A New Determination of e/m from the Zeeman Effect

Values of $\frac{e}{m}$ have been determined from the Zeeman separations of the Cd line 6439 and the Zn line 6362. For these lines the $g$-factors can be accurately determined from the theory. A magnetic field of 7300 gauss was produced by an air core solenoid in which the variation of field strength over a length of 6 cm at the center was less than 0.1 percent. The field to current ratio, $K$, of this solenoid was determined in terms of the calculated ratios of three single layer standard solenoids. The field strength during an exposure was then given by the product of this constant and the current flowing. Evaporation of Zn and Cd in the short (6 cm) positive column of a helium discharge tube gave the desired lines. The Zeeman patterns were photographed with a Fabry-Perot interferometer. The result is $\frac{e}{m}=1.7579\mathrm{}\pm 0.0025\times {10}^7 \mathrm{e}.\mathrm{m}.\mathrm{u}.\mathrm{per}\mathrm{gram}.$