Differential cross sections for electron impact excitation of the<i>n</i>= 2 states of helium at intermediate energies (80, 100 and 120 eV) measured across the complete angular scattering range (0–180°)

Ward, Rupert; Cubric, D; Bowring, Nicholas; King, G C; Read, F H; Fursa, Dmitry V.; Bray, Igor; Zatsarinny, Oleg; Bartschat, Klaus

doi:10.1088/0953-4075/44/4/045209

Cited by 11 publications

(6 citation statements)

References 33 publications

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“…The summed DCS data were renormalized using the inelastic energy-loss signal of the n = 2 states of He [16] to correct for any transmission effects. While the He results of Trajmar et al [16] were utilized in the present work, more recent data show good agreement [17,18]. The measured spectra were unfolded, leaving all vibrational levels of the…”

Section: Experimental Methodsmentioning

confidence: 62%

Tuning out vibrational levels in molecular electron energy-loss spectra

et al. 2012

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The phenomenon whereby features associated with certain vibrational levels in molecular states of mixed electronic character disappear under specific scattering conditions in electron energy-loss spectra is investigated. In particular, using a combination of experimental measurements and coupled-channel calculations, anomalous vibrational intensities in the mixed valence-Rydberg 1 u ← X 1 + g transition of N 2 are explained. A single parameter, i.e., the ratio of the generalized electronic transition moments to the diabatic valence and Rydberg components of the mixed states, dependent on the experimental scattering conditions, is found to be essentially capable of describing all observed relative vibrational intensities, including the near disappearance of the b 1 u (v = 5) feature for momentum-transfer-squared values K 2 ≈ 0.3 a.u. This result highlights the interesting possibility of experimental control of molecular quantum-interference effects in electron energy-loss spectra, something that is not possible in optical spectra.

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Section: Experimental Methodsmentioning

confidence: 62%

Tuning out vibrational levels in molecular electron energy-loss spectra

et al. 2012

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“…For decreasing k D , we observe an increase in the transition probability magnitude. All maxima are located in the momentum transfer q interval [1,2] and have approximately the same position. At large values of the momentum transfer, the transition probability tends to zero, which is due to the variation of the radial wave functions for high atomic electron radius.…”

Section: Resultsmentioning

confidence: 89%

“…Electron impact excitation processes of the free helium [1][2][3][4] atom have been widely investigated in previous years. Electrons scattering processes are very important for both gas discharges, laser systems, fusion plasmas, etc.…”

Section: Introductionmentioning

confidence: 99%

Electron impact excitation of helium in Debye plasma

et al. 2015

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The probability, differential, and integral scattering cross sections of the 11S→21S and 11S→21P transitions of helium have been calculated in the first Born approximation. The projectile-target interactions depending on the temperature and the density of plasma are described by the Debye-Hückel model. Wave functions of the target before and after collision were modeled by non orthogonal Hartree-Fock orbitals. The wave functions parameters are calculated with the Ritz variational method. We improve our unscreened first Born approximation integral cross sections by using the BE-scaled (B stands for binding energy and E excitation energy) method. The second Born approximation has also been used to calculate the excitation cross sections in Debye plasma. Our calculations are compared to other theoretical and experimental results where applicable.

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“…Once data was obtained, this was normalized against a known cross section, to calculate the differential cross section values. This technique has been used successfully previously to demonstrate independent agreement between a range of experimental and advanced theoretical models [47]. In this study the differential cross section of the 2 1 P state was chosen as the reference using values obtained using the converging close-coupling method [48].…”

Section: Apparatus and Experimental Proceduresmentioning

confidence: 99%

Negative ion resonance measurements in the autoionizing region of helium measured across the complete angular scattering range (0°–180°)

Ward¹,

Cubric²,

Bowring³

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Excitation function measurements for the decay of the 2s 2 2p 2 P and 2s2p 2 2 D triply excited negative ion resonances in helium to singly excited n=2 states have been measured. These excitation functions have been determined across the complete angular range (0-180°) using a magnetic angle changer (MAC) with a soft-iron core. The convergent close-coupling method has been used to calculate the cross sections, with the underlying complexity of the problem not yet being able to be fully resolved. Agreement between the present experimental data and previous experimental data is good, with these excitation functions confirming the presence of an unusual (2s 2 2p)

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Differential cross sections for electron impact excitation of then= 2 states of helium at intermediate energies (80, 100 and 120 eV) measured across the complete angular scattering range (0–180°)

Cited by 11 publications

References 33 publications

Tuning out vibrational levels in molecular electron energy-loss spectra

Tuning out vibrational levels in molecular electron energy-loss spectra

Electron impact excitation of helium in Debye plasma

Negative ion resonance measurements in the autoionizing region of helium measured across the complete angular scattering range (0°–180°)

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