Abstract

The performance of the Perkin-Elmer Model 21 Recording Infra-Red Spectrophotometer has been tested by measuring known spectra under a wide variety of operating conditions. A complete infra-red spectrum in the rock salt region can be recorded as a graph of percent transmittance vs. wave-length in less than 10 minutes. At slower speeds resolving power can be varied from the normal of 30 percent to 40 percent up to about 60 percent of the Rayleigh limit. For extreme resolution or stability, the r.m.s. noise level of 10−9 volts or 2×10−10 watts at the fastest response speed can be reduced as far as 2×10−10 volts or 4×10−11 watts by increasing the response time. The extreme ranges of the operating conditions are: response time, 4.5 to 110 seconds for full scale; scanning rate, 0.5 to 400 minutes per micron; chart scale length, 1 to 50 inches per micron; slit width, to give constant energy levels between. 01 and 2 r.m.s. microvolts full scale. The effects of scattered light and atmospheric absorption bands are less than 3 percent throughout. Operation is automatic after the conditions are selected and the instrument turned on. These features are illustrated in photographic reproductions of original records with more detailed data on the independent performance of the instrument’s more critical parts.

© 1950 Optical Society of America

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References

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  1. J. U. White and M. D. Liston, J. Opt. Soc. Am. 40, 29 (1950).
    [Crossref]
  2. M. D. Liston and J. U. White, J. Opt. Soc. Am. 40, 36 (1950).
    [Crossref]
  3. For a survey of comparative results on other instruments and general information on infra-red spectroscopy the reader is referred to a review article by V. Z. Williams, Rev. Sci. Inst. 19, 135 (1948).
    [Crossref]
  4. Private communication from Darwin L. Wood.

1950 (2)

1948 (1)

For a survey of comparative results on other instruments and general information on infra-red spectroscopy the reader is referred to a review article by V. Z. Williams, Rev. Sci. Inst. 19, 135 (1948).
[Crossref]

Liston, M. D.

White, J. U.

Williams, V. Z.

For a survey of comparative results on other instruments and general information on infra-red spectroscopy the reader is referred to a review article by V. Z. Williams, Rev. Sci. Inst. 19, 135 (1948).
[Crossref]

Wood, Darwin L.

Private communication from Darwin L. Wood.

J. Opt. Soc. Am. (2)

Rev. Sci. Inst. (1)

For a survey of comparative results on other instruments and general information on infra-red spectroscopy the reader is referred to a review article by V. Z. Williams, Rev. Sci. Inst. 19, 135 (1948).
[Crossref]

Other (1)

Private communication from Darwin L. Wood.

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Figures (16)

Fig. 1
Fig. 1

Benzene spectrum showing I0 and scattered light using grating filter; 0.025-mm cell, 0.2μv full scale, 8 minutes per run.

Fig. 2
Fig. 2

Ammonia spectrum showing scattered light without filter; 0.2μv full scale, 9 1 2 minutes per run.

Fig. 3
Fig. 3

Ethylene spectrum measured at different speeds; 10-cm gas cell, 0.3μv full scale.

Fig. 4
Fig. 4

Resolution of the 10μ ammonia band at different slit widths.

Fig. 5
Fig. 5

Infra-red spectrum of benzylamine on three different wave-length scales.

Fig. 6
Fig. 6

Compensation of solvents; 0.5mμv full scale, 8–9 minutes per spectrum.

Fig. 7
Fig. 7

Compensation of solvents; 0.5μv full scale, 8–9 minutes per run.

Fig. 8
Fig. 8

Fixed wave-length absorption by CO2 in breadth with 10-cm cell.

Fig. 9
Fig. 9

Linearity of wedge aperture.

Fig. 10
Fig. 10

Linearity in measuring 6.8 propane absorption band.

Fig. 11
Fig. 11

Two repeat runs of isooctane spectrum showing I0 and scattered light using grating filter; 0.1-mm cell, 0.4μV full scale, 5 minutes per run.

Fig. 12
Fig. 12

Noise level and speed of response.

Fig. 13
Fig. 13

Effect of change in amplifier gain on noise level and speed of response. The curves are numbered for their response speed settings. The relative gains of the plotted points are: ●, 100 percent; ×, 88 percent; +, 57 percent; △, 37 percent; □, 19 percent; ○, 9 percent.

Fig. 14
Fig. 14

Noise and response to transient impulses at fixed gain and different energy levels. Response 1 is adjusted for minimum noise, response 2 for maximum range of operability. Percent noise is peak-to-peak percentage of full scale. Microvolt noise is r.m.s.

Fig. 15
Fig. 15

Adjustment and performance of wave-length cam.

Fig. 16
Fig. 16

Spectral energy distribution for six different settings of the slit cam.

Tables (1)

Tables Icon

Table I Scanning rate and peak-to-peak noise level for different slit schedules and response times. Noise is expressed as percent of full scale and scanning rate in minutes per micron.