﻿290 Mr. R. D. Kleeman on the Recombination 



electrons can be displaced only in certain directions, and 

 when an electron is displaced beyond a certain point, the 

 direction o£ the forces acting on it, due to the other electrons 

 and positive charge of molecule, will be such as to eject it 

 from the molecule. 



The electron would then derive, in part at least, its energy 

 from the potential energy of the molecule. 



This would account for the great penetrating power of the 

 electrons ejected from molecules ionized by X rays. 



§m. 



For investigating the initial recombination of ions made 

 by /3 rays, the (3 rays of uranium oxide were used. 



About 30 gins, of uranium oxide were spread uniformly in 

 a shallow metal dish, and covered with a sheet of aluminium 

 of '21 mm. thickness. This thickness of aluminium was 

 sufficient to stop all the a particles. 



This dish fitted into the chamber used in the previous 

 experiments. 



The electrode was raised by means of its supporting screws 

 till the distance from the aluminium plate was "5 cm. 



Table VII. gives some of the readings obtained. 



It appears from these readings that there is little initial 

 recombination of ions in a gas ionized by /3 rays. 



This result might have been expected, since the secondary 

 /3 rays from a solid have considerable penetrating power, and 

 there is no reason why molecules should behave differently 

 in the gaseous state. 



An experiment was also carried out to test whether the 

 ions made by /3 rays that had been allowed to pass through 

 a considerable thickness of aluminium, showed greater initial 

 recombination than before. The observations (see Table VII.) 

 showed that there is still little initial recombination. 



This probably means that, since initial recombination in 

 the case of the <x particle depends on its velocity, as will be 

 shown further on, the rays which penetrated the aluminium 

 plate suffered scarcely any decrease in velocity, and therefore 

 the absorption of /3 rays by a slab of matter consists more in 

 the deflexion of the rays than absorption of their energy. 



§IV. 



The initial recombination of ions made by 7 rays was next 

 investigated, the same ionization chamber as before being 

 used. 



The electrode was raised till it occupied the middle of the 



