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Alpha particle energies watch

1. In my notes, it says "The energy of an alpha particle from radioactive decay is of a fixed value, but by using electrons it becomes possible to produce particles with much higher energies"

Why is the energy of an alpha particle fixed?

Thanks for any help

Rosie
2. (Original post by crana)
In my notes, it says "The energy of an alpha particle from radioactive decay is of a fixed value, but by using electrons it becomes possible to produce particles with much higher energies"

Why is the energy of an alpha particle fixed?

Thanks for any help

Rosie
Alpha particles are large and are ejected from the nucleus at near enough same velocities,so their kinetic energies will not differ that much either.
3. (Original post by IntegralAnomaly)
Alpha particles are large and are ejected from the nucleus at near enough same velocities,so their kinetic energies will not differ that much either.
But they have a + charge, so why can't you accelerate them in the same way as you can electrons?
4. You can accelerate protons to MeV energies using a Van de Graaff generator.
5. (Original post by crana)
Why is the energy of an alpha particle fixed?
the total momentum is zero initially. When it decays, the masses of the products, the daughter nucleus and the alpha particle, are fixed. So by conservation of momentum, m1v1+m2v2=0.
The energy released due to difference in masses is also fixed.
So 1/2(m1)(v1)^2 + 1/2(m2)(v2)^2 = constant
So it is fixed. The energy profile is used to contrast the situation of beta decay, where anti-electron neutrino is present and share the fixed amount of energy given to the beta particles and then anti-neutrino.

In alpha decay, as it is usually a heavy nucleus that decays to give alpha particles, speed of alpha particles is much higher than that of the nuclei. So nearly all the momentum goes to the particle.
6. nuclear enery levels are discrete, when the nucleus decays and emits a alpha particle, the total energy released is fixed. this energy is shared between the daughter nucleus and the alpha. after application of conservation of momentum, there is only one way to share the energy between the two particles, so alpha particles all have the same energy. as the alpha particle is much lighter, it has almost all of the energy/momentum. apologies, i dont have a mathematical proof.

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