matsumoto_1987#

H. Matsumoto, “The refractivity of CO2 gas in the region of 10 um”, Appl. Phys. B 44, 147 (1987)

Source record · Catalogue · Review register

Source kind: measurement

Recorded technique: Two-beam interferometer with a ZnSe beam splitter and a 2 m vacuum cell with BaF2 windows, run simultaneously with a 0.63 um He-Ne laser and a 10.6 um CO2 laser on the 10.4 um band’s P(20) line; fringes recorded while CO2 is admitted gradually, the phase from the intensity between its extremes (Eq. 4), the CO2 laser’s extremes found by scanning a PZT. The laser’s frequency is swept by +-25 MHz through the gain curve and measured by beating with a second, stabilised CO2 laser (pp. 147-148, Fig. 1). Maximum pressure 600-1300 Pa (‘several hundreds of pascals’, p. 148), the fringe order changing by less than one, its fraction read to better than 1/100 of a fringe (p. 149); room at 18-21 degrees C (p. 148).

Materials in structured entries: CO2

Dataset quantities: refractivity

Contents: 1 dataset; 0 formulas.

Curation notes#

Page numbers are the journal’s (147-149; pdf page 1 = p. 147).

What was measured (p. 148, Table 1): the ratio R = (n - 1)_infrared/(n - 1)_visible of the CO2-laser and He-Ne fringe counts in the same gas at the same time, at the line centre v0 and at v0 -+ 25 MHz: 0.981 (sigma 0.024, N = 14), 0.989 (0.016, 7) and 0.972 (0.011, 5), sigma the standard deviation of the N measurements. The pressure is not measured: ‘Utilizing the Koch’s formula in the visible region, the pressure of the CO2 gas in the cell is determined from the values by the He-Ne laser’ (p. 148), so Table 2’s refractivities at 101325 Pa and 20 degrees C are R times Koch’s visible refractivity there: each is R x 417.0e-6 to the printed digit (409.08, 412.41, 405.32), the visible value implied by all three rows lying in 416.97-417.03 (checked 2026-10-01). The ratio is not extracted: the vocabulary has no quantity for a gas’s refractivity over its own at another wavelength (refractivity_ratio is against another material at the same density).

State and density: ‘at 101325 Pa and 20 °C’ (Table 2’s caption), through Koch’s formula (the paper cites Owens, Appl. Opt. 6, 51 (1967)); how that formula relates the refractivity to the density is not stated here. The real and ideal densities of CO2 at 1 atm and 20 degrees C differ by about 0.5 %, a quarter of the stated accuracy: the density is recorded as unknown (the loader then uses the real-gas density).

Wavelength: the 10.4 um band’s P(20) line (p. 148), called the ‘10.6-um CO2-laser’ in the text (p. 148) and ‘lambda = 10.6 um’ on Fig. 2. No wavelength or wavenumber of the line is printed; 10.6 um is stored, as vacuum. The same line is 944.2 cm^-1 (10.591 um) in marchetti_2007’s table (1P20): the 0.09 % in wavelength changes CO2’s refractivity by 0.03 % (marchetti_2007’s Eq. 4 and fit/CO2 alike), far below the precision. The three rows are 25 MHz apart (1e-6 of the frequency); the paper finds ‘The measured values are not different in the gain curve’ (p. 148), its Eq. (3) putting the line’s own anomalous dispersion at about 1e-7 at 1 atm (0.02 % of n - 1; p. 147).

Uncertainty: ‘the over-all accuracy of the measurement is better than 2%’ (p. 149; ‘an experimental error of 2%’, abstract, p. 147), level not stated; the errors of the pressure and the cell length cancel in the ratio (p. 149). The per-row standard deviations of R (1.1-2.4 % of a single measurement; 0.5-0.6 % as standard errors of the means) are not the refractivity’s uncertainty and are not stored. The three rows spread by 1.7 % (0.972 to 0.989), more than their standard errors.

Doubtful: Table 2’s last column, (n_m - n_c) x 10^6 against Koch’s formula, prints -1.3, 2.1 and 5.0 (image checked). The first two give Koch’s value at 10.6 um as 410.4 and 410.3 (the text’s ‘about 410 x 10^-6’, p. 147); the third gives 400.3, unless the printed 5.0 should be -5.0 (405.3 - 410.3). That column is a calculation and is not extracted, so no erratum is needed; the sign of its last row cannot be settled from the paper.

Consistency (2026-10-01): Koch’s implied 417.0e-6 at 0.63 um is 0.12 % above fit/CO2 at 632.99 nm, 101325 Pa and 20 degrees C with the real-gas density (0.66 % with the ideal; 632.99 nm is the He-Ne line’s vacuum wavelength, quoted from memory: the paper says 0.63 um). The ratio R, free of Koch’s formula and of the density, averages 0.9794 (+-0.0033, the rows weighted by their standard errors; chi-squared 4.8 for 2 degrees of freedom) against fit/CO2’s 0.9909 for 10.6 um over 632.99 nm, -1.2 %. Marchetti and Simili’s 1P20 value (marchetti_2007) is 1.4 % above the rows’ mean, Simmons’s 944 cm^-1 and Willetts and Harris’s 10.59 um values 1.0-1.9 % below it (in the polarizability): all within the 2 %.

Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets#

matsumoto_1987/measured_CO2#

{
  "id": "measured_CO2",
  "material": "CO2",
  "file": "CO2/matsumoto_1987__measured_CO2.csv",
  "table": "tbl_a8b02d951b7a",
  "quantity": "refractivity",
  "scale": 1e-06,
  "abscissa_unit": "um",
  "wavelength_medium": "vacuum",
  "state": {
    "pressure_pa": 101325.0,
    "temperature_c": 20.0
  },
  "density": "unknown",
  "use": "check",
  "uncertainty": {
    "relative": 0.02,
    "level": "not stated"
  }
}

Table 2 (p. 148), column (n - 1)_m x 10^6: CO2 on the 10.4 um band’s P(20) line (10.6 um as printed) at its centre (v0) and 25 MHz either side (v0-dv, v0+dv), each R of Table 1 times Koch’s visible refractivity at 101325 Pa and 20 degrees C (417.0e-6, implied). A check: the three rows are one line, and their 2 % is larger than Marchetti and Simili’s 0.3-0.7 %.

Formulas#

No formulas are recorded.

Corrections#

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.