au_1993 ======= J\. W\. Au, G\. Cooper, G\. R\. Burton, T\. N\. Olney and C\. E\. Brion, "The valence shell photoabsorption of the linear alkanes, CnH2n\+2 \(n=1\-8\)\: absolute oscillator strengths \(7\-220 eV\)", Chem\. Phys\. 173, 209 \(1993\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1016/0301\-0104\(93\)80142\-v `__ **Source kind:** measurement **Recorded technique:** Dipole \(e,e\) spectroscopy\. Low resolution \(1 eV FWHM, 8 keV, zero mean scattering angle\)\: background\-subtracted energy\-loss spectra at 0\.5, 1\.0 and 2\.0 eV intervals over 7\-40, 40\-80 and 80\-220 eV, Bethe\-Born converted; the valence\-shell fraction above 220 eV from a fit of Eq\. \(1\), df/dE = A E^\-2 \+ B E^\-3 \+ C E^\-4, to 130\-220 eV; the whole TRK\-normalised to the number of valence electrons plus about 5 % for Pauli\-excluded inner\-shell transitions \(8\.33 for CH4\)\. High resolution \(0\.048 eV FWHM, 3 keV\)\: from the first threshold to at least 50 eV, normalised to the low resolution in the smooth continuum above about 20 eV \(figures only\)\. Matheson CH4, 99\.8 % \(pp\. 2\-4\)\. **Materials in structured entries:** CH4 **Dataset quantities:** differential\_oscillator\_strength, ionization\_energy **Contents:** 3 datasets; 1 formula. Curation notes -------------- Values per molecule; no density or state involved \(room\-temperature gas, not stated\)\. Only CH4 is curated\. 'The absolute oscillator strength scales are estimated to have an accuracy of \+\-5%' \(p\. 3\)\. CH4 \(datasets\)\: Table 7 \(p\. 22\), the low\-resolution df/dE at 7\.5\-220 eV \(176 points\); the Eq\. \(1\) tail fit with Table 2's CH4 coefficients \(formula tail\_fit\_CH4\); Table 1's quoted vertical ionisation potentials \(13\.6, 14\.4, 15\.0 eV for the Jahn\-Teller split 1t2^\-1 band, Kimura et al\.'s HeI handbook; 22\.91 eV for 2a1^\-1, Potts and Streets 1974\)\. Sums computed from Table 7 \(2026\-09\-27; trapezoid plus the tail above 220 eV\)\: S\(0\) = 7\.915 over 7\.5\-220 eV and 8\.330 in all \(the normalisation 8\.33\); S\(\-1\) = 10\.533, S\(\-2\) = 17\.063 au, S\(\-3\) = 31\.45, S\(\-4\) = 63\.56, S\(\-5\) = 137\.9, S\(\-6\) = 316\.6\. The paper prints no S\(k\)\. Olney et al\. \(1997, olney\_1997\) refine this spectrum for their CH4 dipole sums\. Comparisons \(pp\. 4\-6\)\: good agreement with Okabe and Becker, Samson et al\. and Backx et al\. \(1975; the last higher above 48 eV, attributed to its background subtraction\); de Reilhac and Damany differ below 45 eV; Koch and Skibowski and Metzger and Cook differ in shape; the present data fall between Koch and Skibowski's and Lee et al\.'s synchrotron data at 21\-24 eV\. The recommended average DOSD values of Jhanwar, Meath and MacDonald \(Can\. J\. Phys\. 59, 185 \(1981\), not in the library\) are compared in the figures only\. Table 3 \(p\. 7\)\: the energies \(experimental and calculated\), term values and proposed Rydberg assignments of eight features of the high\-resolution CH4 spectrum \(1\: 9\.7 eV and 2\: 10\.5 eV, the Jahn\-Teller split 1t2 \-\> 3s; 3\-8 at 11\.8\-14\.1 eV, 1t2 \-\> 4s, 3p, 3d, 4d\), from Eq\. \(2\) with R = 13\.606 eV and quantum defects 1\.13 \(s\), 0\.6 \(p\), 0 \(d\)\: no quantity for a band position or term value; not extracted\. Figs\. 1\-2 \(CH4 low\- and high\-resolution spectra\) are figures only\. THE OTHER ALKANES \(not curated; not extracted\)\: Table 1 also lists the vertical IPs of C2H6, C3H8 and C4H10; Table 2 the Eq\. \(1\) coefficients of C2H6 \.\.\. C8H18 \(5\.4, 5\.3, 4\.4, 4\.4, 4\.4, 4\.4, 5\.1 % above 220 eV\); Tables 4\-6 the feature assignments of C2H6, C3H8, C4H10; Tables 8\-14 the df/dE of C2H6 \(7\.5\-220 eV\), C3H8, C4H10, C5H12, C6H14, C7H16 and C8H18; TRK normalisations 14\.54, 20\.75, 26\.96, 33\.17, 39\.38, 45\.59, 51\.80\. Fig\. 