[ 488 ] 



XLVI. Electronic Frequency and Atomic Number. By H. 

 Stanley Allen, M.A., B.Sc, University of London, 

 King's College*. 



§ 1. Introduction. 



IN a paper on the relation between atomic frequency and 

 atomic number t the writer has shown that the product 

 of Moseley's atomic number, N, and the characteristic 

 frequency, v, for an element in the solid state can be 

 expressed in the form 



where n is an integer and v A a fundamental frequency, which 

 is constant and equal to about 21'3 X 10 12 sec. -1 for metallic 

 elements. The object of the present paper % is to show that a 

 similar relation holds for certain electronic frequencies, but 

 when the vibration of an electron is in question, it is necessary 

 to replace the constant v A by the fundamental electronic 

 frequency, v E = 3*289 x 10 15 sec. -1 , which is Bydberg's con- 

 stant in spectral series usually expressed as the wave-number 

 109679-22 (Curtis). The relation then takes the form 



Nv = nj/ E , or Nj/ = (w + J)v E . 



In these cases, as in the case of the characteristic atomic 

 frequency, v refers to some limiting frequency or to a 

 frequency associated with a maximum value of some variable 

 quantity. 



§ 2. 7 he Maximum of the Photoelectric Effect, 



When a photoelectric current is produced by light in 

 which the electric vector is parallel to the plane of inci- 

 dence, the curve showing the relation between the photo- 

 electric activity and the wave-length has a maximum for a 

 particular value of the wave-length. According to Pohl and 

 Pringsheini § this " selective " effect has been established 

 with certainty only in the case of the alkali metals. The 

 value of the wave-length corresponding to the maximum has 

 been determined by these investigators with an accuracy of 

 about 2 or 3 per cent. The results have been employed in 

 the construction of Table I., which gives the value of v and 

 of Nv for the four alkali metals examined. 



* Communicated by the Author, 

 f Supra, p. 478. 



X A preliminary account of the results has been given in a paper read 

 before the Koyal Society, Nov. 1st, 1917.. 



§ Die lichtelektrischen Erscheinungen (Vieweg, 1914). 



