bieri_1977#
G. Bieri, F. Burger, E. Heilbronner and J. P. Maier, “Valence Ionization Energies of Hydrocarbons”, Helv. Chim. Acta 60, 2213 (1977)
Source record · Catalogue · Review register
Source kind: compilation
Recorded technique: He(I alpha) (21.22 eV) and He(II alpha) (40.80 eV) photoelectron spectroscopy (Turner-type cylindrical analysers, polystyrene-film filtered He(II) source), calibrated on the He+ peaks at 24.58 and 17.02 eV, of 143 hydrocarbons; the tables collect the band maxima from this laboratory and from the literature, each column with its reference (pp. 2214-2218, 2230-2231).
Materials in structured entries: CH4
Dataset quantities: ionization_energy
Contents: 2 datasets; 0 formulas.
Curation notes#
PDF pages 1-21 = journal pages 2213-2233. Identity checked on the first page. CH4 is the only curated species.
WHAT THE TABLES HOLD (legend, p. 2218; also p. 2218 above it): ‘All ionization energies listed (in eV) refer to the position of the corresponding band maximum I_j^m in the photoelectron spectrum of the hydrocarbon with an accuracy of +-0.1 eV. For all practical purposes I_j^m ~ I_j^v = vertical ionization energy. ... adiabatic ionization energies I_j^a are given in italics or in the footnotes, with an estimated accuracy of +-0.02 eV. Numbers in square brackets are the references and a star in square brackets ([*]) indicates that these are new values determined in the course of this work. A given reference number is valid also for all successive values in the column until a new reference number appears.’ The positions of maxima above 23 eV are uncertain by +-0.2 eV or more (p. 2218).
CH4 (first table of Section A, p. 2218, tbl_1342dbc497d6, cells only; image checked): 1t2: 13.6^a, 14.4^a, 15.0^a [17]; 2a1: 22.9^b. The only reference in the CH4 column is [17] = E. Heilbronner, T. B. Jones and J. P. Maier, Helv. Chim. Acta 60, 1697 (1977), so by the legend every CH4 value is reproduced from it; none is marked [*]. Footnotes (printed after the Section A tables, p. 2222, page image checked): ‘a) Band maxima of Jahn-Teller distorted 2T_d-band [sic, the 2T2 band]. The adiabatic ionization potential is I_1^a = 12.75 eV. b) Adiabatic ionization energy I_1^a = 22.39 eV.’ The footnoted adiabatic values are recorded as reproduced from the same reference (the legend’s rule; the footnotes cite nothing else).
BEARING: the NIST WebBook’s vertical CH4 value (13.6 +- 0.1 eV, nist_webbook_2026/ vertical_CH4) cites this paper; it is Heilbronner, Jones & Maier’s first Jahn-Teller maximum. The adiabatic 12.75 eV of footnote a is 0.14 eV above Berkowitz et al.’s photoionisation onset (berkowitz_1987, 12.61 eV); that paper lists Brundle, Robin & Basch’s 12.75 eV among the earlier adiabatic values, which range from 12.55 to 12.78 eV.
NOT EXTRACTED: the other 142 hydrocarbons (C2H6, C2H4, C2H2 ...; out of scope), the orbital assignment table of the C3 hydrocarbons (p. 2217) and the spectra of Figs. 1-8.
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
bieri_1977/vertical_CH4#
{
"id": "vertical_CH4",
"material": "CH4",
"file": "CH4/bieri_1977__vertical_CH4.csv",
"table": "tbl_1342dbc497d6",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "reproduced",
"reproduced_from": [
"heilbronner_1977"
],
"parameters": {
"kind": "vertical",
"final_state": "the row's orbital hole: 1t2^-1 (X 2T2, Jahn-Teller maxima) or 2a1^-1 (2A1)"
},
"uncertainty": {
"absolute": 0.1,
"level": "not stated"
}
}
p. 2218, CH4 column: band maxima I^m ~ vertical ionisation energies. Rows 1t2_1, 1t2_2, 1t2_3: the three maxima (13.6, 14.4, 15.0 eV) of the Jahn-Teller distorted 2T2 band (footnote a), the ionisation of the 1t2 orbital to CH4+ X 2T2; row 2a1: 22.9 eV, the 2a1^-1 (2A1) band. Accuracy +-0.1 eV (legend). Reference [17] for the whole column (record notes). The rows 1t2_1 to 1t2_3 equal heilbronner_1977/vertical_CH4 (TC-547). The 2a1 row (22.9 eV) is not in Heilbronner et al. 1977, whose spectra end near 21 eV: its origin is unknown.
bieri_1977/adiabatic_CH4#
{
"id": "adiabatic_CH4",
"material": "CH4",
"table": "text",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "reproduced",
"reproduced_from": [
"E. Heilbronner, T. B. Jones and J. P. Maier, Helv. Chim. Acta 60, 1697 (1977)"
],
"parameters": {
"kind": "adiabatic",
"final_state": "the row's orbital hole: 1t2^-1 (X 2T2) or 2a1^-1 (2A1)"
},
"uncertainty": {
"absolute": 0.02,
"level": "not stated"
}
}
2 inline points in the source record.
Footnotes a and b of the Section A tables (p. 2222): ‘The adiabatic ionization potential is I_1^a = 12.75 eV’ (the 2T2 band) and ‘Adiabatic ionization energy I_1^a = 22.39 eV’ (the 2a1 band, footnote b of 22.9). Estimated accuracy of adiabatic values +-0.02 eV (legend, p. 2218). Attributed to the column’s reference [17], but neither value is in Heilbronner et al. 1977 (heilbronner_1977 prints no adiabatic energy; TC-547): their origin is unknown.
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.