Question 14: What is optical pumping?
Optical pumping is the process in which atoms of a substance in the ground state E1are raised to the excited state E3.
Consider a substance having the metastable state. The atoms of this substance are raised to the excited state E3 by optical pumping, i-e, providing energy from the outside surroundings. Now the atom in the excited state E3 does not decay back to the ground state but to the metastable state E2. Normally, the atom remains in the excited state for a time interval of 10-8 seconds. But in the case of meta stable state it remains there for a longer time of 10-3 seconds. Therefore, the population of electrons in the meta stable state increases. After some time the population inversion is achieved. This process is called optical pumping.