If a nucleus has excited states above the ground state at energies 300 keV, 200 keV, and 80 keV, what gamma rays (in keV) may be expected from a collection of these excited nuclei? The ground-state energy is at 0. Choose the most complete set.

Question

Quizplus · Accepted Answer

When an excited nucleus returns to its ground state, it emits a gamma ray with energy equal to the difference between the energy of the excited state and the ground state. Therefore, the possible gamma ray energies are:

- From the 300 keV state: 300 - 0 = 300 keV
- From the 200 keV state: 200 - 0 = 200 keV
- From the 80 keV state: 80 - 0 = 80 keV

In addition, there can be gamma rays emitted from transitions between the excited states themselves:

- From the 300 keV state to the 220 keV state: 300 - 220 = 80 keV
- From the 220 keV state to the 200 keV state: 220 - 200 = 20 keV
- From the 200 keV state to the 120 keV state: 200 - 120 = 80 keV
- From the 120 keV state to the 100 keV state: 120 - 100 = 20 keV

Therefore, the complete set of possible gamma ray energies is {300, 220, 200, 120, 100, 80}. Choice E is the only one that includes all of these energies.

If a Nucleus Has Excited States Above the Ground State