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In this paper (the first of a series), we present a general analysis of the parity violating phenomena induced by neutral currents in Atomic Physics. We first give expressions for the short range parity violating electron-nucleus and electron-electron potentials predicted by the theoretical schemes of weak interactions featuring neutral currents. We turn next to a detailed computation of the matrix element, between one-particle s and p states, of the electron-nucleus parity violating potential. Using a non-trivial extension of a method used by Foldy to put on a more rigorous basis a formula of Fermi and Segre giving the wave function of an s valence electron at the nucleus, we arrive at a remarkably simple expression, in terms of the binding energies, with a small correcting term involving the interpolated quantum defect and the potential of the electronic cloud at the origin. Arguments are given which lead us to believe that the accuracy of our formula is comparable to that of the Fermi-Segre formula, i. e. a few per cent when Z >> 1. Besides its simplicity, a remarkable feature of our result is a Z3 dependence, which obviously favours heavy atoms. We give a brief analysis of the manifestation of parity mixing in atomic radiative transitions, with a particular emphasis on the implications of time reversal invariance, which is preserved by the interactions discussed in this paper. In order to improve the existing limits, we suggest looking for parity violating effects in twice forbidden magnetic dipole transitions induced by a tunable laser beam in heavy atoms. In a typical case, like the 6 S1/2 → 7 S1/2 transition in atomic Cesium, a circular dichroism of the order of 10-4 is predicted. Finally we discuss the apparently more remote possibilities offered by the muonic atoms.

It has been conclusively proved in the last two years that there is a significant effect of the solvent on the measured value of dipole moment of a solute. It has also been shown that the effect is mainly determined by the dielectric constant of the medium, suggesting a relatively simple physical cause, but the precise law of relationship is still disputed. A list of the formulae which had been proposed at the time of the Faraday Society's discussion is collated by Goss. These all have the status of empirical formulae, since that of Raman and Krishnan contains two difficult accessible constants. The theory formula of Weigle is omitted from this list. It receives some discussion in the next section of this paper. These formulae agree in disregarding the properties of the solute, excepting its dipole moment. The solvent effect is considered to be proportionately the same for all polar substances. Müller makes an exception in suggesting a modified law for certain substances, mainly ketones. The hydrogen halides, with positive solvent effects, are considered entirely anomalous, and their increase of moment is attributed to an intramolecular change towards more ionic linkage.

The fact that a magnetic dipole μ moving with velocity βc has an electric dipole moment p = β×μ/c has made periodic appearance in the literature but the importance of this fact and its general utility have not been given sufficient expression. It is the purpose of this paper to show how to derive the equation p=β×/c and then to use it for a simple description of the atomic spin-orbit interaction.

The method of solving the Thomas-Fermi equation, developed in a previous paper 1), is applied to the H2O-molecule. The electronic density is calculated. A proof is given that the Thomas-Fermi method, or generally any method, which treats the electrons as a continuous cloud of electricity obeying the Poisson equation, gives a zero value for the electric dipole moment of any molecule. © 1955 Stiching Physica, Amsterdam, Nederland.

Of the methods which have been devised for the measurement of angles between covalencies, the one based on measurements of electric dipole moments is among the most valuable. Descriptions of considerable experimental work on the subject have been published by several authors, but the discussions of the basis of the method, its further possible applications, the possible errors and their probable importance, are not only scattered, but incomplete. It therefore appeared desirable that a more complete, general treatment of these matters should be given, and the present communication is an attempt to do this.

The present paper considers the VLF radiation characteristics from a thin dipole antenna in a warm magnetoplasma. Formal solutions are derived for the portions of the dipole radiation resistance due to the thermal modes (Rt) and the whistler mode (Rw). In this derivation the ions are assumed to be cold, and the effects of finite electron temperatures are included by means of a scalar pressure term. Two particular orientations of the dipole are considered (parallel and perpendicular to the static magnetic field line). A detailed analysis is made for frequencies in the range between the electron gyrofrequency (fHe) and the lower-hybrid-resonance frequency (fLHR). Several numerical plots of Rt ∥, and Rw∥, are presented for typical VLF magnetospheric plasma parameters. They show that for frequencies ( f) not close to fLHR, Rt∥, is generally < 2 x 10-1 Rw∥, whereas as f → fLHR, R t , ≃ 10-1 Rw and R t∥ ≃ Rw∥. Using these numerical values of Rt∥, and Rw∥,, the dipole whistler mode radiation efficiences ηw have been estimated for a number of specific cases. In most cases ηw ≳ 70 %, but falls as low as ∼ 38 % at f ≃ f≳ LHR.

