Remarks by David A. Colson

Colson, David A.

doi:10.1017/s0272503700007199

Cited by 2 publications

(3 citation statements)

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“…One should be aware of the fact that a considerable amount of computational results have been reported on the deoxyribose radical, the radical cations, and some structurally related compounds by looking at radical stability, charge localization, and charge transfer following DNA irradiation. ,, Furthermore, the minimum energy conformations of the ribose and the ribose radicals from H-abstraction were determined from the ab initio method with a small preference for H abstraction from the C adjacent to the alicyclic O observed for the furanose ring . Additional theoretical investigations have also looked at several properties of a variety of DNA components, like electron affinities, ionization energies, etc., also including the ribose and deoxyribose fragments. − …”

Section: Resultsmentioning

confidence: 99%

“…The nanoscopic mechanism which has reached by now a rather broad consensus in the relevant literature − involves the initial removal of electrons from the molecular components of the complex network by the impinging radiation. Such electrons originate from either the valence levels of the chemical bonds or from the localized inner shells of the atomic components . Secondary electrons with initial kinetic energies up to about 20 eV turn out to be indeed the most abundant of the secondary species created by the primary ionizing radiation .…”

Section: Introductionmentioning

confidence: 99%

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Selective Bond Breaking in β-d-Ribose by Gas-Phase Electron Attachment around 8 eV

et al. 2007

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Electron attachment experiments are carried out on the beta-d-ribose molecule in the gas phase for the energy region around 8 eV, and clear fragmentation products are observed for different mass values. A computational analysis of the relevant dynamics is also carried out for the beta-d-ribose in both the furanosic and pyranosic form as gaseous targets around that energy range. The quantum scattering attributes obtained from the calculations reveal in both systems the presence of transient negative ions (TNIs). An analysis of the spatial features of the excess resonant electron, together with the computation and characterization of the target molecular normal modes, suggests possible break-up pathways of the initial, metastable molecular species.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Selective Bond Breaking in β-d-Ribose by Gas-Phase Electron Attachment around 8 eV

et al. 2007

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“…For example, by lowering g, the laser energy at saturation decreases, which inhibits the sideband generation. 9 Then, this restrains the spectrum broadening since the DFG depends on the energy level of the fundamental mode and its sideband. The DFG processes are a complementary interpretation to the usual assumption of additional secondorder sidebands to justify the expected transition 9 from chaotic to nonchaotic spectra when cavity losses increase.…”

Section: ± M(co S -Of)mentioning

confidence: 99%

Stability of a free-electron-laser spectrum in the continuous-beam limit

Iracane

Ferrer

1991

Phys. Rev. Lett.

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A multifrequency model is developed for a Compton free-electron laser and is solved to investigate the continuous-electron-beam limit. Both numerical simulations and perturbation expansions allow us to exhibit a mechanism leading to the broadening of the spectrum. Then, the nonlinear asymptotic behavior of the spectrum is analyzed.PACS numbers: 42.55.Tb, 52.35.Mw One of the most challenging questions in freeelectron-laser (FEL) physics is related to the nonlinear evolution of the spectrum, including the sideband instability 1_3 and mode competition (MC). 4 New nonlinear effects can alter the further evolution of a FEL spectrum, especially in the asymptotic regime which corresponds to a large number of round trips for an oscillator. Of course, optical elements can select a single frequency, 5 but we are concerned here with the natural physical evolution of the spectrum in the absence of frequency discrimination. Moreover, we focus on the limit of a continuous electron beam, which means that finite-pulse issues, such as the natural Fourier spread or temporal overlap effects, are disregarded.In the continuous-beam limit (CBL), our numerical simulations exhibit the following essential property: Any spectral pattern, for instance, two frequencies with the same amplitude, can duplicate itself. We confirm this numerical prediction by expanding the multifrequency model with two different perturbation theories. Then, the nonlinear evolution of the spectrum is investigated by means of computer simulations. We observe some expected results, such as the transition between narrow and broad spectra depending upon the electronic current or the cavity losses. A more challenging numerical prediction in the saturation regime is a scaling law between the spectral width and the extracted efficiency.To investigate the FEL spectral dynamics, we use a specific model for the CBL which is appropriate for electronic pulses much longer than the slippage distance. 6 To work out this model, we expand the laser field A L as the product of rapid phases and slowly varying envelopes S"iz): S"(z)where k n =(\+n/N)kL is a wave number close to the central mode /cz, = 27rAz,. Each complex laser field S" J satisfies a paraxial equation: n/N)k H w z G n -^Q--a w e 2Kwhere a w and k w are the normalized amplitude and the wave number of the magnetic field. The longitudinal electronic distribution g(z,y/,y) satisfies the associated Vlasov equations:[3 z + v8 vr +r(8 y -l/y)]g(z,^y)-0, v-k w -(k L /2Y 2 Hl+ ja£) , F= J a w \m 2 &me(3) dy/J dyg(z,y/,y)mc=p e , 2TTNJOwhere p e is the electron number per unit of volume. The electron phase space is characterized x by the resonant phase y/^ikL + k^z -co L t and the kinetic energy y normalized to the electronic mass m. The variable y/ depends on the central frequency cot^ckL, but Eqs. (l)-(3) are invariant under the choice of co L when we consider the limit of the continuous Fourier expansion in , -i(\+n/N)y 2y(2)Eq. (1). Indeed, the phase (\+n/N)y/-(n/N)k w z, in Eqs. (2) and (3), is precisely the resonant ...

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Remarks by David A. Colson

Cited by 2 publications

References 0 publications

Selective Bond Breaking in β-d-Ribose by Gas-Phase Electron Attachment around 8 eV

Selective Bond Breaking in β-d-Ribose by Gas-Phase Electron Attachment around 8 eV

Stability of a free-electron-laser spectrum in the continuous-beam limit

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