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 <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/heilbronner_1977.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.1002/hlca\.19770600525 <https://doi.org/10.1002/hlca.19770600525>`__

**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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "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 :doc:`review register </register>` for the checks and decisions.