SPECTROPHOTOMETRIC STUDY OF KATHODOLUMINESCENCE. 



I 4 I 



SIDOT BLENDE. 



The specimens tested were pieces of the same screen that had been used 

 in the work on Sidot blende described in Chapters IV and V. 1 



Our first measurements of the kathodo-luminescence of this substance 

 were made in connection with this earlier work, and although the conditions 

 were not so definite as in the case of the more recent investigation, the 

 result of one exploration of the spectrum, shown in Fig. 147, will be of 

 interest for purposes of comparison. Kathode rays were developed in 

 these experiments by connecting the tube used with the secondary of an 



30 V M 



50 52 54 56 58 60 62 fa 



Fig. 146. Willemite. 



The curves to the left are voltage-intensity curves for different wave-lengths. Curves /, //, and /// show the 

 luminescence spectra for discharge potentials of 13.500 volts, 9,600 volts, and 6,700 volts respectively. 

 Curves IV and V show, to a large scale, the luminescence spectra excited by ultra-violet light and 

 Roentgen rays respectively. 



induction coil, the primary of which was supplied with alternating current. 

 The discharge was made approximately unidirectional by placing a rectify- 

 ing tube in series. The current was controlled by an alcohol resistance. 

 The current used being smaller than that employed in our more recent 

 work, less difficulty was met with in maintaining constant pressure in the 

 tube. That the pressure was nearly constant during the measurements 

 corresponding to Fig. 147 is shown by the fact that it was possible to run 



' Nichols and Merritt, Physical Review, xxi, p. 247; xxu, p. 279; xxiii, p. 37; xxv, p. 362. 



