PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 3 JUNE 15. 1917 Number 6 
THE STARK EFFECT IN HELIUM AND NEON 
By Harry Nyquist 
SLOANE LABORATORY, YALE UNIVERSITY 
Communicated by H. A. Bumstead, April 20, 1917 
Stark^and Koch^ have studied the effect of an electric field on the spec- 
tral lines of helium by a method which was designed by Stark. Bru- 
netti^ and Evans and Croxson^ nave studied the effect in the same sub- 
stance by a method devised by Lo Surdo.^ The results obtained by the 
two methods agree in the main, but hitherto the method of Stark has 
proved capable of greater refinement than that of Lo Surdo. 
In the present investigation a method has been employed which is 
essentially a modification of Lo Surdo 's but avoids the greatest disad- 
vantages of that method. Lo Surdo's discharge tube is about 3 mm. in 
diameter and has a cylindrical cathode nearly filling it. The positive 
rays in the space before the cathode are in a strong field and are suit- 
able for the study of the effect. The disadvantages of the method are, 
first, that the walls of the tube are quickly covered with a metallic film 
due to sputtering and, second, the tube breaks easily on account of the 
heating. In the present apparatus these difficulties are overcome by 
having within the discharge tube proper an inner tube made of aluminum 
through which the discharge takes place, and which has a slit through 
which the light passes. Opposite this slit there is a side tube having a 
window at its end. The aluminum is not seriously affected by the 
heat and the trouble from sputtering is eliminated. 
The optical apparatus consists of a six prism spectrograph and a 
double image prism so arranged that photographs of the parallel and 
perpendicular components of the lines can be obtained simultaneously. 
The source of current is a 13,200 volt transformer, the current from 
which is rectified by two kenotrons and a suitable arrangement of con- 
densers and inductances. 
399 
PEOCEEDINGS OP NAT. ACAD. OF SCI., VOL. 3, NO. 6 
