The complete optical spectrum of liquid water measured by inelastic x-ray scattering

Hayashi, Hisashi; Watanabe, Noboru; Udagawa, Yasuo; Kao, C.‐C.

doi:10.1073/pnas.110572097

Cited by 184 publications

(154 citation statements)

References 17 publications

(21 reference statements)

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“…In general, ǫ(E, k) = ǫ 1 (E, k) + iǫ 2 (E, k), where both the real part ǫ 1 and the imaginary part ǫ 2 are derivable from experiments [33]. They are shown in Fig.…”

Section: A the Dielectric Response Model: Optical Approximationmentioning

confidence: 99%

Spectra of secondary electrons generated in water by energetic ions

2010

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The energy distributions of secondary electrons produced by energetic carbon ions (in the energy range used, e.g., in hadron therapy) , incident on liquid water, are discussed. For low-energy ions, a new parameterization of the singly-differential ionization cross sections is introduced, based on tuning the position of the Bragg peak. The resulting parameterization allows a fast calculation of the energy spectra of secondary electrons at different depths along the ion's trajectory, especially near the Bragg peak. At the same time, this parameterization provides penetration depths for a broad range of initial-ion energies within the therapeutically-accepted error. For high-energy ions, the energy distribution is obtained with a use of the dielectric response function approach.Different models are compared and discussed. *

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“…In general, ǫ(E, k) = ǫ 1 (E, k) + iǫ 2 (E, k), where both the real part ǫ 1 and the imaginary part ǫ 2 are derivable from experiments [33]. They are shown in Fig.…”

Section: A the Dielectric Response Model: Optical Approximationmentioning

confidence: 99%

Spectra of secondary electrons generated in water by energetic ions

2010

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“…A broad range of energies play a role in the radiolysis of liquid water, due to the nonselective nature of the excitation process and the broad energy loss spectrum that peaks near 22 eV and extends above 100 eV. 59 Electrons from primary ionization events with more than about 8 -10 eV of excess energy ionize additional water molecules, leading to a high concentration of ionization events in relatively close proximity. Electrons that do not have sufficient energy to ionize additional water molecules ͑"subexcitation" electrons͒ instead relax by transferring energy into vibrations, rotations, and collective modes of the solvent until they lose enough energy to become trapped.…”

Section: Isotope Dependence Of the Ejection Lengthmentioning

confidence: 99%

Excitation-energy dependence of the mechanism for two-photon ionization of liquid H2O and D2O from 8.3to12.4eV

Elles

Jailaubekov

Crowell

et al. 2006

The Journal of Chemical Physics

119

192

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Transient absorption measurements monitor the geminate recombination kinetics of solvated electrons following two-photon ionization of liquid water at several excitation energies in the range from 8.3 to 12.4 eV. Modeling the kinetics of the electron reveals its average ejection length from the hydronium ion and hydroxyl radical counterparts and thus provides insight into the ionization mechanism. The electron ejection length increases monotonically from roughly 0.9 nm at 8.3 eV to nearly 4 nm at 12.4 eV, with the increase taking place most rapidly above 9.5 eV. We connect our results with recent advances in the understanding of the electronic structure of liquid water and discuss the nature of the ionization mechanism as a function of excitation energy. The isotope dependence of the electron ejection length provides additional information about the ionization mechanism. The electron ejection length has a similar energy dependence for two-photon ionization of liquid D 2 O, but is consistently shorter than in H 2 O by about 0.3 nm across the wide range of excitation energies studied.

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“…In Fig. 1 we compare the experimentally determined optical ELF of four condensed organic compounds [20][21][22][23] with the results obtained through Eq. (2).…”

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confidence: 99%

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

et al. 2013

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We present a semiempirical model for calculating the electron emission from any organic compound after ion impact. With only the input of the density and composition of the target we are able to evaluate its ionization cross sections using plausible approximations. Results for protons impacting in the most representative biological targets (such as water or DNA components) show a very good comparison with experimental data. Because of its simplicity and great predictive effectiveness, the method can be immediately extended to any combination of biological target and charged particle of interest in ion beam cancer therapy. DOI: 10.1103/PhysRevLett.110.148104 PACS numbers: 87.53.Àj, 79.20.Àm, 87.14.gk, 87.56.Àv Secondary electron emission is a key step in the mechanism of radiation damage to biomolecular systems induced by ion impact. As a matter of fact, ion beam cancer therapy exploits the particular properties of ion tracks, in which the ionization yield reaches a maximum near the end of their trajectories (the Bragg peak), allowing a precise and narrow energy deposition in deep-seated tumors, minimizing the radiation effects in healthy surrounding tissues [1]. These ejected electrons can produce further ionizations, initiating an avalanche effect, leading to the energy transfer to sensitive biomolecular targets, such as DNA or proteins. But not only is the number of emitted electrons relevant, but also their energy spectrum, since, although high energy electrons are those capable of producing further ionizations, it has been shown that low energy electrons (below ionization threshold) can also produce damage to biomolecules by dissociative electron attachment [2,3].In order to reach a deeper understanding of ion beam cancer therapy from a fundamental point of view, a great amount of data is needed regarding several and very diverse processes, since the whole mechanism implies steps in very different energy, space, and time scales. Therefore, the problem must be studied within a multiscale approach [4], a fact that motivates an interdisciplinary effort within the European COST Action Nano-IBCT (Nanoscale insights into ion beam cancer therapy) to build a comprehensive database [5]. In this context, ionization data for a wide variety of projectile and organic target combinations, covering a broad range of incident and ejected energies, is needed in order to get insight into micro-and nanometric aspects of radiation damage to biomolecular systems. The aim of this Letter is to present a simple theoretical method that provides the above mentioned required ionization data with the use of little input information, based on the dielectric formalism [6] and some physically motivated approximations. Results are here presented for proton impact, although the methodology can be immediately extended to heavier ions, electrons, and other charged particles.Although several simple theoretical and semiempirical methods already exist nowadays to calculate the energy spectra of secondary electrons [7] (and are currently in us...

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The complete optical spectrum of liquid water measured by inelastic x-ray scattering

Cited by 184 publications

References 17 publications

Spectra of secondary electrons generated in water by energetic ions

Spectra of secondary electrons generated in water by energetic ions

Excitation-energy dependence of the mechanism for two-photon ionization of liquid H2O and D2O from 8.3to12.4eV

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

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