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    Electron impact fragmentation of thymine: partial ionization cross sections for positive fragments


    van der Burgt, Peter J.M. and Mahon, Francis Anthony and Barrett, Gerard and Gradziel, Marcin (2014) Electron impact fragmentation of thymine: partial ionization cross sections for positive fragments. European Physical Journal D, 68 (151). ISSN 1434-6060

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    Abstract

    We have measured mass spectra for positive ions for low-energy electron impact on thymine using a reflectron time-of-flight mass spectrometer. Using computer controlled data acquisition, mass spectra have been acquired for electron impact energies up to 100 eV in steps of 0.5 eV. Ion yield curves for most of the fragment ions have been determined by fitting groups of adjacent peaks in the mass spectra with sequences of normalized Gaussians. The ion yield curves have been normalized by comparing the sum of the ion yields to the average of calculated total ionization cross sections. Appearance energies have been determined. The nearly equal appearance energies of 83 u and 55 u observed in the present work strongly indicate that near threshold the 55 u ion is formed directly by the breakage of two bonds in the ring, rather than from a successive loss of HNCO and CO from the parent ion. Likewise 54 u is not formed by CO loss from 82 u. The appearance energies are in a number of cases consistent with the loss of one or more hydrogen atoms from a heavier fragment, but 70 u is not formed by hydrogen loss from 71 u.

    Item Type: Article
    Additional Information: Cite this article as: van der Burgt, P., Mahon, F., Barrett, G. et al. Eur. Phys. J. D (2014) 68: 151. https://doi.org/10.1140/epjd/e2014-40699-0
    Keywords: Thymine; Ionization Cross Section; HNCO; Appearance Energy; Successive Loss;
    Academic Unit: Faculty of Science and Engineering > Electronic Engineering
    Item ID: 9797
    Identification Number: https://doi.org/10.1140/epjd/e2014-40699-0
    Depositing User: Dr. Marcin Lukasz Gradziel
    Date Deposited: 17 Aug 2018 16:32
    Journal or Publication Title: European Physical Journal D
    Publisher: Springer
    Refereed: Yes
    URI:

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