## Abstract

This thesis describes an experimental study into the electron-impact excitation to the 3{sup 3}P, 3{sup 1}D and 3{sup 3}D states of Helium. The scattered electron and the photon, emitted by the excited atom, are measured in coincidence. The parameters, which can be varied, are the scattering angle and the kinetic energy of the projectile. Two parameters, which are used to characterize the excited state, are the angular momentum transferred to the atom, L perpendicular, and the alignment angle {gamma}. It is shown that results of measurements on 3{sup 1}D excitation with photon detection perpendicular to the scattering plane do not agree in the small scattering angle region with any of the model calculations currently available. Remarkable is the sign of L perpendicular, which appears to start of negatively at 60 eV. It is shown that for 3{sup 3}P excitation the predicted large value of {gamma} is indeed found experimentally. This supports the suggestion that exchange scattering is underestimated in model calculations for {sup 1}P excitation. Another result is that for {sup 1}P and {sup 3}P excitation the behaviour of L perpendicular as a function of the scattering angle can be related at different impact energies with the help of a
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## Citation Formats

Batelaan, Hermanus.
Coherence in electron-impact excitation of helium.
Netherlands: N. p.,
1991.
Web.

Batelaan, Hermanus.
Coherence in electron-impact excitation of helium.
Netherlands.

Batelaan, Hermanus.
1991.
"Coherence in electron-impact excitation of helium."
Netherlands.

@misc{etde_10111271,

title = {Coherence in electron-impact excitation of helium}

author = {Batelaan, Hermanus}

abstractNote = {This thesis describes an experimental study into the electron-impact excitation to the 3{sup 3}P, 3{sup 1}D and 3{sup 3}D states of Helium. The scattered electron and the photon, emitted by the excited atom, are measured in coincidence. The parameters, which can be varied, are the scattering angle and the kinetic energy of the projectile. Two parameters, which are used to characterize the excited state, are the angular momentum transferred to the atom, L perpendicular, and the alignment angle {gamma}. It is shown that results of measurements on 3{sup 1}D excitation with photon detection perpendicular to the scattering plane do not agree in the small scattering angle region with any of the model calculations currently available. Remarkable is the sign of L perpendicular, which appears to start of negatively at 60 eV. It is shown that for 3{sup 3}P excitation the predicted large value of {gamma} is indeed found experimentally. This supports the suggestion that exchange scattering is underestimated in model calculations for {sup 1}P excitation. Another result is that for {sup 1}P and {sup 3}P excitation the behaviour of L perpendicular as a function of the scattering angle can be related at different impact energies with the help of a partial wave expansion. A scaling relation can be formulated for the behaviour of L perpendicular. The influence of a negative ion resonance to excitation of the 3{sup 3}D state is investigated. Both in coincidence and non-coincidence measurements the presence of the resonance yields information on both the direct and indirect excitation of the 3{sup 3}D state. It is shown that the coincident measurement gives an unique opportunity to determine the excited 3{sup 3}D state completely. Results of measurements with photon detection in the scattering plane are given. They supplement previous 3{sup 1}D and 3{sup 3}D results and allow physical parameters, such as L perpendicular and {gamma}, to be obtained. (H.W.). 132 refs.; 20 figs.; 18 tabs.}

place = {Netherlands}

year = {1991}

month = {Jun}

}

title = {Coherence in electron-impact excitation of helium}

author = {Batelaan, Hermanus}

abstractNote = {This thesis describes an experimental study into the electron-impact excitation to the 3{sup 3}P, 3{sup 1}D and 3{sup 3}D states of Helium. The scattered electron and the photon, emitted by the excited atom, are measured in coincidence. The parameters, which can be varied, are the scattering angle and the kinetic energy of the projectile. Two parameters, which are used to characterize the excited state, are the angular momentum transferred to the atom, L perpendicular, and the alignment angle {gamma}. It is shown that results of measurements on 3{sup 1}D excitation with photon detection perpendicular to the scattering plane do not agree in the small scattering angle region with any of the model calculations currently available. Remarkable is the sign of L perpendicular, which appears to start of negatively at 60 eV. It is shown that for 3{sup 3}P excitation the predicted large value of {gamma} is indeed found experimentally. This supports the suggestion that exchange scattering is underestimated in model calculations for {sup 1}P excitation. Another result is that for {sup 1}P and {sup 3}P excitation the behaviour of L perpendicular as a function of the scattering angle can be related at different impact energies with the help of a partial wave expansion. A scaling relation can be formulated for the behaviour of L perpendicular. The influence of a negative ion resonance to excitation of the 3{sup 3}D state is investigated. Both in coincidence and non-coincidence measurements the presence of the resonance yields information on both the direct and indirect excitation of the 3{sup 3}D state. It is shown that the coincident measurement gives an unique opportunity to determine the excited 3{sup 3}D state completely. Results of measurements with photon detection in the scattering plane are given. They supplement previous 3{sup 1}D and 3{sup 3}D results and allow physical parameters, such as L perpendicular and {gamma}, to be obtained. (H.W.). 132 refs.; 20 figs.; 18 tabs.}

place = {Netherlands}

year = {1991}

month = {Jun}

}