Photofragmentation of Halogenated Pyrimidine Molecules in the VUV Range

Abstract

In the present work, we studied the photoinduced ion chemistry of the halogenated pyrimidines, a class of prototype radiosensitizing molecules, in the energy region 9-15 eV. The work was stimulated by previous studies on inner shell site-selective fragmentation of the pyrimidine molecule, which have shown that the fragmentation is governed by the population/formation of specific ionic states with a hole in valence orbitals, which in turn correlate to accessible dissociation limits. The combined experimental and theoretical study of the appearance energies of the main fragments provides information on the geometric structure of the products and on the role played by the specific halogen atom and the site of halogenation in the dissociation process. This information can be used to gain new insights on the elementary mechanisms that could possibly explain the enhanced radiation damage to the DNA bases or to the medium in which the bases are embedded, thereby contributing to their radiosensitizing effect.

HSO2+ Formation from Ion‐Molecule Reactions of SO2⋅+ with Water and Methane: Two Fast Reactions with Reverse Temperature‐Dependent Kinetic Trend

“…The apparatus and the well-established experimental procedure are described in detail elsewhere. [27,28]…”

The Reaction of Sulfur Dioxide Radical Cation with Hydrogen and Its Relevance in Solar Geoengineering Models

“…The description of the CiPo beamline at ELETTRA has been reported previously. [50,[72][73][74][75][76] Briefly, the beamline is equipped with an electromagnetic elliptical undulator/wiggler and a Normal Incidence Monochromator (NIM) to cover the vacuum ultraviolet (VUV) 8-40 eV energy range. The aluminum grating of the NIM operates in the energy range 8-17 eV with a resolving power of about 1000.…”

Photoionization mass spectrometry of ω-phenylalkylamines: Role of radical cation-π interaction

“…Previous studies combining an experimental and theoretical survey of appearance energies (AEs) have provided valuable information on specific effects due to varying structures. 21 A similar approach, based on a VUV synchrotron beamline, is pursued in the present contribution.…”

“…A detailed overview of the instrumental apparatus is reported in previous studies. 21,23 Photoionization efficiency curves (PECs) for the selected ions were obtained from 7 to 15 eV of photon energy scanned in steps of 20 meV with an acquisition time of about 1 to 5 s/point, depending on the intensity of the assayed ion. Photon fluency was measured during each run employing a photodiode in order to normalize the PECs.…”

“…This difference is absolutely reasonable since we expect that the experimental IEs will be closer to the theoretical adiabatic values than to the vertical ones. 21 Table III reports the adiabatic IEs representing the energy difference between each neutral conformer and the corresponding optimized radical cation, whose geometries are depicted in Fig. 4.…”