Abstract

The effective position of a strong line partially blended with a weaker one is found as a function of their separation for three different line profiles and two line-position criteria. Some practical examples illustrate the use of the results.

© 1978 Optical Society of America

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  1. J. Hartmann, "Ueber die Ausmessung und Reduction der photographischen Aufnahmen von Sternspektren," Astron. Machr. 155, 81–118 (1901).
  2. We may regard noise in the spectrum as equivalent to many random weak blending lines; hence, the peak is less affected by noise than the other criteria, if the noise is filtered to the same spectral resolution as the signal.
  3. L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).
  4. L. D. Gray, "Relative intensity calculation for carbon dioxide-III. Relative line intensities of transition from the vibrational ground state for temperatures from 160 ° to 280 °K," J. Quant. Spectrosc. Radiat. Transfer 7, 795–803 (1967).
  5. L. D. Gray, R. A. Schorn, and E. S. Barker, "High dispersion spectroscopic observations of Venus IV. The weak carbon dioxide band at 7883 Å," Appl. Opt. 8, 2087–2093 (1969).
  6. L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).
  7. L. D. G. Young, "High resolution spectra of Venus—A Review," Icarus 17, 632–658 (1972).
  8. But note that a reduction in the HWHM to 0.08 cm-1 would give practically the same result for a Gaussian profile as 0.09 cm-1 gives for a Lorentzian.
  9. R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).
  10. C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).
  11. "The half-width of the slit image" corresponds to 14.8 µm on the plate, but the full projected width of the slit is given9 as 15 µm. This must be degraded considerably by the photographic linespread function. A HWHM near 15 µm is typical of fast spectroscopic plates in the blue (unsensitized) region.
  12. C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).
  13. P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).
  14. An exact solution for two-component blends of unequal widths was published by J. B. Tatum15 ten years ago, but it is so unwieldy that it has never been used in practical cases.
  15. J. B. ratum, "The blending effect in the measurement of spectroscopic binary spectra," Mon. Not. R. Astron. Soc. 141, 43–55 (1968).

1977

P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).

1972

L. D. G. Young, "High resolution spectra of Venus—A Review," Icarus 17, 632–658 (1972).

1971

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

1970

L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).

1969

1968

J. B. ratum, "The blending effect in the measurement of spectroscopic binary spectra," Mon. Not. R. Astron. Soc. 141, 43–55 (1968).

1967

L. D. Gray, "Relative intensity calculation for carbon dioxide-III. Relative line intensities of transition from the vibrational ground state for temperatures from 160 ° to 280 °K," J. Quant. Spectrosc. Radiat. Transfer 7, 795–803 (1967).

1966

C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).

1958

R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).

1901

J. Hartmann, "Ueber die Ausmessung und Reduction der photographischen Aufnahmen von Sternspektren," Astron. Machr. 155, 81–118 (1901).

Adams, E. F.

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

Andrews, D. H.

R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).

Babcock, H. D.

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

Barker, E. S.

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

L. D. Gray, R. A. Schorn, and E. S. Barker, "High dispersion spectroscopic observations of Venus IV. The weak carbon dioxide band at 7883 Å," Appl. Opt. 8, 2087–2093 (1969).

Conti, P. S.

P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).

Gray, L. D.

L. D. Gray, R. A. Schorn, and E. S. Barker, "High dispersion spectroscopic observations of Venus IV. The weak carbon dioxide band at 7883 Å," Appl. Opt. 8, 2087–2093 (1969).

L. D. Gray, "Relative intensity calculation for carbon dioxide-III. Relative line intensities of transition from the vibrational ground state for temperatures from 160 ° to 280 °K," J. Quant. Spectrosc. Radiat. Transfer 7, 795–803 (1967).

Hartmann, J.

J. Hartmann, "Ueber die Ausmessung und Reduction der photographischen Aufnahmen von Sternspektren," Astron. Machr. 155, 81–118 (1901).

Houtgast, J.

C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).

John, C. E. St.

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

Leep, E. M.

P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).

Lorre, J. J.

P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).

McDonald, J. K.

R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).

Minnaert, M. G. J.

C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).

Moore, C. E.

C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

Petrie, R. M.

