Mod-01 Lec-29 Gamma decay

So, after alpha decay and beta decay, the next topic will be gamma decay all this 3 you have done during your school days college days. In alpha and beta decay nucleus changes whereas, in gamma decay if the same nucleus which deexcites from some excited state to either ground state or a lower excited state. So, it is the nucleus is same and you have

the energy levels of the nucleus depending on. What nucleus it is? So, if the nucleus is somehow placed in 1 of this excited state it just deexcites and emits photon and that is called gamma ray and this whole process is gamma decay. Now, placing nucleus in excited state normally that is through beta decay or sometimes alpha decay when a nucleus decays

through beta process or alpha process quite often the brothel nucleus is created in the excited state to start with and from there it decays to lower states emitting these gamma photons. So, I give u some examples, 1 is see this is 137 cesium z is 55 this decays to barium,

excited state barium. This is barium 137 and this is 56. So, from 55 it becomes 56 it is beta decay a neutron is converted into proton. So, 95 percent of times when this decay the cesium decays 95 percent of the time it decays to this excited state. And 5 percent of times it decays to the ground. This excited state has a half life of 2.55 seconds and energy

here energy difference here the first excited state here is at 662 k e V. So, through this beta decay when it comes the cesium 55, 137. When this nucleus is converted into barium 137, 56 here that is in excited state and when it decays to ground state with this half life of 2.55 minutes your gamma photon is emitted.