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Triply-differential Cross Sections for Electron-impact Ionization of Helium in Presence of Laser Field

Author: JiShenTong
Tutor: ZhangChengHua
School: Liaoning University
Course: Atomic and Molecular Physics
Keywords: Scattering first Born approximation triply differential cross sections laser field
CLC: O562.5
Type: Master's thesis
Year: 2011
Downloads: 24
Quote: 0
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Abstract


Scattering is a method way which studying the distribution of electron in atom,and it is received more and more attention,especially the study of （e,2e）reaction in laser field.We study triply-differential cross sections for ionization Helium by electron impact in presence of a low-frequency laser field using the first Born approximation, and helium is taken as hydrogenlike atom. The field is assumed to be the pulse envelope and to be weak compared to the typical atomic field. We report the TDCS for coplanar kinematics at incident energy of 1000eV and ejected-electron energy of 5eV for a fixed scattering angles 3°,5°and 8°,with variety of the strength and direction of laser field. Significant changes are noted in the triply-differential cross sections by the application of the laser field.In field-free, we present our results for ionization of helium by electron impact at incident energy of 1000eV and ejected-electron energy of 5eV for a fixed scattering angles3°,5°and 7°, underθ1=3°, when effective charge increase, the triply differential cross sections has changed obvious, both binary peak and recoil peak are suppressed. Underθ1=5°, when effective charge increase, binary peak is suppressed, and recoil peak is almost not change. Underθ1=7°, binary peak is obvious suppressed, but recoil peak is enhanced.All case above, the distribution of triply differential cross sections has axis symmetry structure, while the phase position of binary peak and recoil peak has changed.From the outcome of the distribution of scattering election in （e,2e） reaction which is assisted in laser field, we can see laser field has changed the distribution of scattering section, when the direction of laser field （ε|→） is taken to be parallel to the momentum transfer of the incident electron, as increase the strength of laser field, binary peak is more enhanced and recoil peak is more suppressed. While the direction of laser field （ε|→） is taken to be anti-parallel to the momentum transfer of the incident electron, as increase the strength of laser field, binary peak is suppressed and recoil peak is enhanced. Both those case, laser field has not broken the symmetry of angular distribution of the triple differential cross section.The direction of laser field （ε|→） is taken to be parallel or vertical to the momentum of the incident electron, as increase the strength of laser field, both binary peak and recoil peak become more complex change, under this case, laser field has broken the symmetry of angular distribution of the triple differential cross section.

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CLC: > Mathematical sciences and chemical > Physics > Molecular physics, atomic physics > Atomic Physics > Collisions and scattering
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