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Alfred Kastler —
born on May 03, 1902,
died on January 07, 1984
Alfred Kastler was a French physicist, and Nobel Prize laureate... (wikipedia)
We should note that this latter type of shift was successfully amplified to a considerable extent by Russian physicists using the intense light of a ruby laser whose wavelength is close to that of a transition of the potassium atom.
I must confess that, at that time, I had absolutely no knowledge of the slowness of the relaxation processes in the ground state, processes which take place in collisions with the wall or with the molecules of a foreign gas.