In order to access this option you should select the EXPERT OPTIONS sheet (close to the upper left corner of the main program window).
Dependent on the target atomic number, on the projectile velocity, and on the required numerical accuracy an optimized quadratic impact-parameter grid is selected, if this option is chosen.
If this option is not checked, the minimum impact parameter bmin, the maximum impact parameter bmax (both in units of Å), and the number of grid points may be selected directly. The impact parameter range should always stay within 1E-5 ... 100 Å, to avoid numerical problems inside CasP. The selected number of grid points (n) should be >> 1 (and < 1000), to allow for the internal impact-parameter integration. The first b value is exactly bmin, the last impact-parameter value is bmax, and n-1 grid points are distributed in between (quadratic grid). The Q_e(b) results for all impact parameters and for all shells are stored in an output file.