Depolarization of Resonance Radiation

Abstract

Depolarization and quenching of mercury resonance radiation are phenomena of quite different type. Depolarization is produced by two effects. With gases which quench by effecting the transition $^{3}P_{1}\ensuremath{\rightarrow}^{3}P_{0}$ upon collision with Hg\ensuremath{'} atoms, there exists a pronounced reverse transition $^{3}P_{0}\ensuremath{\rightarrow}^{3}P_{1}$ produced by collision with high speed molecules. Atoms which radiate without any collision emit polarized light under the conditions of the experiment. Those which become $^{3}P_{1}$ atoms after having existed as $^{3}P_{0}$ atoms have experienced a large number of collisions and have lost their orientation relative to the incident electric vector; accordingly they emit radiation polarized in random directions. The second depolarizing influence arises in collisions at distances exceeding the ordinary kinetic theory collision such as is described above, at which the distance is too great for a collision of the first or second type, but still small enough for the field of the gas atom to exert a perturbing influence on the orientation of the Hg\ensuremath{'} atom. Depolarization by ${\mathrm{H}}_{2}$ is an excellent example of the second influence while the first effect is sufficient to interpret the experimental data with the rare gases, the atomic fields of which decrease with a high power of the radial distance.