Coupled-channels Optical Calculation Of Electron-carbon Scattering

It is well known that electron-atomic carbon scatteringproblem is a fundamental problem in theoretical atomicphysics. Atomic carbon is an important element of the worldand serves as a diagnostic tool for physical conditions. Theinvestigation of the electron-atom collision processes plays anessential role in study, the interaction of electron with generalmatter can afford some information of motion and correlationwhich the interaction of general matter with general matter cannot afford. In addition to its fundament nature, the study ofelectron-atom collision is also motivated by its widely used inastrophysics, atmospheric science, x-ray lasers, magneticfusion, radiation physics, and semiconductor fabrication. Forexample, carbon compose materials are also used in differentlaboratory plasma devices such as the tokamak at the JointEuropean Torus. Carbon is such an important target. However,the available cross-section data of electron impact on carbonare rather scarce.The momentum space coupled channels optical (CCO)method has broad success for a number of atoms whosestructure can be described by one or two active electrons, forexample hydrogen, alkali-metal elements, helium, andmagnesium et al. It uses the Feshbach operator P and Q tosolve a set of coupled integral equations in momentum space.And the continuum states of target are included in the coupledintegral equation with an ab intito complex optical potential.We used the momentum-space coupled-channels opticalmethod(CCO) to investigate the open-shell carbon atom. Thedirect ionization cross sections of 2p outer shell,1s22s22p2--1s22s22p3s , 1s22s22p2--1s22s22p3p ,1s22s22p2--1s22s22p3d excitation cross sections and totalcross sections have been presented at the energies below 200eV.The resonance structures in the low-energy in the1s22s22p2--1s22s22p3s and 1s22s22p2--1s22s22p3pexcitation cross sections have been reported in this paper. Andpresent CCO calculations have been compared with othertheoretical and experimental measurements.In this paper, we used the momentum-space coupled-channelsoptical method to study the electron impact on the open-shellcarbon atom. The large discrepancies in magnitude exist incomparing with other theoretical calculation results, which areattributed to the different treatment of the continuum since thelarge polarization effect come from transition to continuum.In summery, the improvement on the method ofmomentum-space optical potential is successful. The presentresults show that the CCO method is capable to calculateelectron scattering from open-shell atoms, despite we use aquite simple model to represent the wave functions of thetarget. Furthermore, there is an intense need for experimentaland possibly additional theoretical studies in order to establishreliable electron scattering data for atomic carbon.