A method combining the relativistic multichannel theory with the multichannel quantum defect theory is presented to calculate electron impact excitation. The collision strengths and rate coefficients of U⁹¹⁺ ion are computed with this method. Comparison with the results of R-matrix calculation shows that a) there exists another group of resonances near the excitation threshold; b)with the present method resonance structure can be fully resolved; c)the effective collison strength for 1s-2s transition at low temperiture is almost 20% enhanced by the resonances near the threshold.

In astrophysics, plasma, quantum chemistry and advanced technique, an increasing demand for collision data is evident. Among those data,cross section of electron impact excitation is important and fundamental data. In this paper, we present the electron impact excitation cross section for some ions at high-energy incident electron. In our calculation, the LS coupling antisymmetric single configuration wavefuction of the target has been used. The plane wave BORN approximation has been used in treating the collision problem. Angular part of the transition matrix element of complex atom is treated carefully. We have computed single electron radial wavefunction of atom by means of HARTREE-FOCK-SLATER self consis-tent field method. We call our computer program as PBA(9). By thiscomputer progrom, we can compute excitation cross sections, collision strengths, generalized oscillator strengths and optical dipole oscillator strengths. In fact, we have computed widely from H-like to Ne-like iso-electronic sequences. It is made to compare our results with the other ones available. It shows that our results are satisfying for high energy electron. For example, the values of the excitation cross section for C and O fall into the accurate region of recommend data given by Japan's center NAGOYA of atamic data. We conclude that the method used in this paper is reliable and the results are correct. It can provide us with electron-impact excitation useful informantion of light atoms (ions)by high energy electron.