Long wave-length limit for photo-electric emission from caesium vapor.-Using a special quartz tube and taking precautions to avoid photo-electric emission from the electrodes, a narrow beam of nearly monochromatic light of gradually decreasing wave-length, was focused on the hot caesium vapor, and it was found that above 3220 A the emission was zero, between 3220 and 3145 A the emission changed linearly because of the width of the slit used, and below 3145 A the emission was practically constant. The mean, 3180 A, is taken as the critical wave-length. This is evidently identical with the convergence wave-length 3184.28 A, which is related to the ionization potential V{ according to the equation Vi=hc/e\{. Therefore the separation of an electron from a caesium atom requires the same amount of work whether produced by an impinging electron or by absorption of light.
The magnetic susceptibility of three very pure rare earth oxides, namely those of cerium, holmium and praseodymium, have been measured and found to be 0.14X10" 6 , 229X10~6, and 13.4 X10~6 dyne cm per gm respectively. The spectroscopic and atomic weight analyses for the purity of one of the elements have been checked by magnetic susceptibility measurements. The latter were found to be in good agreement with the former.Resolution numbers obtained from a theory based by Jakob Kunz on the anomolous Zeeman effect have been compared with magnetic susceptibilities obtained by the author in this and previous papers and found to be consistent therewith.
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