Question 14: What is optical pumping?

ANSWER

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.