New Experimental Determination of Effective Cross-Sections for the Quenching of Mercury Resonance Radiation

Abstract

Theory of the quenching of resonance radiation. The problem of the quenching of resonance radiation by foreign gases is treated on the basis of Milne's theory of diffusion of radiation extended to take account of (1) a collimated incident beam, (2) a finite emission line, (3) a finite absorption line, (4) impacts of the second kind, and a curve is obtained from which one can find the number of impacts of the second kind corresponding to any experimentally observed value of the quenching. The effect of metastable atoms is discussed and a theory of their behavior outlined.Measurement of the quenching of mercury resonance radiation. The scattered radiation emerging from an absorption cell containing mercury vapor in the presence of a foreign gas was measured as a function of the gas pressure with apparatus designed to agree closely with the requirements of the theory. From the theoretical curve the number of impacts of the second kind was obtained, and from this the effective cross-section for quenching was calculated for the following gases: ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, N${\mathrm{H}}_{3}$, C${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$O, ${\mathrm{N}}_{2}$, C${\mathrm{H}}_{4}$, ${\mathrm{C}}_{2}$${\mathrm{H}}_{6}$, ${\mathrm{C}}_{3}$${\mathrm{H}}_{8}$, ${\mathrm{C}}_{4}$${\mathrm{H}}_{10}$, He and A. The values of the effective cross-section for quenching are tabulated along with those for depolarization of resonance radiation and for collision broadening. The quenching cross-sections of CO, N${\mathrm{H}}_{3}$, C${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$O, ${\mathrm{N}}_{2}$, C${\mathrm{H}}_{4}$, ${\mathrm{C}}_{2}$${\mathrm{H}}_{6}$ and ${\mathrm{C}}_{4}$${\mathrm{H}}_{10}$ are shown to be connected with the difference between the energy of the transition $2^{3}P_{1}\ensuremath{-}2^{3}P_{0}$ of Hg and the vibrational energy of the molecules, in qualitative agreement with the theory of Kallmann and London.