Absorption effects for electron-molecule collisions

Castro, Eduardo A.; Souza, Gabriel L. C. de; Iga, I.; Machado, L. E.; Brescansin, L. M.; Lee, M.-T.

doi:10.1016/j.elspec.2007.03.005

Cited by 21 publications

(25 citation statements)

References 53 publications

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“…At those energies the elastic DCSs are lowered due to the flux leakage to the now opened inelastic channels. This effect has also been obtained by using complex (absorption) potentials [55].…”

Section: Resultsmentioning

confidence: 99%

Electronic excitation of gas-phase furan molecules by electron impact

et al. 2012

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Experiments and ab-initio calculations of the differential and integral cross sections for the electronic excitation from the ground state 1 A 1 to the 3 B 2 and 3 A 1 states of gas-phase furan molecules, by low-energy electron impact, were performed. Experimental differential cross sections were measured at incident electron energies between 5 to 15 eV and for scattering angles from 10 • to 130 • . The calculated cross sections were obtained using the Schwinger multichannel method implemented with pseudopotentials. The influence of channel-coupling and polarization effects is investigated through the comparison between three different models of scattering calculations, each one considering a distinct channel-coupling scheme. The comparison of experimental and calculated cross sections for electronically inelastic electron scattering by C 4 H 4 O molecules is found to be mostly reasonable. The existing discrepancies in this combined theoretical and experimental study help to illustrate difficulties in readily establishing reliable electronic excitation cross sections of polyatomic molecules by low-energy electrons.PACS numbers: 34.80. Gs, 34.80.Bm I INTRODUCTIONElectron-induced breakage of chemical bonds through dissociative electron attachment, a process mediated by the formation of temporary anionic states, has been recognized as a very efficient mechanism leading to the production of permanent lesions on DNA chains in the form of single-and double-strand breaks [1][2][3][4][5]. Much of the latest ongoing work on this subject has been devoted to the study of inelastic processes, more specifically, those involving electronic and/or vibrational excitations of the DNA basic constituents by impact of lowenergy electrons [6][7][8][9][10][11]. In particular, the electronic excitation cross sections obtained in these studies revealed the presence of several core-excited resonances that appear at energies ranging typically from 5 eV to 10 eV. These findings are relevant because the formation of such short-lived negative ion states represents an alternative, and probably rather effective if compared to "one-particle" shape resonances, doorway for electron-induced damage to DNA. Thus, the determination of electronic excitation cross sections for biomolecules (such as the nitrogenous bases or the phosphate group) certainly represents a crucial step towards a deeper insight into the mechanisms of DNA damage by secondary electrons and establishes itself as a challenging task for experimentalists and theoreticians. On the experimental point of view, the difficulties for obtaining reliable cross sections are related to the resolution of the molecular spectra via energy loss assignments and widths of spectral features observed and also to the sensitivity of handling very low energy electrons in the electron spectrometer.From the theoretical perspective, there are also subtle aspects related to the description of such kind of processes, observed in applications involving relative small molecules with low-lying excited ...

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Section: Resultsmentioning

confidence: 99%

Electronic excitation of gas-phase furan molecules by electron impact

et al. 2012

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“…The use of model absorption potentials is presently the only practical manner for treating electron-molecule collisions in the intermediate-energy range [49]. In the present work, a modified version of the quasifree scattering model (QFSM) of Staszewska et al [50], known as the scaled quasifree scattering model (SQFSM) [49,51], is used to account for the absorption effects. The SQFSM has already been successfully applied to investigate electron collisions on several targets [49,[51][52][53][54][55].…”

Section: Theory and Calculationmentioning

confidence: 99%

“…In the present work, a modified version of the quasifree scattering model (QFSM) of Staszewska et al [50], known as the scaled quasifree scattering model (SQFSM) [49,51], is used to account for the absorption effects. The SQFSM has already been successfully applied to investigate electron collisions on several targets [49,[51][52][53][54][55]. Also recently, in a benchmark study Staszewska et al [56] confirmed the effectiveness of the SQFSM in describing electron-atom scattering.…”

Section: Theory and Calculationmentioning

confidence: 99%

Absorption effects in electron–sulfur-dioxide collisions

et al. 2011

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A joint experimental-theoretical study on electron-SO 2 collisions in the low and intermediate energy range is reported. More specifically, experimental elastic differential, integral, and momentum transfer cross sections in absolute scale are measured in the 100-1000 eV energy range using the relative-flow technique. Calculated elastic differential, integral, and momentum transfer cross sections as well as grand-total and total absorption cross sections are also presented in the 1-1000 eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics, whereas the Schwinger variational iterative method combined with the distorted-wave approximation is used to solve the scattering equations. Comparison of the present results is made with the theoretical and experimental results available in the literature.

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“…Therefore, several semiempirical model absorption potentials have been proposed and applied within the singlechannel framework [25,26]. Among them, the scaled quasifree-scattering model (SQFSM), which is an improvement of the quasi-free-scattering model version 3 (QFSM3) of Staszewska et al [27], was proposed by our group a few years ago [28,29]. In general, DCS, ICS, and MTCS calculated using the SQFSM for elastic electron-molecule scattering do not differ significantly from those computed using the QFSM3.…”

Section: Introductionmentioning

confidence: 99%

“…In general, DCS, ICS, and MTCS calculated using the SQFSM for elastic electron-molecule scattering do not differ significantly from those computed using the QFSM3. However, for a variety of atomic and molecular targets [29][30][31], the agreement between the TCS and total absorption cross sections (TACS) calculated with the SQFSM and the corresponding experimental data is significantly better than the agreement with their QFSM3 counterparts. This improvement was confirmed by a recent benchmark study of Staszewska et al [32] for electron-atom collisions.…”

Section: Introductionmentioning

confidence: 99%

Cross sections for electron scattering by formaldehyde and pyrimidine in the low- and intermediate-energy ranges

Ferraz

Santos

Souza³

et al. 2013

Phys. Rev. A

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We report a theoretical study on electron scattering by two strongly polar molecules, namely, formaldehyde (CH 2 O) and pyrimidine (C 4 H 4 N 2 ), in the low-and intermediate-energy ranges. Calculated elastic differential, integral, and momentum-transfer cross sections, as well as total (elastic + inelastic) and total absorption cross sections, are reported for impact energies ranging from 0.2 to 500 eV. A complex optical potential is used to represent the electron-molecule interaction dynamics, whereas a single-center-expansion method associated with the Padé approximant technique is used to solve the scattering equations. Our calculated results are compared with experimental results and other theoretical data available in the literature. Generally good agreement is seen in these comparisons.

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Absorption effects for electron-molecule collisions

Cited by 21 publications

References 53 publications

Electronic excitation of gas-phase furan molecules by electron impact

Electronic excitation of gas-phase furan molecules by electron impact

Absorption effects in electron–sulfur-dioxide collisions

Cross sections for electron scattering by formaldehyde and pyrimidine in the low- and intermediate-energy ranges

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