1201 
the system are to be allowed, namely those for which the azimuthal 
impulse p has a value satisfying the conditions (97,6). In these the 
letter » represents a positive whole number, but ==0 which would 
be excluded according to SOMMERFEILD must also be admitted on the 
point of view explained in § 2. In the latter case the assumptions 
(9a) and (96) both give p=0O; hence 
ma as 
PD Me wit te Eer A 
in other words: the nuclei or “recoilrays’” as RuruerForp has called 
them, have for n=O the direction of the primary a-rays. 
$ 6. Recoil-rays of hydrogen. Whereas. the values (16) which 
obtain for n==0, hold generally for all kinds of atoms, the results 
are less general for n=—=1, 2 etc.; we shall only discuss the special 
case of the collision with a hydrogen atom. On the assumption (9a) 
we have according to (12) 
Ee. hv 
PGP rank wee) ond) SAS en rl) 
on assumption (95) 
= hv 
WPS Pr . t . . ‘ é + (18) 
In these expressions we may substitute 4 = 6.55 X 10-77 erg. sec. 
H= 4.7710—-' e.s. units e=2#; for v we shall take the velocity 
of the a-rays of RaC, for which RernerForD gives the value 
1.92.109 ¢™/,... we then obtain 
pty p = 13.8 hy or tg p= 4.40n ‘een eee, BETS) 
The first of these equations gives 
nl, @, = 842, u, == 0,;10'u,, == 0,001 Fe; 
n=2, g,=86°,50'", u,=0,055u,, R, = 0,0002 R- 
The velocities u,v, are computed from (15), the corresponding 
ranges A, 2, from the empirical equation R: R, = u*: wu’. 
Similarly the second hypothesis gives 
ei == 17% va RDR 
EN OOAD == 83 ION Ai OE Re 0 00NRE 
On the view that the particles can only move on the special 
orbits allowed by the quantum theory, we obtain the following 
result: a portion of the recoil rays are emitted in the direction of 
the primary rays (n=O); besides there are only particles which 
start at considerable angles to that direction, the smallest angle in 
