ityaksov_2008 ============= D\. Ityaksov, H\. Linnartz and W\. Ubachs, Mol\. Phys\. 106, 2471 \(2008\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1080/00268970802570334 `__ **Source kind:** measurement **Recorded technique:** Cavity ring\-down extinction with pressure ramps up to atmospheric pressure \(Eq\. 4\: the slope of the decay rate against density\), frequency\-doubled \(270\.15, 251\.72, 215\.38, 210\.12 nm\) or \-tripled \(203\.76, 199\.27, 198\.48, 197\.70 nm\) pulsed dye lasers, bandwidth below 0\.2 cm^\-1, wavelengths calibrated to about 0\.01 nm; 40 cm and 82 cm cells; Baratron pressure \(0\.15 %\); typically ten ramps per point; 293 \+\- 3 K \(pp\. 3\-4\)\. Purities N2 99\.999 %, CH4 99\.995 %, SF6 99\.8 %\. **Materials in structured entries:** CH4, N2, SF6 **Dataset quantities:** rayleigh\_cross\_section **Contents:** 6 datasets; 7 formulas. Curation notes -------------- The measured quantity is the extinction cross section per molecule, identified with the Rayleigh cross section \(no absorption found for any of the three gases down to 197\.7 nm; an earlier CH4 sample of purity below 99\.5 % showed an absorption onset near 210 nm from impurities, p\. 8\)\. Table 1 gives the measured values with one\-sigma uncertainties \('with 1 sigma uncertainties', p\. 4\) and the values predicted by Eq\. \(2\), sigma = 24 pi^3 / \(lambda^4 N^2\) \(\(n^2 \- 1\)/\(n^2 \+ 2\)\)^2 F\_k, from the formulas below \(check datasets\)\. Wavelengths are not said to be vacuum or air; below 200 nm they can only be vacuum, and all are taken as vacuum \(the difference at 270 nm, 0\.08 nm, moves sigma by 0\.1 %\)\. King factors\: N2 from Bates \(Eq\. 9, varying with wavelength, so no king\_factor parameter is attached to the N2 datasets\); CH4 and SF6 set to 1 \(p\. 6\-7\)\. Check of the predictions \(2026\-09\-25\)\: with Eqs\. \(10\) and \(11\) and N = 2\.5469e19 cm^\-3 \(the ideal gas at 288\.15 K and 101 325 Pa, the reference of those formulas, from sneep\_2005\) the CH4 and SF6 predicted columns are reproduced to 0\.01 printed units at all eight wavelengths; with the laboratory density at 293 K they come out 3\.4 % high\. The N2 column is reproduced by Eqs\. \(8\) and \(9\) with the same 288\.15 K density to 0\.5 % \(the rounding of Eq\. 8's four coefficients\), not with the 293 K density \(3\.6 % high\), although Eq\. \(8\) is said to be scaled to 293 K \(see n2\_eq8\)\. Since the cross section is a per\-molecule quantity, the predictions stand independently of the laboratory temperature\. Table 2 gives power\-law fits sigma = sigma\_0 nu^\(4 \+ epsilon\) \(Eq\. 5, nu in cm^\-1\) to the measured points \('Experimental'\) and to the predictions \('Predicted'\), recorded as formulas\. The text \(p\. 6\) prints N2's epsilon as 0\.543, Table 2 and the Figure 1 caption 0\.534 \(page image checked\)\: the text transposes the digits\. Figures 2, 4 and 6 show refractive indices, polarizabilities, King factors and depolarization ratios derived from the fits; they are not tabulated and not extracted\. **Recorded bibliographic identity status:** VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- ityaksov\_2008/rayleigh\_N2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "rayleigh_N2", "material": "N2", "file": "N2/ityaksov_2008__rayleigh_N2.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" } } Table 1, measured extinction cross section \(seven wavelengths; 210\.12 nm not measured\)\. The total cross section of the anisotropic molecule; the paper's comparison uses Bates's F\_k \(Eq\. 9\)\. The 270\.15 nm value lies outside the prediction's uncertainty, 'due to the relatively low experimental sensitivity at this wavelength' \(p\. 6\)\. ityaksov\_2008/rayleigh\_CH4 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "rayleigh_CH4", "material": "CH4", "file": "CH4/ityaksov_2008__rayleigh_CH4.