4 caption\: the C2H6 1e\_g \-\> 3s band \(Gaussian fit centred at 8\.7 eV\) holds 2\.15e\-2; the C2H6 band at 8\.7\-10\.1 eV about 0\.26 \(p\. 10\)\. Small peaks at 12\.97 eV in the C2H6 and C4H10 spectra are N2 impurity \(p\. 4\)\. **Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- au\_1993/continuum ~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "continuum", "material": "CH4", "file": "CH4/au_1993__continuum.csv", "table": "tbl_f5a4c303b9e9", "quantity": "differential_oscillator_strength", "unit": "1/eV", "scale": 0.01, "abscissa_unit": "eV", "use": "primary", "uncertainty": { "relative": 0.05, "level": "not stated" } } Table 7 \(unlabelled in the extraction\)\: low\-resolution \(1 eV FWHM\) dipole \(e,e\) absolute df/dE of CH4 \(10^\-2 eV^\-1\), 7\.5\-220 eV, 176 points in print order \(0\.5 eV steps to 40 eV, 1 eV to 80 eV, 2 eV to 220 eV\); TRK\-normalised to 8\.33 with the Eq\. \(1\) tail \(formula tail\_fit\_CH4\)\. Uncertainty \+\-5 % \(p\. 3\)\. au\_1993/vertical\_outer ~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "vertical_outer", "material": "CH4", "file": "CH4/au_1993__vertical_outer.csv", "table": "tbl_8bb88b5f26fe", "quantity": "ionization_energy", "unit": "eV", "abscissa": "label", "use": "reproduced", "reproduced_from": [ "K. Kimura, S. Katsumata, Y. Achiba, T. Yamazaki and S. Iwata, Handbook of HeI Photoelectron Spectra of Fundamental Organic Molecules (Japan Scientific Society, Tokyo, 1981)" ], "parameters": { "kind": "vertical", "final_state": "1t2^-1 (X 2T2), the Jahn-Teller components" } } Table 1, CH4 outer valence\: the vertical ionisation potentials of the 1t2 orbital, three values \(13\.6, 14\.4, 15\.0 eV\) for the Jahn\-Teller split band \(the paper's discussion, p\. 6\), rows 1t2\_1\-1t2\_3, quoted from Kimura et al\.'s handbook \(Ref\. \[32\]\)\. The same three maxima as bieri\_1977's vertical\_CH4 \(Heilbronner et al\.\)\. No uncertainty printed\. au\_1993/vertical\_inner ~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "vertical_inner", "material": "CH4", "file": "CH4/au_1993__vertical_inner.csv", "table": "tbl_8bb88b5f26fe", "quantity": "ionization_energy", "unit": "eV", "abscissa": "label", "use": "reproduced", "reproduced_from": [ "A. W. Potts and D. G. Streets, J. Chem. Soc. Faraday Trans. II 70, 875 (1974)" ], "parameters": { "kind": "vertical", "final_state": "2a1^-1 (2A1)" } } Table 1, CH4 inner valence\: the vertical ionisation potential of the 2a1 orbital, 22\.91 eV \(row 2a1\), quoted from Potts and Streets \(Ref\. \[33\]\)\. bieri\_1977 gives 22\.9 eV\. No uncertainty printed\. Formulas -------- au\_1993/tail\_fit\_CH4 ~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "tail_fit_CH4", "material": "CH4", "equation": "Eq. (1), p. 4, with Table 2 (p. 4), CH4 row", "printed": "df/dE = A E^-2 + B E^-3 + C E^-4; CH4: A (eV) = 1.4128x10^2, B (eV^2) = -2.8212x10^4, C (eV^3) = 2.0379x10^6, 5.0 % area above 220 eV", "variable": "E: photon energy in eV; df/dE in eV^-1", "state": "none (per molecule)", "density": "none", "range": "fitted over 130-220 eV; integrated from 220 eV to infinity for the valence-shell tail", "coefficients": { "A": "1.4128e2", "B": "-2.8212e4", "C": "2.0379e6" }, "check": "The integral from 220 eV to infinity is 0.4145, 4.98 % of 8.33 (Table 2: 5.0 %); the curve gives 0.114e-2 /eV at 220 eV, 0.146e-2 at 180 eV and 0.265e-2 at 130 eV against Table 7's 0.12, 0.15 and 0.26 (computed 2026-09-27)." } The paper's high\-energy extrapolation of the CH4 low\-resolution df/dE \(Fig\. 1a insert\)\. Printed as mantissa x 10^n; stored in e\-notation, digits unchanged\. The other alkanes' coefficients are in the source notes\. 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.