Absolute cross sections for electronic excitation of pyrimidine by electron impact

Regeta, Khrystyna; Allan, Michael; Mašín, Zdeněk; Gorfinkiel, Jimena D.

doi:10.1063/1.4939077

Cited by 25 publications

(27 citation statements)

References 53 publications

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“…It is pronounced in cross sections for electronic excitation and will be discussed in the accompanying paper. 38 The shapes of the experimental cross sections as a function of energy from Fig. 5 were summed, with appropriate weights, as described in Ref.…”

Section: Dependence On Electron Energymentioning

confidence: 99%

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Regeta

Allan

Winstead

et al. 2016

The Journal of Chemical Physics

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Articles you may be interested inUnusual temperature dependence of the dissociative electron attachment cross section of 2-thiouracil J. Chem. Phys. 144, 034306 (2016) We measured differential cross sections for elastic (rotationally integrated) electron scattering on pyrimidine, both as a function of angle up to 180• at electron energies of 1, 5, 10, and 20 eV and as a function of electron energy in the range 0.1-14 eV. The experimental results are compared to the results of the fixed-nuclei Schwinger variational and R-matrix theoretical methods, which reproduce satisfactorily the magnitudes and shapes of the experimental cross sections. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. Resonant structures are observed at 0.2, 0.7, and 4.35 eV and calculations for different symmetries confirm their assignment as theX 2 A 2 ,Ã 2 B 1 , andB 2 B 1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering theB 2 B 1 shape resonance appears as a peak, a dip, or a step function in the cross sections recorded as a function of energy at different scattering angles and this effect is satisfactorily reproduced by theory. The dip and peak contributions at different scattering angles partially compensate, making the resonance nearly invisible in the integral cross section. Vibrationally integrated cross sections were also measured at 1, 5, 10 and 20 eV and the question of whether the fixed-nuclei cross sections should be compared to vibrationally elastic or vibrationally integrated cross section is discussed. C 2016 AIP Publishing LLC. [http://dx

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Section: Dependence On Electron Energymentioning

confidence: 99%

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Regeta

Allan

Winstead

et al. 2016

The Journal of Chemical Physics

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“…4). Indeed, "spin-forbidden" transitions are common upon electron impact and have been routinely used to study the spectroscopy of the corresponding excited states [64][65][66][67]. Ground state singlet-triplet energy gaps computed with spin-flip EOM-CCSD (EOM-SF-CCSD) [43,68,69] for neutral formamide are shown in Fig.…”

mentioning

confidence: 99%

Dipole-Supported Electronic Resonances Mediate Electron-Induced Amide Bond Cleavage

Ryszka

Dawley

et al. 2019

Phys. Rev. Lett.

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Dissociative electron attachment (DEA) plays a key role in radiation damage of biomolecules under high-energy radiation conditions. The initial step in DEA is often rationalized in terms of resonant electron capture into one of the metastable valence states of a molecule followed by its fragmentation. Our combined theoretical and experimental investigations indicate that the manifold of states responsible for electron capture in the DEA process can be dominated by core-excited (shake-up) dipole-supported resonances. Specifically, we present the results of experimental and computational studies of the gas-phase DEA to three prototypical peptide molecules, formamide, N-methylformamide (NMF), and N,N-dimethylformamide (DMF). In contrast to the case of electron capture by positively charged peptides in which amide bond rupture is rare compared to N-Cα bond cleavage, fragmentation of the amide bond was observed in each of these three molecules. The ion yield curves for ions resulting from this amide bond cleavage, such as NH 2 ⎯ for formamide, NHCH 3 ⎯ for NMF, and N(CH 3 ) 2 ⎯ for DMF, showed a double-peak structure in the region between 5 to 8 eV. The peaks are assigned to Feshbach resonances including core-excited dipole-supported resonances populated upon electron attachment based on the highlevel electronic structure calculations. Moreover, the lower energy peak is attributed to formation of the coreexcited resonance that correlates with the triplet state of the neutral molecule. The latter process highlights the role of spin-forbidden transitions promoted by electron impact in the DEA process.

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“…Figure 1 also shows an enhancement of the scattering cross section in the energy range 7-13 eV which is caused by a pair of overlapping resonances (identified asg 2 B 1 andx 2 B 1 in Ref. [15]). This higher energy enhancement is smooth and does not show a cut-off effect (nor does the experimental excitation function for 180…”

Section: Resultsmentioning

confidence: 99%

“…The effect these resonances have on the angular behaviour of the elastic cross section has not been investigated in detail. Recent experiments [14,15] have provided a very detailed analysis of both elastic and inelastic (mainly electronic excitation) electron scattering from pyrimidine: the determination of both differential and integral cross sections as well as excitation functions has enabled a thorough comparison with theory. An interesting feature in the excitation functions (angular differential cross sections plotted for a specific scattering angle as a function of scattering energy) is the presence of a peak/dip in the energy range of the third π * resonance [14].…”

Section: Introductionmentioning

confidence: 99%

Effect of the third π ∗ resonance on the angular distributions for electron-pyrimidine scattering

Mašín

Gorfinkiel

2016

Eur. Phys. J. D

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Abstract. We present a detailed analysis of the effect of the well known third π * resonance on the angular behaviour of the elastic cross section in electron scattering from pyrimidine. This resonance, occurring approximately at 4.7 eV, is of mixed shape and core-excited character. Experimental and theoretical results show the presence of a peak/dip behaviour in this energy range, that is absent for other resonances. Our investigations show that the cause of the peak/dip is an interference of background p-wave to p-wave scattering amplitudes with the amplitudes for resonant scattering. The equivalent resonance in pyrazine shows the same behaviour and the effect is therefore likely to appear in other benzene-like molecules.

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Absolute cross sections for electronic excitation of pyrimidine by electron impact

Cited by 25 publications

References 53 publications

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory

Dipole-Supported Electronic Resonances Mediate Electron-Induced Amide Bond Cleavage

Effect of the third π ∗ resonance on the angular distributions for electron-pyrimidine scattering

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