The Deflection of Molecular Rays in an Electric Field: The Electric Moment of Hydrogen Chloride

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Abstract
A comparison of the method for determining electric moments of molecules by deflection of molecular beams by inhomogeneous electric fields with the dielectric constant method shows that the molecular beam method has certain advantages. This method determines the electric moment of gases directly and is able to detect the effect of higher rotational states of non‐gyroscopic molecules. Moreover, a deviation of the axis of the dipole moment from that of the axis of rotation by other than 90° should be detected. The additional energy due to an electric field is proportional to the square of the field intensity and is a function of the quantum numbers m and j, if the electric moment is perpendicular to the axis of rotation. Otherwise there will be a linear dependence on the intensity of the electric field. An experimental method of the Rabi type for studying the HCl molecule is described. The patterns produced by the undeflected and deflected molecules are given and from these patterns the electric moment of the HCl molecule is found to be approximately 1.95×10—18 e.s.u.