Abstract

The 5 m Jarrell-Ash Czerny-Turner spectrograph at the Institute for Molecular Physics has been adapted to spectrometric operation in the 1–2 μm wavelength region. A lead screw assembly with a stepping motor drive has been installed to translate an exit slit that is focused onto a cooled intrinsic germanium detector. The exceptional sensitivity of this detection system has produced good signal-to-noise ratios in the third order of a 300 line/mm echelle grating which yields a reciprocal dispersion of 1.44 Å/mm at the exit slit. The resolution achieved was energy limited at 0.046 cm−1 and the precision of frequency measurement was 0.007 cm−1. The 0-0 band of the BΣ3u-BΠ3g system of molecular nitrogen was the subject of the investigation. Although this system is known as the infrared afterglow system, the band emits strongly in a dc glow discharge and it has been possible to resolve nearly 1000 lines in the band. The preponderance of the lines in the region are from the 0-0 B′ → B transition, with only a small 1 PG emission toward the red end of the band.

© 1978 Optical Society of America

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References

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  1. W. M. Benesch and K. A. Saum, “The W3Δu state of molecular nitrogen,” J. Phys. B 4, 732–738 (1971).
    [Crossref]
  2. R. Covey, K. A. Saum, and W. Benesch, “Transition probabilities for the W3Δu–B3Πg system of molecular nitrogen,” J. Opt. Soc. Am. 63, 592–596 (1973).
    [Crossref]
  3. K. A. Saum and W. M. Benesch, “Infrared electronic emission spectrum of nitrogen,” Appl. Opt. 9, 195–200 (1970).
    [Crossref] [PubMed]
  4. E. J. Beiting and P. D. Feldman, “Fabrication and performance of intrinsic germanium photodiodes,” Appl. Opt. 16, 800–802 (1977).
  5. D. P. Mathur, R. J. McIntyre, and P. P. Webb, “A new germanium photodiode with extended long-wavelength response,” Appl. Opt. 9, 1842–1847 (1970).
    [Crossref] [PubMed]
  6. William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
    [Crossref]
  7. William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
    [Crossref]

1977 (1)

1973 (1)

1971 (1)

W. M. Benesch and K. A. Saum, “The W3Δu state of molecular nitrogen,” J. Phys. B 4, 732–738 (1971).
[Crossref]

1970 (2)

1966 (2)

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

Beiting, E. J.

Benesch, W.

Benesch, W. M.

W. M. Benesch and K. A. Saum, “The W3Δu state of molecular nitrogen,” J. Phys. B 4, 732–738 (1971).
[Crossref]

K. A. Saum and W. M. Benesch, “Infrared electronic emission spectrum of nitrogen,” Appl. Opt. 9, 195–200 (1970).
[Crossref] [PubMed]

Benesch, William

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

Covey, R.

Feldman, P. D.

Mathur, D. P.

McIntyre, R. J.

Saum, K. A.

Tilford, S. G.

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

Vanderslice, Joseph T.

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

Webb, P. P.

Wilkinson, P. G.

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

Appl. Opt. (3)

Astrophys. J. (2)

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for permitted transitions in N2,” Astrophys. J. 144, 408–418 (1966).
[Crossref]

William Benesch, Joseph T. Vanderslice, S. G. Tilford, and P. G. Wilkinson, “Franck-Condon factors for observed transitions in N2 above 6 eV,” Astrophys. J. 143, 236–252 (1966).
[Crossref]

J. Opt. Soc. Am. (1)

J. Phys. B (1)

W. M. Benesch and K. A. Saum, “The W3Δu state of molecular nitrogen,” J. Phys. B 4, 732–738 (1971).
[Crossref]

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Figures (5)

FIG. 1
FIG. 1

Top view of the scanning mechanism which translates the exit slit across the focal plane of the spectrograph. The free length of the lead screw is 20 in., which leaves 18 in. of scanning length accessible to the nut. The focal plane is uncurved. In the present investigation, the detector is a liquid nitrogen-cooled intrinsic germanium diode. Further details in text.

FIG. 2
FIG. 2

Germanium photodiode mounted in LN2 cryostat. The crystal is positioned between a stainless steel pressure clamp and the copper cold finger. More than 80% of the 1 cm × ~0.5 cm front surface is sensitive to radiation. A gold-sputtered mirror is located behind the crystal to increase the long wavelength quantum efficiency.

FIG. 3
FIG. 3

Preamplifier schematic. All capacitors are in μF unless otherwise specified and all resistors are in ohms. All marked electrolytic capacitors must be rated to withstand the bias voltage.

FIG. 4
FIG. 4

Block diagram of the signal conditioning and recording system. Pathways for data begin at the detector which receives the chopped light and converts it to an electrical signal. Destination points are the chart recorder and the tape recorder, Timing pulses, which are used to control the entire operation including the wavelength drive, are generated in the digital data formatter.

FIG. 5
FIG. 5

The B Σ 3 u - B Π 3 g (0—0) band at low and high resolution. All 4-figure numbers are in wavenumber. The upper trace shows the band, underlined, at 1.53 μm (6545 cm−1). 1PG band origins are marked from above. The middle trace is a high resolution spectrum of the 150 cm−1 interval encompassing most of the underlined band. The bottom trace is a blowup of a 2 cm−1 sample taken from the spot designated.

Equations (3)

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λ f = c ,
Δ λ = - λ 2 Δ f / c .
I ( 1 - 0 ) I ( 0 - 0 ) = q ( 1 - 0 ) q ( 0 - 0 ) ( σ ( 1 - 0 ) σ ( 0 - 0 ) ) 4 .