Fluorescence of the visible triplet lines of mercury (4047, 4358, 5461) was obtained by exciting a mixture of mercury vapor and a small amount of nitrogen by radiation from a quartz mercury arc. The fluorescence was observed at right angles to the exciting light beam and the polarization of each line, isolated by suitable filters, was measured by the method of crossed Wollaston prisms. Measurements in zero magnetic field (polarized excitation) gave 88.2 percent for 4047, -65.5 for 4358, and 14.55 for 5461, compared to theoretical values (broad line excitation) of 84.7, -67.0, and 8.7 percent, respectively. Measurements were then made of the polarization as a function of a magnetic field applied in the observation direction and the mean life of the
73S1 state calculated from the data. The mean life of this state as measured by 4047 and 4358 was 0.8\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec. at about 3.0 mm nitrogen pressure. The mean life as measured by the line 5461 was about 0.6\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec. The collision cross section for the
73S1 state against nitrogen was measured by measuring the polarization of 4358 at a field of 3 gauss and varying nitrogen pressures, giving the result ${{\ensuremath{\sigma}}_{q}}^{2}=1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$
cm2.
For the mercury 6s6p 1 P 1 and 6s6p 3 P 1 states excited by electron impact, the linear polarization of the light emitted in the transition to the ground state has been measured from threshold to intermediate energy for the decay photons of 254 and 185 nm wavelength, respectively. The results for both lines are in surprisingly good agreement with a calculation based on the Born-Ochkur approximation, neglecting spin-orbit terms for the continuum electron but allowing for electron exchange effects and intermediate coupling.