Structure of electron tracks in water.  1.  Distribution of energy deposition events

Pimblott, Simon M.; LaVerne, Jay A.; Mozumder, A.; Green, Nicholas J. B.

doi:10.1021/j100364a084

Cited by 110 publications

(69 citation statements)

References 3 publications

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“…Both interactions are well above the previously mentioned threshold (e.g. Hamm et al 1985;Pimblott et al 1990;Dingfelder et al 2000;Plante & Cucinotta 2008). The average energy lost per collision is higher than these values.…”

Section: The Existence Of a Threshold Energysupporting

confidence: 65%

Swift heavy ion irradiation of water ice from MeV to GeV energies

Dartois

Ding

Barros

et al. 2013

A&A

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Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested. Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power. Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA. Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model. Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.

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Section: The Existence Of a Threshold Energysupporting

confidence: 65%

Swift heavy ion irradiation of water ice from MeV to GeV energies

Dartois

Ding

Barros

et al. 2013

A&A

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“…By combining the working model, reactions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), with the product yields in Tables 1 and 2, one can check to see if there is a reasonable balance between holes consumed and electrons consumed in product formation. The yields of products due to oxidation clearly exceeded those due to reduction, i.e., G ′ noE (SSB) + G ′ Fpg (SSB) > G ′ Nth (SSB).…”

Section: Balance Between Hole Consumption and Electron Consumptionmentioning

confidence: 99%

“…These are (1) spurs: <100 eV in a sphere, (2) blobs: 100 to 500 eV in a sphere or ellipsoid, and (3) short tracks: 500 to 5000 eV in a cylinder (6). The ratio for energy partitioning between these components, based on computational methods applied to water (7), is 0.75:0.12:0.13, respectively. Of importance here is the fact that the initial events are laid down in clusters (8) and that some sense of cluster size can be taken from the diameter of a spur in water, for which estimates range from 2 nm to 5 nm (9).…”

Section: Introductionmentioning

confidence: 99%

On the Chemical Yield of Base Lesions, Strand Breaks, and Clustered Damage Generated in Plasmid DNA by the Direct Effect of X Rays

2007

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The purpose of this study was to determine the yield of DNA base damages, deoxyribose damage, and clustered lesions due to the direct effects of ionizing radiation and to compare these with the yield of DNA trapped radicals measured previously in the same pUC18 plasmid. The plasmids were prepared as films hydrated in the range 2.5 < Γ < 22.5 mol water/mol nucleotide. Single-strand breaks (SSBs) and double-strand breaks (DSBs) were detected by agarose gel electrophoresis. Specific types of base lesions were converted into SSBs and DSBs using the base-excision repair enzymes endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The yield of base damage detected by this method displayed a strikingly different dependence on the level of hydration (Γ) compared with that for the yield of DNA trapped radicals; the former decreased by 3.2 times as Γ was varied from 2.5 to 22.5 and the later increased by 2.4 times over the same range. To explain this divergence, we propose that SSB yields produced in plasmid DNA by the direct effect cannot be analyzed properly with a Poisson process that assumes an average of one strand break per plasmid and neglects the possibility of a single track producing multiple SSBs within a plasmid. The yields of DSBs, on the other hand, are consistent with changes in free radical trapping as a function of hydration. Consequently, the composition of these clusters could be quantified. Deoxyribose damage on each of the two opposing strands occurs with a yield of 3.5 ± 0.5 nmol/J for fully hydrated pUC18, comparable to the yield of 4.1 ± 0.9 nmol/J for DSBs derived from opposed damages in which at least one of the sites is a damaged base.

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“…It has been assumed that the maximal free radical yield in DNA (that obtained if all ionizations are trapped as radicals) is roughly equivalent to the initial free radical yield in water (19,24) since the stopping power of DNA is similar to that of water (35,36). The initial free radical yield in water is estimated to be 1.18 µmol/J (37).…”

Section: Absolute Values Of Free Radical Yieldsmentioning

confidence: 99%

The Influence of Packing on Free Radical Yields in Solid-State DNA: Film Compared to Lyophilized Frozen Solution

Milano¹,

Bernhard²

1999

Radiation Research

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Radiation-induced free radical damage in solid-state DNA arises from direct-type damage mechanisms. In the present study, free radical yields in film and lyophilized Na DNA model systems are compared. The free radical yields in lyophilized samples are significantly greater than those in films. Since DNA conformation cannot account for the differences in free radical yields between different DNA preparations, it is proposed that the intermolecular spacing of DNA is a critical variable. The differences in the hydration dependence of free radical yields between the film and lyophilized DNA model systems are consistent with this thesis. The relatively large free radical yields observed in lyophilized DNA emphasize the fact that DNA is an extremely effective electron and hole scavenger, more so than previously thought.

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Structure of electron tracks in water. 1. Distribution of energy deposition events

Cited by 110 publications

References 3 publications

Swift heavy ion irradiation of water ice from MeV to GeV energies

Swift heavy ion irradiation of water ice from MeV to GeV energies

On the Chemical Yield of Base Lesions, Strand Breaks, and Clustered Damage Generated in Plasmid DNA by the Direct Effect of X Rays

The Influence of Packing on Free Radical Yields in Solid-State DNA: Film Compared to Lyophilized Frozen Solution

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