberg, A.

G. Birnbaum, A. Rosenberg, Phys. Lett. 27A, 272 (1968); A. Rosenberg, G. Birnbaum, J. Chem. Phys. 48, 1396 (1968); W. N. Hardy, I. F. Silvera, K. N. Klump, O. Schnepp, Phys. Rev. Lett. 21, 291 (1968); I. O. Ozier, W. Ho, G. Birnbaum, J. Chem. Phys., to be published; A. Rosenberg, G. Birnbaum, J. Chem. Phys., to be published.
[CrossRef]

Silvera, I. F.

I. F. Silvera, to be published.

Smith, D. R.

D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
[CrossRef]

Yamada, Y.

Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
[CrossRef]

Yates, D. J. C.

E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
[CrossRef]

Yoshinaga, H.

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
[CrossRef]

Appl. Opt. (1)

J. Opt. Soc. Amer. (3)

Y. Yamada, A. Misuishi, H. Yoshinaga, J. Opt. Soc. Amer. 52, 17 (1962).
[CrossRef]

E. K. Plyler, D. J. C. Yates, H. A. Gebbie, J. Opt. Soc. Amer. 52, 859 (1962).
[CrossRef]

D. R. Smith, R. L. Morgan, E. V. Loewenstein, J. Opt. Soc. Amer. 58, 433 (1968).
[CrossRef]

Japan. J. Appl. Phys. (1)

A. Mitsuishi, Y. Otsuka, S. Fujita, H. Yoshinaga, Japan. J. Appl. Phys. 2, 574 (1963).
[CrossRef]

Phys. Lett. (1)

G. Birnbaum, A. Rosenberg, Phys. Lett. 27A, 272 (1968); A. Rosenberg, G. Birnbaum, J. Chem. Phys. 48, 1396 (1968); W. N. Hardy, I. F. Silvera, K. N. Klump, O. Schnepp, Phys. Rev. Lett. 21, 291 (1968); I. O. Ozier, W. Ho, G. Birnbaum, J. Chem. Phys., to be published; A. Rosenberg, G. Birnbaum, J. Chem. Phys., to be published.
[CrossRef]

Other (2)

Private communication with W. V. Johnston, Rocketdyne, North American Rockwell Corporation, Canoga Park, California, who first used this material for low temperature thermometers.

I. F. Silvera, to be published.

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Figures (11)

Fig. 1
Fig. 1

The far ir spectrometer installation: (a) electronics, (b) source and filtering section, (c) monochromator section, (d) light pipe gas cell, (e) detector cryostat, (f) liquid helium pump line, (g) cold trap, and (h) hoist.

Fig. 2
Fig. 2

Optical train of the spectrometer. The radiation emanates from the mercury arc lamp and is reflected from two reflection filters. The beam is chopped at a focal plane in the first section. The second section contains the Czerny-Turner grating mount with a transmission filter following the entrance slit and a reflection filter preceding the exit slit. The output is fed out through 1.25-cm brass light pipe with a 2.50-cm entrance cone.

Fig. 3
Fig. 3

Over-all system block diagram.

Fig. 4
Fig. 4

A plot of the fractional error in α, normalized to the noise-to-signal ratio N0, as a function of transmittance. The source of the noise is the detector.

Fig. 5
Fig. 5

The fractional error in absorption coefficient α due to the presence of impurity radiation as a function of transmittance. αm is the measured value, i0 is the impurity-to-signal ratio, and s is the self-filtering parameter described in the text.

Fig. 6
Fig. 6

Characteristics of short wavelength cutoff transmission or reflection filters: (a) an ideal step filter, (b) a typical real filter, and (c) a step filter with losses.

Fig. 7
Fig. 7

Absorption coefficient as a function of frequency for collision induced absorption in gaseous CO2. The arrows along the abscissa indicate changes of filtering.

Fig. 8
Fig. 8

Relative efficiencies of two 6.4-lines/mm gratings. (a) Original grating and (b) replacement grating. All other experimental conditions and scales are identical for both (a) and (b). These curves also illustrate the usual form of the recorder traces which is the output voltage of the integrator. The peak values are recorded on punched tape.

Fig. 9
Fig. 9

The spectral slit function of the spectrometer with triangular, gaussian, and lorentzian line shapes for comparison. The slit width is 3 mm.

Fig. 10
Fig. 10

(a) Water vapor spectrum in the 45–70 cm−1 spectral range. The instrumental resolution is indicated. The integration time was 10 sec/point. (b) A higher resolution spectra of the water vapor doublet at 55.5 cm−1. Integration time was 40 sec/point.

Fig. 11
Fig. 11

The spectrum of solid ortho-hydrogen showing several different computer presentations. (a) Temperature greater than the orientational ordering temperature Tc. Intensity is normalized to the empty cell background spectrum. (b) T < Tc; structure due to optical phonons is now present but the two higher frequency lines are barely discernible. (c) By normalizing the T < Tc spectrum with the T > Tc spectrum, the weak structure is enhanced.

Tables (2)

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Table I Spectrometer Filter Specifications

Tables Icon

Table II Filter Compositions

Equations (7)

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L δ α ¯ = [ ( n / I ) 2 + ( n 0 / I 0 ) 2 ] 1 2 .
δ α ¯ / α = N 0 ( 1 + T 2 ) 1 2 / T ( ln T ) ,
L α m = ln [ ( I 0 + F 0 ) / ( I + F ) ] ,
( α m α ) / α = I n [ ( 1 + i 0 ) / ( 1 + i 0 s / T ) ] ln T ,
r = A T a + b T ( e Q / T ) ,
α = ( 1 / L ) ln [ I ( T ) / I ( empty cell ) ] .
α Δ = ( 1 / L ) ln [ ( I ( 1.33 K ) / I ( 5.36 K ) ]

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