Gamma $\gamma$ Radiation

The other form that radiation can take is gamma radiation. This is simply the emission of light. Recall that atoms can emit light when electrons drop from an energetic orbit (a larger orbit) to a less energetic orbit (a closer orbit). Each of these emission gives out a single photon of light. That light carries a specific amount of energy. These atomic emissions are relatively low energy compared to the very energetic nuclear emission of light. The protons and neutrons can be thought of as jostling about in the nucleus. They do not just sit there. They have a very high energy. When the nucleus settles into a more relaxed state, it gives up this energy in the form of high-energy light. The energy is related to the frequency and this light is in the range of x-rays and high energy gamma-rays. Since light is neither a proton nor a neutron, the atomic number and the mass number do not change. The element remains the same element; it is essentially just calmer. The notation for this is

$$\mbox{${}_{56}^{}$ {Ba${}^\ast$ }${}_{}^{137}$ } \rightarrow \mbox{${}_{56}^{}$ {Ba}${}_{}^{137}$ } + \gamma$$

The asterisk indicates that the barium started out in an excited state and then decayed to the not-excited state by giving up a photon $(\gamma)$.