Alfred Kastler — French Physicist 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.