In this paper we propose that chemicals such as acetylcholine are electric dipoles which when oriented and arranged in a large array could produce an electric field strong enough to drive positive ions over the junction barrier of the post-synaptic membrane and thus initiate excitation or produce depolarization. This theory is able to explain a great number of facts such as cleft size, synaptic delay, nonregeneration, subthreshold integration, facilitation with repetition, and the calcium and magnesium effects. It also shows why and how acetylcholine could act as excitatory or inhibitory transmitters under different circumstances. Our conclusion is that the nature of synaptic transmission is essentially electrical, be it mediated by electrical or chemical transmitters.

Numerous types of resonance methods for the measurement of dielectric constants have been described by different investigators. That detailed in the present communication has no claim to originality, but it is a simple, whilst at the same time reliable, form, which has proved to be very useful for the measurement of the dielectric constants of dilute solutions for the purpose of dipole moment determination. A fairly powerful oscillator is used, enabling the valveless resonance circuit to be some distance removed from it, whilst still receiving ample “pick-up” for the measurements. Resonance in the pick-up circuit is detected by means of a low-resistance thermo-junction, introduced directly into the circuit. The resistance thus introduced does not damp the oscillation unduly. The very small conductivity of the solvent liquids employed does not produce any appreciable error owing to the current resonance not occurring at the same tuning capacity as the voltage resonance.

The infra-red absorption of ionic crystals differs in important details from the predictions of the theory based on first approximations. It is known that this discrepancy may be due to two effects which are neglected in such a theory, namely, to the anharmonic terms in the potential energy and to those terms in the dipole moment which are of higher order than the first in the displacement co-ordinates. These higher-order terms in the dipole moment arise from the deformation of the electron shells. The present paper develops in a systematic way the influence of these higher-order effects on the static dielectric constant. Because of the dispersion relations, the terms occurring in the static dielectric constant must also appear in the infra-red absorption spectrum . It is found that the third- and the fourth-order potential, the second- and the third-order dipole moment, and cross-terms between the second-order moment and the third-order potential, all con­tribute terms in the same order to the static dielectric constant. It is also found that the third-order potential contains important contributions from the long-range dipolar inter­action. These dipolar contributions are proportional to the product of the first- and second-order dipole moments, and it follows that in ionic crystals a large second-order moment automatically results in a large third-order potential. It is suggested that these dipolar contributions to the third-order potential may be responsible for the fact that in the infra-red spectra of different ionic crystals not only the intensity of the side band but also the width of the main band varies in the same way as the deformability of the electron shells.

The purpose of this paper is to give the complete classical theory of a spinning particle moving in a Maxwell field. The particle is assumed to be a point, and its interaction with the field is described by a point charge g 1 and a point dipole g 2 . The Maxwell equations are assumed to hold right up to the point representing the particle. Exact equations are then derived for the motion of the particle in a given external field which are strictly consistent with the conservation of energy, momentum and angular momentum, and hence contain the effects of radiation reaction on the motion of the particle. It is shown that in the presence of a point dipole the energy tensor of the field can and must be redefined so as to make the total energy finite. The mass, the angular momentum of the spin, and the moment of inertia perpendicular to the spin axis appear in the equations as arbitrary mechanical constants. Reasons are given for believing that for an elementary particle the last constant is zero, in agreement with relativistic quantum theory. In the general theory there is no relation between the electric and magnetic dipole moments of the particle and the state of its translational motion. A procedure is given for deriving from the general equations specialized equations consistent with the condition that the dipole is always a purely magnetic or electric one in the system in which the particle is instantaneously at rest. The radiation reaction terms are very much simpler in the former of these specialized cases than in the general case. The effect of radiation reaction is to make the scattering of light by a rotating dipole decrease inversely as the square of the frequency for high frequencies, just as for scattering by a point charge.

The idea that a molecule need not necessarily have a single Kossel Lewis-Langmuir electronic structure, but may be a hybrid of several such, is not new in chemistry, Recently, however, it has been given a much more definite meaning, and has been made amenable to quantititative treatment by the application of wave mechanics to the problem; moreover, it is now realised how extensive the phenomenon is, owing largely to the work of Pauling and his collaborators on energies and internuclear distances. It is the purpose of this paper to show that it is possible, from electric dipole moment data, to decide independently whether or not there is resonance in a molecule, and also to obtain a rough idea of the nature of the more important parent structures and of their relative importance.