Input Parameters

The physical input parameters in the BASIC MODE are

(a) The projectile nuclear-charge number Z_p (the atomic number, with Z_p > 0). The Zp button may be used to select the type of projectile from a periodic table. The projectile charge state can be now  directly selected by pressing the button "Charge State".

(b) The projectile energy per nucleon (E_p/M_p in keV/u). Here 25 keV/u corresponds to a velocity of 1 atomic unit (1 a.u.) or 2.2E6 m/s. (α*c). In the current version of CasP, E_p/M_p should not exceed a few 200 MeV/u, because of neglected higher order relativistic effects.

(c) There are two ways to define the target system: either by selecting the target nuclear charge (Z_t) or by typing the chemical formula for the target.

• The target nuclear-charge number Z_t (the atomic number) for an element may be entered directly or the Zt button may be used to select the type of target from a periodic table of the elements.
  
  
• In the case of compounds, the COMPOUND check-box has to be selected and a chemical formula for the target has to be typed directly. The chemical formula will be then interpreted in order to recognize the chemical elements (this is case-sensitive) and their quantities. The typed formula consists only of numbers, small and capital letters (no subscripts). For defining, e.g., water you may use H2O or OH2 or HOH. The typed chemical formula will determine the target shell structure and the mean projectile charge-state is estimated for the given target compound. The stopping cross-section per molecule is calculated from the target shell structure using Bragg’s additivity rule (linear superposition of independent atomic cross sections). The averaged mean projectile charge-state is determined from the mean charge-state corresponding to each target atom, weighted with the atomic fraction as well as with the charge-changing cross section (assumed to be proportional to Z_t). Attention: each compound is initially assumed to be a solid (or a liquid). In order to define a molecular gas target one has to select the GAS TARGET check box (see EXPERT OPTIONS, FURTHER TARGET DATA) after defining the chemical formula.

(d) The mean target-ionization potential I_Bethe in eV, as it appears also in the Bethe formula. An estimate for this value is derived from Z_t and used as a default (this value is also used if the COMPOUND check-box is selected).

Furthermore, the name of the output file for the Q_e(b) results of all shells may be chosen within this mode.

If the option CREATE DEFAULT FILE NAME is selected, a file name is automatically created, dependent on the type of model (”u” for UCA and ”p” for PCA), on the actual screening function (”n” for NONE, and ”b”, ”s”, ”g”, ”m” for the others), and on the projectile energy. This option shall simplify the calculation of energy dependencies for Q_e(b). You may, however, overwrite this name after all physical input parameters have been selected.