Hello If a heavy ion beam deposits a certain energy E in a volume V, how many ion-pairs will it produce in matter? I think that the number of ion-pairs will be the energy divided by the (average) energy of ionization. A friend told me that a part of the deposited energy will cause also atomic excitations without ionizations, but we don’t know the fraction of energy for each process. I suppose that the fraction of excitations will be negligible compared to ionizations, but I’m not sure of that. Thank for your time (with a reference to a book will be enough). Greetings!