Artificial Disintegration oj Light Elements. 



815 



Curve A is for rays o£ range S'6 cm. Only the end part 

 of the curve is given, as the initial portions are complicated 

 by the effects of the a rays of range 5 cm. 



Curves B, C, D are for a rays of ranges 7*0, 6'0, and 

 4*9 cm. respectively. Curve E shows the natural effect 

 when the air is replaced by dry oxygen. It was found that 

 to a. first approximation the range of the liberated particles 

 was proportional to the range of the incident a. particles. 

 For example, the ranges of the particles were about 50, 40, 

 34 cm. for a particles of range 8'6, 7*0, and 6'0 respectively. 



Fig. 3. 







TROGt 

 8-6c~a( 





















A 



N 1 

 Particle. 

















\ 



B 

 C 



7-Oc~ - 



*9« - 



















\ E- Oxygen CuRvt 



















\ 



V 





















\ 





\ 























% 





\ 



















\ 



\ 



v \ 



-\ 



















*c 



\D 





sC 



\B^ 



""- 



^F 



\A 

























— . 



*••«» 



>^ 







/4 IS ZZ Z6 30 34 



ABSORPTION /ft CHS OF AIR 



4£ 



It is seen that the number of particles observed increased 

 rapidly with the velocity of the a particle. Allowing for 

 the natural scintillations given by curve E, the number 

 observed for 12 cm. absorption is 6*5, 3*4, 0'8 per milligram 

 for rays of range 7*0, 60, and 4'9 cm. respectively. The 

 corresponding numbers .for half the maximum range in each 

 case is 4*3, 2*5, and 0*7. It is to be remembered that the 

 a rays pass through a length of 3*5 cm. of gas, so that in 

 the case of a rays of initial range 7 cm., the gas is acted 

 on by rays varying in range from 7 to 3*5 cm. Without 

 definite information as to the angular distribution of the 

 particles liberated by the collisions, it is difficult to estimate 

 the number of particles provided by each part of the column 

 of gas traversed. It seems clear, however, that the number 

 rises rapidly with increase of velocity o^ the a rays. This 



