This function will be evaluated between N=0 to N=nmax-1 at integer and half-integer values.
The cluster size distribution starts at a size of 0, not 1. The reason for this is that most interactions between charged particles and gas molecules result in excitation, rather than ionisation. In the absence of Penning transfers, these interactions will not lead to ionisation electrons. In case you enter a cluster spacing which only takes ionisations, and not excitations, into account, then you have to set the probability at N=0 to 0. This can most easily be done using the Mixed format.
Samples are taken at N, N+0.5 and N+1 and the probability that is assigned for a cluster size of N is the Simpson integral over these 3 points. The rationale for this approach is that it is anticipated that an energy transfer probability divided by work will be entered, so that the derived cluster size is the ratio truncated to the next lower integer, rather than the ratio rounded to the nearest integer.
You don't have to worry about the normalisation.
[There is no default function.]
Values between 1 and MXPAIR are permitted.
If set to 1, then only clusters of size 0 will ge generated. I.e. not a single ionisation electron will be produced.
[Default is MXPAIR, set to 2000 at the time of writing.]
Formatted on 21/01/18 at 16:55.