A Spectroscopic Determination of e/m

Rydberg constants for hydrogen and helium.—By an interferometer method the wave-lengths of the hydrogen lines at 6563A and 4861A were measured with reference to λ5015.6750 of He as standard. The values so obtained were, for the doublet at 6563A, 6562.7110±.0018 and 6562.8473±.0009; and for the doublet at 4861, 4861.2800±.0013 and 4861.3578±0022. Similarly the wave-lengths of the 4686 lines of ionized helium were found to be 4685.7030±.0012 and 4685.8030±.0026. From these values of the wave-lengths the Rydberg constant for hydrogen, R_H is calculated to be 109,677.759±.008, and the Rydberg constant for helium, R_He, to be 109, 722.403±.004.

Calculation of e/m.—The ratio of the mass of the electron to the mass of the hydrogen nucleus, m/m_H, is given by m/m_H=(R_He-R_H)(m_He-m)/R_H(m_He-m_H)=1.33648(R_He-R_H)/R_H. The value of e/m is given in terms of the Faraday constant as e/m=(m_H/m)(F/m_H). If the values of R_H and R_He calculated above be substituted in these expressions and if it be assumed that F=96470 abamp. per gr. mol. and m_H=1.0072, it is found that e/m has the value (1.7606±.0010)×10⁷ e.m.u. per gr.