Eagle Mounting Research Articles

An Eagle mounting for a three-metre concave grating

The paper describes the design of an Eagle mounting for a three-metre concave grating. By making use wherever possible of standard engineering parts, and by the adoption of kinematical principles in the design, an especially simple and economical form has been evolved.

On the astigmatism of the concave grating

For light of any given wave-length, the angle of incidence on a concave grating which gives minimum astigmatism has been calculated from the general expression for the astigmatism. To obtain the maximum efficiency with a Paschen mounting, the use of two fixed slits is suggested. For the lower orders an angle of incidence of about 13° is suitable. The astigmatism in the ultraviolet is then not harmful for most purposes. It is shown that the Rowland mounting is very inefficient as far as intensity losses by astigmatism are concerned, whereas the Eagle mounting represents very nearly the optimum condition. A method is suggested to make use of the astigmatism for intensity measurements.

Magnetic Resolution and Nuclear Moment of Rhenium

FOR some time the spectrum of rhenium has been the subject of investigation in the Amsterdam Laboratory “Physica”. With the Bulger E1 quartz spectrograph we have studied the spectrum of the arc and of the underwater spark. The hyperfine structure and the magnetic resolution have been investigated with the 20-ft. grating in an Eagle mounting.

The zeeman effect for the spectrum of tantalum

Among the elements whose arc spectrum has not as yet been analysed, one of some interest in Tantalum. Of atomic number 73, it occurs between Hafnium and Tungsten in the atomic table, and according to Bohr it is a homologue of Uranium X. As one of the most powerful methods we have available for investigating the structure of a spectrum is a study of the Zeeman effect shown by its constituent wave-lengths, we decided to use it with tantalum. The magnetically resolved components of over 50 of the more important wave-lengths of its arc spectrum were determined, and the results, together with an account of the investigation, are given in what follows. Apparatus . The light source used consisted of a modified form of vacuum arc and the arc chamber formed an integral part of an electro-magnet, which was of the Du Bois type. The grating, a 4-inch concave one with 15,000 lines per inch, had a radius of 3 meters and was used with an Eagle mounting. The photographs taken were those of second order spectra.