R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).

ratum, J. B.

J. B. ratum, "The blending effect in the measurement of spectroscopic binary spectra," Mon. Not. R. Astron. Soc. 141, 43–55 (1968).

Schorn, R. A.

L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).

L. D. Gray, R. A. Schorn, and E. S. Barker, "High dispersion spectroscopic observations of Venus IV. The weak carbon dioxide band at 7883 Å," Appl. Opt. 8, 2087–2093 (1969).

Schorn, R. A. J.

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

Tatum, J. B.

An exact solution for two-component blends of unequal widths was published by J. B. Tatum15 ten years ago, but it is so unwieldy that it has never been used in practical cases.

Ware, L. M.

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

Woszczyk, A.

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

Young, A. T.

L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).

Young, L. D. G.

L. D. G. Young, "High resolution spectra of Venus—A Review," Icarus 17, 632–658 (1972).

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

Young, L. D. Gray

L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).

Acta Astron.

L. D. G. Young, R. A. J. Schorn, E. S. Barker, and A. Woszczyk, "High dispersion spectroscopic observations of Venus during 1968 and 1969. I. The carbon dioxide bands at 7820 Å and 7883 Å," Acta Astron. 21, 329–363 (1971).

Appl. Opt.

Astron. Machr.

J. Hartmann, "Ueber die Ausmessung und Reduction der photographischen Aufnahmen von Sternspektren," Astron. Machr. 155, 81–118 (1901).

Astrophys. J.

P. S. Conti, E. M. Leep, and J. J. Lorre, "Spectroscopic studies of O-type stars. VIII. Radial velocities and the K-term," Astrophys. J. 214, 759–772 (1977).

Icarus

L. D. G. Young, "High resolution spectra of Venus—A Review," Icarus 17, 632–658 (1972).

J. Quant. Spectrosc. Radiat. Transfer

L. D. Gray Young, A. T. Young, and R. A. Schorn, "Improved Constants for the 7820 Å and 7883 Å bands of CO2," J. Quant. Spectrosc. Radiat. Transfer 10, 1291–1300 (1970).

L. D. Gray, "Relative intensity calculation for carbon dioxide-III. Relative line intensities of transition from the vibrational ground state for temperatures from 160 ° to 280 °K," J. Quant. Spectrosc. Radiat. Transfer 7, 795–803 (1967).

Mon. Not. R. Astron. Soc.

J. B. ratum, "The blending effect in the measurement of spectroscopic binary spectra," Mon. Not. R. Astron. Soc. 141, 43–55 (1968).

Natl. Bur. Stand. (U.S.) Monog.

C. E. Moore, M. G. J. Minnaert, and J. Houtgast, "The solar spectrum 2935 Å to 8770 Å, Natl. Bur. Stand. (U.S.) Monog. 61 (1966).

Publ. Dom. Astrophys. Obs., Victoria, B. C.

R. M. Petrie, D. H. Andrews, and J. K. McDonald, "Wave-length standards for radial-velocity determinations. Spectral types A3-K8 with low dispersion," Publ. Dom. Astrophys. Obs., Victoria, B. C. 10, 415–423 (1958).

Other

C. E. St. John, C. E. Moore, L. M. Ware, E. F. Adams, and H. D. Babcock, Revision of Rowland's Preliminary Table of Solar Spectrum Wave-Lengths, Carnegie Inst. Wash. Publ. 396; Pap. Mt. Wilson Obs. 3 (1928).

"The half-width of the slit image" corresponds to 14.8 µm on the plate, but the full projected width of the slit is given9 as 15 µm. This must be degraded considerably by the photographic linespread function. A HWHM near 15 µm is typical of fast spectroscopic plates in the blue (unsensitized) region.

But note that a reduction in the HWHM to 0.08 cm-1 would give practically the same result for a Gaussian profile as 0.09 cm-1 gives for a Lorentzian.

An exact solution for two-component blends of unequal widths was published by J. B. Tatum15 ten years ago, but it is so unwieldy that it has never been used in practical cases.

We may regard noise in the spectrum as equivalent to many random weak blending lines; hence, the peak is less affected by noise than the other criteria, if the noise is filtered to the same spectral resolution as the signal.

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