Small Moment Of Inertia Research Articles

A new electrometer

The construction, mode of use and properties of a small static electrometer are described. The moving element has the form of a multi-needle, and is characterized by extreme lightness and very small moment of inertia.

Interpretation of the spectra of CaF and SrF

The structure of the band spectra of the diatomic alkaline earth fluorides has been considered in the light of the quantum theory by Mecke, Jevons, Johnson, and Jenkins. Because of the closeness of the rotational structure it has proved impossible to obtain sufficient resolution for the application of the combination principle to the individual band lines except for BeF, which molecule has the smallest moment of inertia (Jenkins, loc . cit .). With the heavier molecules, assignments of vibrational quantum numbers were made from the positions and intensities of the band heads, and designations of the electronic terms were given, based on the evident similarity of certain band systems in this group of molecules. The 2 Π→ 2 Σ system, which lies in the ultra-violet for BeF and MgF, and in the visible for CaF, SrF and BaF, was shown in the case of BeF to possess the expected rotational structure. The system designated 2 Σ→ 2 Σ by Johnson is known only in CaF, SrF and BaF, and has a slightly higher frequency than 2 Π→ 2 Σ. In the course of a search for isotope effects in the spectra of CaF and SrF have obtained plates with the 21-foot concave grating showing the two systems mentioned above in both emission and absorption. For the absorption the method of Walters and Barratt was used. Although the study of these plates gave evidence of isotopes only in the case of SrF, certain observations on the modifications in structure between emission and absorption are important for the interpretation of the rotational structure of the bands of both molecules, a question which apparently can only be cleared up by indirect evidence of this kind.

A Possible Origin of the Nebular Lines

THE hypothesis that the lines of unknown origin in the spectra of nebulae are due to the atom of some hitherto undiscovered element (“ nebulium ”) is not the only one that may be advanced. The recently developed quantum theory of band spectra makes it at least possible that these lines could have their origin in a molecule with small moment of inertia composed of atoms of those elements which are known to exist in nebulae. It is proposed in this letter to show that the existing astronomical evidence is not in contradiction to this alternative hypothesis, and also to indulge in some speculation as to the nature of such a molecule.

On a Coil-Galvanometer of Rapid Indication

The galvanometer is designed to secure rapid indication and steadiness of reading without unduly sacrificing the sensibility. The coil is long and narrow, and therefore of small moment of inertia: the mirror is supported by the wires forming the coil, between which it is slipped, and the coil is supported between an upper and a lower vertical wire, as distinct from strips, made of silicium bronze and put in tension.