heilbronner_1977#
E. Heilbronner, T. B. Jones and J. P. Maier, “The Ionization Energies of Di-n-Alkyl Diacetylenes”, Helv. Chim. Acta 60, 1697 (1977)
Source record · Catalogue · Review register
Source kind: measurement
Recorded technique: He(I alpha) photoelectron spectroscopy, resolution E/Delta E ~ 200 (p. 1697), of the dialkyl diacetylenes R-(C#C)2-R (R = CH3, C2H5, n-C3H7, n-C4H9) and of the corresponding alkanes RH, ‘recorded on the same spectrometer and under comparable conditions’ (p. 1699). The calibration is not described.
Materials in structured entries: CH4
Dataset quantities: ionization_energy
Contents: 1 dataset; 0 formulas.
Curation notes#
PDF pages 1-4 = journal pages 1697-1700. Identity checked on the first page: this is the paper requested as the source of CH4’s vertical ionisation energy (Heilbronner, Jones & Maier, Helv. Chim. Acta 60, 1697 (1977)), and the paper bieri_1977 cites as its reference [17] for the whole CH4 column. Although the paper is about di-n-alkyl diacetylenes, CH4 does appear: its He(I) spectrum is superimposed on that of dimethyl diacetylene in Fig. 1 (p. 1698), and Table 2 (p. 1700) lists its sigma-type ionisation energies.
EXTRACTED: Table 2 (p. 1700, tbl_d6b9168f4f46, image checked), ‘Comparison of sigma-Type Ionization Energies of R-C#C-C#C-R with those of the corresponding Hydrocarbons (all values +- 0.1 eV)’, the CH4 column: 13.6, 14.4, 15.0 eV. These are the three maxima of CH4’s first band, the Jahn-Teller split 1t2^-1 (2T2) band (the spectrum in Fig. 1 shows maxima near 13.6 and 14.4 eV and a shoulder near 15 eV; the band’s onset lies near 12.7-13 eV). The paper does not call them maxima or vertical energies in so many words; Bieri, Burger, Heilbronner & Maier (bieri_1977, the same laboratory, the same year) reprint the three numbers as ‘band maxima of Jahn-Teller distorted 2T_d-band’, which by their legend are vertical ionisation energies. Recorded as vertical on that reading. The spectra ‘agree completely with those recorded by Price, Potts & Streets [9]’ (p. 1699).
NOT IN THIS PAPER: bieri_1977 attributes to this reference also CH4’s 2a1 band maximum (22.9 eV) and the adiabatic energies 12.75 eV (1t2) and 22.39 eV (2a1). None of them is here: the spectra of Fig. 1 end at about 21 eV (CH4’s at about 17 eV), the paper discusses only the window 12.5-17 eV (p. 1699), and it prints no adiabatic energy of CH4. bieri_1977’s attribution of the whole column to [17] follows its own legend’s rule, and is wrong for those three values.
COMPARISON: bieri_1977/vertical_CH4 rows 1t2_1-1t2_3 (13.6, 14.4, 15.0 eV, +-0.1 eV) are identical to this paper’s.
NOT EXTRACTED (out of scope): Table 1 (p. 1699), the X 2Pi_g and A 2Pi_u ionisation energies of diacetylene (R = H, 10.17 and 12.62 eV, from Baker & Turner [1]) and of the four dialkyl diacetylenes (the 0 <- 0 components, ‘close enough to the vertical ones’), with their shifts and splits (2.45 +- 0.05 eV); Table 2’s other columns (C2H6, C3H8, n-C4H10 and the alkyl groups of the diacetylenes; the C3H8 row 16.0 prints ‘0.2)c)’ with the opening parenthesis missing); the emission-spectrum splits of [8] (p. 1699); Fig. 1 (spectra, not digitised).
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
heilbronner_1977/vertical_CH4#
{
"id": "vertical_CH4",
"material": "CH4",
"file": "CH4/heilbronner_1977__vertical_CH4.csv",
"table": "tbl_d6b9168f4f46",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"kind": "vertical",
"final_state": "CH4+ X 2T2 (1t2^-1), Jahn-Teller components"
},
"uncertainty": {
"absolute": 0.1,
"level": "not stated"
}
}
Table 2, CH4 column, p. 1700: the three maxima of the Jahn-Teller split 1t2^-1 band (rows 1t2_1 to 1t2_3, as bieri_1977 labels them), ‘all values +- 0.1 eV’ (the caption; level not stated). The first, 13.6 eV, is the value the NIST WebBook lists as CH4’s vertical ionisation energy (via bieri_1977). Vertical by the reading in the record notes.
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.