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "king_factor": 1.0 } } Table 1, measured \(six wavelengths; 203\.76 and 210\.12 nm not measured\)\. F\_k = 1 assumed \(CCl4's small depolarization, p\. 6\)\. ityaksov\_2008/rayleigh\_SF6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "rayleigh_SF6", "material": "SF6", "file": "SF6/ityaksov_2008__rayleigh_SF6.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "king_factor": 1.0 } } Table 1, measured \(seven wavelengths; 203\.76 nm not measured\)\. F\_k = 1 \(p\. 7\)\. ityaksov\_2008/predicted\_N2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "predicted_N2", "material": "N2", "file": "N2/ityaksov_2008__predicted_N2.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "check", "uncertainty": { "column": true, "level": "1 sigma" } } Table 1, predicted from Eqs\. \(8\) and \(9\) \(Griesmann and Burnett's refractive indices, Bates's King factor\); \+\- from those formulas' uncertainties\. Not a measurement\. ityaksov\_2008/predicted\_CH4 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "predicted_CH4", "material": "CH4", "file": "CH4/ityaksov_2008__predicted_CH4.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "check", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "king_factor": 1.0 } } Table 1, predicted from Eq\. \(10\) \(sneep\_2005's fit to Hohm 1993\) with F\_k = 1, extrapolated far below its 325 nm limit\. Not a measurement\. ityaksov\_2008/predicted\_SF6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "predicted_SF6", "material": "SF6", "file": "SF6/ityaksov_2008__predicted_SF6.csv", "table": "tbl_0ec99fd2f68e", "quantity": "rayleigh_cross_section", "unit": "cm2", "scale": 1e-25, "abscissa_unit": "nm", "wavelength_medium": "vacuum", "use": "check", "parameters": { "king_factor": 1.0 } } Table 1, predicted from Eq\. \(11\) \(sneep\_2005's two\-point fit to vukovic\_1996\) with F\_k = 1; no uncertainty printed\. Not a measurement\. Formulas -------- ityaksov\_2008/n2\_eq8 ~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "n2_eq8", "material": "N2", "equation": "Eq. (8), p. 5", "printed": "n(lambda) - 1 = (3.635 lambda^2 / (43.878 x 10^-5 lambda^2 - 1) + 0.0261 lambda^2 / (0.134 x 10^-5 lambda^2 - 1)) x 10^-8", "variable": "lambda: wavelength in Angstrom (the unit is not stated; only Angstrom gives n - 1 near 3e-4), vacuum", "state": { "pressure_pa": 101325.0, "temperature_k": 293.0 }, "density": "real", "range": "about 145-270 nm (Griesmann and Burnett's 31 values)", "coefficients": { "a1": "3.635", "b1": "43.878e-5", "a2": "0.0261", "b2": "0.134e-5" }, "reproduced_from": [ "griesmann_1999" ], "check": "The authors' two-term Sellmeier fit to Griesmann and Burnett's 273.15 K values after scaling them to 293 K and 101 325 Pa with Eqs. (6) and (7) (real gas, Z = 1 - (P/101325)(317.6 - T) x 10^-5). As printed (lambda in A) it gives 0.944-0.946 times griesmann_1999's 273.15 K values at every one of its N2 wavelengths (149-279 nm), whereas the stated scaling to 293 K gives 0.932 (and to 288.15 K, ideal, 0.948): the formula does not correspond to the stated 293 K. With Eq. (9) and N = 2.5469e19 cm^-3 it reproduces Table 1's predicted N2 column to 0.5 % (0.3-0.5 % high, the rounding of 0.0261 alone is 0.2 % of the dominant term). Checked 2026-09-25." } The authors say 'the absolute uncertainty achieved during the fit is better than 0\.1%' \(p\. 