I have been told, that neutron radiation, rather than electron or proton radiation, is used to produce defects in solids. And the reason is that electron has a small mass comparing to the nucleus of an exerted atom, thus can not really displace it, and concerning protons, that most of their energy goes to the electron excitation. 1. Why neutrons don't excite electrons, and why most of protons energy goes to electron excitation rather than atom displacement? 2. Do I understand correctly, that excitation of electron due to the massive particle is a result of massive collision of it with some incident particle, thus transferring kinetic energy from this particle to the electron internal energy? Thank you.