# How do alpha and beta particles ionise surrounding particles?

I've been wondering about this question for a while. If you have alpha and beta particles released from a radioactive core, how do they ionise surrounding particles?

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When alpha particles (helium nuclei) or beta particles (electrons) are released in a radioactive decay they carry significant kinetic energy. As they go through the surrounding material they bump here and there occasionally kicking off some electrons from the surrounding atoms which are then ionised, until they finally stop.

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So, the only transfer of energy that occurs is kinetic energy, or is it also because negative charges repel each other? – amy Feb 10 '11 at 10:16
@ Jaydon: The energy transferred to the electron comes from the kinetic energy of the ionising particle. The fact that the two can interact come from the fact that they both interact electromagnetically, regardless of the sign of their charge. Notice that in radioactive decay you can also have gamma particles (high energy photons) which aren't charged, but also interact electromagnetically and thus can ionise the medium. – inovaovao Feb 10 '11 at 10:23
Will there be an additional force on the electron due to their electromagnetic interactions? (between, say, the beta particle and shell electron) – amy Feb 10 '11 at 10:26
whether the beta particles are electrons or positrons depends on the kind of beta decay, and positrons can then simply annihilate other electrons (one electron per positron) – Tobias Kienzler Feb 10 '11 at 10:49

Alpha particles are the nuclei of He, i.e. lacking the two electrons they carry a charge of $+2e$, while beta particles are either electrons or positrons and thus carrying a charge of $\mp 1e$. Positrons meeting other atoms' electrons annihilate thus leaving a positive ionization. The other particles may just carry enough momentum to transfer the energy required for the ionization of shell electrons.

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## protected by Qmechanic♦Jun 4 '14 at 15:30

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