Ionization Potentials of Molecules and Free Radicals and Appearance Potentials by Electron Impact in the Mass Spectrometer

Williams, James M.; Hamill, William H.

doi:10.1063/1.1669899

Cited by 80 publications

(32 citation statements)

References 24 publications

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“…The present experimental onset could only be compared with the measurement reported by Tsuda et al [33] at 10.7 eV or Williams and Hamill [41] at 9.60 ± 0.05 eV by electron impact. Using the ab initio calculated dissociation limit (see Section 3.3) of 12.705 eV for the reaction CH 3 + + Br and subtracting the electron affinity of the Br atom EA(Br) = 3.365 ± 0.003 eV [42] a threshold AE(CH 3 + /Br -) = 9.340 ± 0.003 eV is calculated.…”

Section: The Chf Fragment Ion (See Figs 5(b) and 6)mentioning

confidence: 67%

About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

et al. 2006

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The threshold photoelectron (TPES) and the photoionization mass spectrometric study of CH 3 Br in the 8-20 eV photon energy range is presented. The interpretation and assignments are supported by ab initio calculations. The TPES shows several new discrete features in the Jahn-Teller split ground state X 2 E( 2 A'-2 A") of CH 3 Br + . An additional continuous band starts at about 11.8 eV. These observations are both correlated with direct ionization and autoionizing transitions. This is supported by constant ion state (CIS) spectroscopy. A large enhancement of the transitions to the A 2 A and B E states is ascribed to important autoionizing contributions. Based on the present calculations, the weak to very weak bands in the 17.5-22.0 eV photon energy range were mainly assigned to 2a 1 -1 ionization and to double excitations described essentially by the 2e -2 4a 1 1 and le -1 2e -1 4a 1 1 configurations. The photoionization mass spectrometric study allowed us to investigate in detail the ionization and dissociation of CH 3 Br + leading to CH 2 + , CH 3 + , Br + and CH 2 Br + from threshold up to 20 eV photon energy. The experimental data are compared to ab initio dissociation energies. At the onset, the CH 3 + and CH 2 Br + fragment ion production is correlated with the ground state of CH 3 Br + and both fragment ions have to appear through dissociative autoionization from the (3a 1 1 /1e 3 )6s or 5s Rydberg state. This interpretation is supported by the photoabsorption spectrum measured recently in the same photon energy range. At higher energies, beside a likely direct (pre)dissociation of the Ã 2 A 1 and B 2 E states of CH 3 Br + , autoionization also contributes to the fragmentation in all decay channels. Avoided crossings in a manifold of 2 A' states are likely to be involved. This is supported by ab initio calculations. For CH 3 + the photoion-pair process is analyzed and detailed assignments are proposed on the basis of our latest VUV photoabsorption spectroscopic data.

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Section: The Chf Fragment Ion (See Figs 5(b) and 6)mentioning

confidence: 67%

About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

et al. 2006

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“…Rejoub et al [18] measured absolute partial and total cross sections, for electronimpact ionization of 1-propanol from threshold to 1000 eV, for groups of cations with similar mass, by using a time-of-flight mass spectrometer. Finally, Williams and Hamill [22] measured AEs and bond dissociative energies for 1-propanol using a retarding potential difference (RPD) method in their mass spectrometer. They found the onsets for production of the C3H7O + cation (m=59 amu) at 10.93 eV and a slope change at 14.07 eV.…”

Section: Introductionmentioning

confidence: 99%

Electron impact ionization of 1-propanol

Pires

Nixon

Ghosh

et al. 2017

International Journal of Mass Spectrometry

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.  Appearance energies and Wannier exponents for 16 formed cations were determined.  Theoretical BEB and IAM-SCAR and experimental total ionization cross sections are reported.

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“…There are not any published experimental photoelectron and authentic photoionization spectra of DIPE for comparison. Williams et al . assigned an ionization energy of 9.16 eV for DIPE, whereas Watanabe et al .…”

Section: Resultsmentioning

confidence: 99%

“…The corresponding Gibbs activation energy for this path is calculated to be 87 kJ mol −1 at room temperature, while the Gibbs reaction energy is −19 kJ mol −1 . In addition, William and Hamill found m/z=59 ascribed to 1‐methyl ethoxy radical generated by passing DIPE gas through a platinum wire “cracker”. The relative AIE was 9.20±0.05 eV, although we measure an onset at 9.60±0.05 eV.…”

Section: Resultsmentioning

confidence: 99%

Synchrotron Photoionization Study of the Diisopropyl Ether Oxidation

Giustini

Meloni

2020

ChemPhysChem

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Scientific evidence has shown oxygenates help to reduce dangerous pollutants arising from burning fossil fuel in the automotive sector. For this reason, their use as additives has spread widely. The aim of this work consists in providing a comprehensive identification of the main primary oxidation products of diisopropyl ether (DIPE), one of the most promising among etheric oxygenates. The Cl‐initiated oxidation of DIPE is examinated by using a vacuum ultraviolet (VUV) synchrotron radiation at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). Products are identified on the basis of their mass‐to‐charge ratio, shape of photoionization spectra, adiabatic ionization energies, and chemical kinetic profiles, at three different temperatures (298, 550, and 650 K). Acetone, propanal, propene, and isopropyl acetate have been identified as major reaction products. Acetone is the main primary product. Theoretical calculations using the composite CBS‐QB3 method provided useful tools to validate the postulated reaction mechanisms leading to experimentally observed species. The formation of other species is also discussed.

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Ionization Potentials of Molecules and Free Radicals and Appearance Potentials by Electron Impact in the Mass Spectrometer

Cited by 80 publications

References 24 publications

About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

Electron impact ionization of 1-propanol

Synchrotron Photoionization Study of the Diisopropyl Ether Oxidation

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