none excited, four at ground level :INCOMING PHOTON

LOW TEMPERATURE EQUILIBRIUM STATE

The system starts off at very low temperatures which implies that almost all of the quantum systems are in the lowest state of minimum potential energy.

What is most likely to occur when the photon reaches the system ?

  1. Photon absorption (transition from lower to upper quantum state)
  2. Stimulated emission by a photon (transition from upper to lower quantum state)
HINT:
Absorption dominates over stimulated emission when the lower level has a larger population.