ityaksov_2008#

D. Ityaksov, H. Linnartz and W. Ubachs, Mol. Phys. 106, 2471 (2008)

Source record · Catalogue · Review register

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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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#

{
  "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 review register for the checks and decisions.