Abstract

An automatic recording spectrophotometer designed to cover the range 10,000 to 2000A is described. With present light sources the instrument will trace absorption curves at high speed from 9800A to 3400A, and can be used somewhat more slowly to cover the spectrum to 2300A. A ten-foot concave grating monochromator with fixed slits is used to provide a spectral band 0.5 to 10A wide, the purity available depending on the light intensity and the speed of recording desired. An 11-stage electron multiplier is used to balance a light beam which has passed through the sample to be measured, against the same beam later reduced by a photometric disk by a recorded amount. An electric “memory” device is used to accomplish this balance, and at the instant of balance a spark is passed through a piece of suitable graph paper wrapped around a rotating cylinder. Twenty absorption measurements can thus be made and recorded per second. The instrument will plot either transmission or density values against wave-lengths on a linear scale, to an accuracy of about 1 percent.

© 1940 Optical Society of America

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References

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  1. G. R. Harrison, Proceedings of the Sixth Conference on Spectroscopy (Wiley, 1939), p. 91. (See also G. R. Harrison, J. Opt. Soc. Am. 28, 49 (1938).)
    [Crossref]
  2. G. R. Harrison, Proceedings of the Fifth Conference on Spectroscopy (Wiley, 1938), p. 31.
  3. V. K. Zworykin, J. Opt. Soc. Am. 29, 84 (1939).
    [Crossref]
  4. R. E. Meagher and E. P. Bentley, Rev. Sci. Inst. 10, 336 (1939).
    [Crossref]
  5. A. C. Hardy, J. Opt. Soc. Am. 25, 305 (1935).
    [Crossref]

1939 (2)

V. K. Zworykin, J. Opt. Soc. Am. 29, 84 (1939).
[Crossref]

R. E. Meagher and E. P. Bentley, Rev. Sci. Inst. 10, 336 (1939).
[Crossref]

1935 (1)

Bentley, E. P.

R. E. Meagher and E. P. Bentley, Rev. Sci. Inst. 10, 336 (1939).
[Crossref]

Hardy, A. C.

Harrison, G. R.

G. R. Harrison, Proceedings of the Sixth Conference on Spectroscopy (Wiley, 1939), p. 91. (See also G. R. Harrison, J. Opt. Soc. Am. 28, 49 (1938).)
[Crossref]

G. R. Harrison, Proceedings of the Fifth Conference on Spectroscopy (Wiley, 1938), p. 31.

Meagher, R. E.

R. E. Meagher and E. P. Bentley, Rev. Sci. Inst. 10, 336 (1939).
[Crossref]

Zworykin, V. K.

J. Opt. Soc. Am. (2)

Rev. Sci. Inst. (1)

R. E. Meagher and E. P. Bentley, Rev. Sci. Inst. 10, 336 (1939).
[Crossref]

Other (2)

G. R. Harrison, Proceedings of the Sixth Conference on Spectroscopy (Wiley, 1939), p. 91. (See also G. R. Harrison, J. Opt. Soc. Am. 28, 49 (1938).)
[Crossref]

G. R. Harrison, Proceedings of the Fifth Conference on Spectroscopy (Wiley, 1938), p. 31.

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Figures (6)

Fig. 1
Fig. 1

Layout of principal parts of the grating monochromator. The tracks of the grating-carriage at G are inclined toward a point midway between the entrance slit X and the exit slit Y. The drawing is not to scale.

Fig. 2
Fig. 2

The two photometric disks in which the length of the entrance slit is varied with angle linearly (a) and logarithmically (b). The section through K shows the movable edges of the openings, which can be adjusted to give accuracy to 1 percent.

Fig. 3
Fig. 3

Response of the amplifier and the memory condenser during a photometric cycle. During the first part of the cycle, when the memory commutator is closed, the light is passed through the sample being measured; thereafter it passes through the blank cell and is reduced by the photometric disk until an intensity match is produced. The dotted curves show how the null method used avoids dependence on a linear response of the circuit.

Fig. 4
Fig. 4

Block diagram of the electrical circuit.

Fig. 5
Fig. 5

Details of the electrical circuit, from the electron multipler which measures the light to the sparking device which records the balance point.

Fig. 6
Fig. 6

Typical transmission curves for transformer oils obtained with the recording spectrophotometer in 80 seconds each.