Electron impact excitation of helium atom

Abstract

A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation (FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method, the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.

An effective method to calculate the electron impact excitation cross sections of helium from ground state to a final channel in the whole energy region

“…In our previous work, [21] we have presented a scheme for dealing with the EIE cross sections of atoms at low to high incident energies in a consistent way. We calculated the exact PWCS (σ…”

“…[14,18] Therefore, to calculate the EIE cross sections in the whole energy region efficiently, different methods should be used for different energy regions. [21] We have demonstrated for the e + He collision processes that the EIE cross sections of partial wave R-matrix method calculations can interface with the Born cross sections. [21] In the present work, we propose an effective method to conveniently calculate the EIE cross sections with enough accuracy in the whole energy region.…”

“…[21] We have demonstrated for the e + He collision processes that the EIE cross sections of partial wave R-matrix method calculations can interface with the Born cross sections. [21] In the present work, we propose an effective method to conveniently calculate the EIE cross sections with enough accuracy in the whole energy region. The e + He collision processes are used as an illustration example to show the validity and efficiency of our method.…”

“…[15][16][17] In the high incident energy region, the first Born approximation (FBA) is applicable and the EIE cross sections can be obtained from the generalized oscillator strengths (GOS). [18][19][20][21][22] Note that the quality of the target state wavefunctions is crucial for both partial wave expansion and GOS calculations. [14,18] Therefore, to calculate the EIE cross sections in the whole energy region efficiently, different methods should be used for different energy regions.…”

“…[25] Considering the computational efforts are very large to use the R-matrix method alone below the FBA calculation region, we extend the calculation scheme presented in Ref. [21] by using the distorted wave (DW) approximation [26,27] calculations in the intermediate energy region between the R-matrix calculation region and FBA calculation region. The application of the DW method makes the interface of the EIE cross sections between different energy regions more effective.…”