Electron Impact Cross Section Calculations Using The Average Approximation
This is your gateway to the calculation of electron impact excitation cross sections for atomic ions using the average approximation of Peek and Mann. This code was brought to the Atomic and Molecular Data Unit of the International Atomic Energy Agency by J.M. Peek during his visit to the Unit as a consultant. The well known Hartree-Fock code of R.D. Cowan, developed at Group T-4 of the Los Alamos National Laboratory, is used for the atomic structure calculations.
The expected accuracy of the average approximation compared to a distorted wave calculation varies depending on the charge state and impact electron energy. In general, for lower charge states and lower energies the accuracy is poor and can be as much as a factor of two near threshold for a near neutral case (neutral atoms are not permitted). For energies above two or three times the threshhold and for more than once or twice ionized, the accuracy typically approaches 10% for optically allowed transitions and slightly worse for non-allowed transitions. Resonance processes are not included in this calculation.
On the following pages you will be able to define the ionization stage of an element and pick the initial and final configurations. You will be led through a series of web pages ending with a display of results in the form of cross sections or collision strengths.
WARNING - In order to successfuly navigate you must use the radio buttons to go to and from different pages. Using your browser buttons may cause incorrect information to be passed to a new page. Please use the exit button to end the calculations.
Click here to proceed with the cross section calculation
Click here to go to IAEA Atomic and Molecular Data Unit