The Effect of Hyperfine Structure on the Polarization of Resonance Radiation in a Magnetic Field.

 Bertrand John Miller

Lewis Larrick

Allan C. G. Mitchell

Breit has derived formulae giving the polarization $P(H)$ and the angle of maximum polarization $\ensuremath{\theta}$ of a resonance line showing hyperfine structure, as a function of a weak magnetic field applied in the direction of observation of the resonance radiation. The formulae give a means of estimating the effect of hyperfine structure on the calculation of the mean life $\ensuremath{\tau}$ of an excited atom from experiments on the magnetic depolarization and rotation of the plane of polarization of resonance radiation. The calculation has been carried through for the case of the resonance line of $\mathrm{Cd}(\ensuremath{\lambda}3261)$ and that of $\mathrm{Hg}(\ensuremath{\lambda}2537)$, and it is found that the differences between the value of $\ensuremath{\tau}$ calculated from hyperfine structure data and that calculated from $tan2\ensuremath{\theta}$ by the usual non-hyperfine structure method lie well within the experimental error. $\frac{P(H)}{{P}_{0}}$ is found to be practically the same whether hyperfine structure is taken into account or neglected. This is due to the fact that the greatest contribution of the polarization in these cases comes from the isotopes having no nuclear spin and the $g$-value for the upper state of these isotopes is larger than any other upper hyperfine structure state involved. The mean lives of the $7^{3}S_{1}$ state of mercury have been recalculated from Richter's data on the polarization of stepwise radiation. The values of $\ensuremath{\tau}$ obtained by this method of calculation are 7.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ for $\ensuremath{\lambda}4047$, 1.69\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}4358$ and 1.53\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}5461$. A discussion of Richter's results is given.

Allan C. G. Mitchell

The general theory of the calculation of the polarization of resonance radiation is discussed for the case when hyperfine structure has to be considered. The polarization of mercury resonance radiation is computed for various orientations of electric vector and magnetic field, use being made of the hyperfine structure data of Sch\"uler and his collaborators. The polarization of the stepwise radiation of mercury is also calculated and the results compared with the experiments of Richter. Fair agreement between theory and experiment is found. von Keussler's method of calculating the polarization is discussed and it is shown that his method leads to incorrect results.

A. A. Kiselev, A. V. Lyaptsev

A. Ellett, Walter A. MacNair

The incomplete polarization of $\ensuremath{\lambda}2537\mathrm{A}$ of mercury in resonance radiation is due to the peculiar behavior of the outer two hyperfine structure lines. The three remaining hyperfine structure lines behave in accordance with the predictions of the theory of the anomalous Zeeman effect for a ${1}^{1}$${\mathrm{S}}_{0}$-${2}^{3}$${\mathrm{P}}_{1}$ line. Von Keussler's observation of complete polarization in 7900 gausses is explained, in part at least, by the observed shift of the -25.6 hyperfine structure line, and complete polarization is obtained with a field only 2000 gausses using a resonance radiation source.