matsumoto_1987 ============== H\. Matsumoto, "The refractivity of CO2 gas in the region of 10 um", Appl\. Phys\. B 44, 147 \(1987\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1007/bf00692315 `__ **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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "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 :doc:`review register ` for the checks and decisions.