5\)\. Not independent of griesmann\_1999 \(curated\)\. ityaksov\_2008/n2\_king\_eq9 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "n2_king_eq9", "material": "N2", "equation": "Eq. (9), p. 5", "printed": "F_k(lambda) = 1.03 + 3.17 x 10^-12 / lambda^2", "variable": "lambda: wavelength in cm", "range": "200-633 nm, 'with an uncertainty better than 1%'", "coefficients": { "a": "1.03", "b": "3.17e-12" }, "reproduced_from": [ "D. R. Bates, Planet. Space Sci. 32, 785 (1984)" ], "check": "Bates's King factor as quoted by sneep_2005 (Eq. 12) has the constant 1.034; here 1.03 (page image checked). With 1.03 Table 1's predicted N2 values are reproduced to 0.5 % (see n2_eq8); 1.034 would raise them by a further 0.4 %. Checked 2026-09-25." } ityaksov\_2008/ch4\_eq10 ~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ch4_eq10", "material": "CH4", "equation": "Eq. (10), p. 6", "printed": "n(lambda) - 1 = (46662 + 4.02 x 10^-6 / lambda^2) x 10^-8", "variable": "lambda: wavelength in cm", "state": "1atm_15C", "density": "ideal", "range": "325-633 nm (Hohm's data), extrapolated here to 197.7 nm", "coefficients": { "a": "46662", "b": "4.02e-6" }, "reproduced_from": [ "sneep_2005" ], "check": "Identical to sneep_2005's Eq. (18); with N = 2.5469e19 cm^-3 and F_k = 1 it reproduces Table 1's predicted CH4 column to 0.01 at all eight wavelengths. Checked 2026-09-25." } ityaksov\_2008/sf6\_eq11 ~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "sf6_eq11", "material": "SF6", "equation": "Eq. (11), p. 8", "printed": "n(lambda) - 1 = (71517 + 5 x 10^-6 / lambda^2) x 10^-8", "variable": "lambda: wavelength in cm", "state": "1atm_15C", "density": "ideal", "range": "633-1300 nm (two points), extrapolated here to 197.7 nm", "coefficients": { "a": "71517", "b": "5e-6" }, "reproduced_from": [ "sneep_2005" ], "check": "sneep_2005's Eq. (21) with 4.996 rounded to 5; with N = 2.5469e19 cm^-3 and F_k = 1 it reproduces Table 1's predicted SF6 column to 0.01. Checked 2026-09-25." } ityaksov\_2008/n2\_power ~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "n2_power", "material": "N2", "equation": "Eq. (5) with Table 2, p. 5", "printed": "sigma_R = sigma nu^(4 + epsilon); experimental sigma = 1.80 +- 0.06 x 10^-46, epsilon = 0.534 +- 0.003; predicted sigma = 1.796 x 10^-46, epsilon = 0.529", "variable": "nu: vacuum wavenumber in cm^-1; sigma_R in cm^2", "range": "197.70-270.15 nm", "coefficients": { "sigma_exp": "1.80e-46", "epsilon_exp": "0.534", "sigma_predicted": "1.796e-46", "epsilon_predicted": "0.529" }, "check": "The predicted pair gives 3.62, 2.456, 0.88 x 10^-25 cm^2 at 197.70, 215.38, 270.15 nm against Table 1's predicted 3.62, 2.43, 0.89. Checked 2026-09-25." } Fitted one parameter at a time \(strong correlation\)\. The text's epsilon = 0\.543 \(p\. 6\) is a transposition of 0\.534\. ityaksov\_2008/ch4\_power ~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ch4_power", "material": "CH4", "equation": "Eq. (5) with Table 2, p. 5", "printed": "experimental sigma = 0.94 +- 0.02 x 10^-46, epsilon = 0.699 +- 0.002; predicted sigma = 0.942 x 10^-46, epsilon = 0.689", "variable": "nu: vacuum wavenumber in cm^-1; sigma_R in cm^2", "range": "197.70-270.15 nm", "coefficients": { "sigma_exp": "0.94e-46", "epsilon_exp": "0.699", "sigma_predicted": "0.942e-46", "epsilon_predicted": "0.689" }, "check": "The predicted pair gives 10.74, 7.19, 2.49 x 10^-25 cm^2 at 197.70, 215.38, 270.15 nm against Table 1's predicted 10.82, 7.25, 2.61 (5 % at 270 nm). Checked 2026-09-25." } ityaksov\_2008/sf6\_power ~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "sf6_power", "material": "SF6", "equation": "Eq. (5) with Table 2, p. 5", "printed": "experimental sigma = 17.90 +- 0.76 x 10^-46, epsilon = 0.490 +- 0.004; predicted sigma = 17.897 x 10^-46, epsilon = 0.490", "variable": "nu: vacuum wavenumber in cm^-1; sigma_R in cm^2", "range": "197.70-270.15 nm", "coefficients": { "sigma_exp": "17.90e-46", "epsilon_exp": "0.490", "sigma_predicted": "17.897e-46", "epsilon_predicted": "0.490" }, "check": "The predicted pair gives 23.64, 16.10, 5.82 x 10^-25 cm^2 at 197.70, 215.38, 270.15 nm against Table 1's predicted 23.71, 16.04, 5.88. Checked 2026-09-25." } 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.