396 Dr. N. Bolir on the Quantum Tlteory of 



A. An atomic system possesses a number of states in 



which no emission of energy radiation takes place, 

 even if the particles are in motion relative to each 

 other, and such an emission is to be expected on 

 ordinary electrodynamics. The states are denoted 

 as the " stationary " states of the system under 

 consideration. 



B. Any emission or absorption of energy radiation will 



correspond to the transition between two stationary 

 states. The radiation emitted during such a transi- 

 tion is homogeneous and the frequency v is deter- 

 mined by the relation 



hv = A 1 — A 2 , (1) 



where h is Planck's constant and A x and A 2 are the 

 energies of the system in the two stationary states. 



0. That the dynamical equilibrium of the systems in the 

 stationary states is governed by the ordinary laws 

 of mechanics, while these laws do not hold for the 

 transition from one state to another. 



D. That the various possible stationary states of a system 

 consisting of an electron rotating round a positive 

 nucleus are determined by the relation 



T = inha>, (2) 



where T is the mean value of the kinetic energy of 

 the system, co the frequency of rotation, and n a 

 whole number. 



It will be seen that these assumptions are closely analogous 

 to those originally used by Planck about the emission of 

 radiation in quanta, and about the relation between the 

 frequency of an atomic resonator (of constant frequency) 

 and its energy. It can be shown that, for any system con- 

 taining one electron rotating in a closed orbit, the assumption 

 C and the relation (2) will secure a connexion between the 

 frequency calculated by (1) and that to be expected from 

 ordinary electrodynamics, in the limit where the difference 

 between the frequency of the rotation of the electron in 

 successive stationary states is very small compared with the 

 absolute value of the frequency (see IV. p. 310). On the 

 nucleus theory this occurs in the region of very slow 

 vibrations. If the orbit of the electron is circular, the 

 assumption D is equivalent to the condition that the angular 

 momentum of the system in the stationary states is an 

 integral multiple of liftir. The possible importance of the 



