﻿326 
  The 
  X-Ray 
  Spectra 
  and 
  Constitution 
  of 
  the 
  Atom. 
  

  

  Andrade 
  *, 
  which 
  forms 
  a 
  mixture 
  of 
  RaB 
  and 
  RaC, 
  might 
  

   be 
  accounted 
  for 
  by 
  assuming 
  an 
  electron 
  to 
  recombine 
  

  

  between 
  circles 
  with 
  angular 
  momenta 
  ^ 
  ^r— 
  and 
  7; 
  77—- 
  

  

  b 
  Z7T 
  2?r 
  

  

  Let 
  more 
  generally 
  an 
  electron 
  pass 
  from 
  a 
  circle 
  with 
  

  

  angular 
  momentum 
  — 
  x— 
  to 
  one 
  with 
  a 
  momentum 
  — 
  ^— 
  . 
  

   m 
  Zir 
  m2ir 
  

  

  If 
  we 
  take 
  into 
  account 
  the 
  variation 
  of 
  mass 
  with 
  velocity, 
  

  

  we 
  get 
  

  

  £ 
  =(N 
  + 
  l)w(i 
  s 
  - 
  i) 
  {! 
  + 
  {(* 
  + 
  !)(£ 
  + 
  £)}. 
  (28) 
  

   Putting 
  N 
  = 
  82, 
  m=6, 
  w 
  x 
  = 
  3, 
  n 
  2 
  =-&, 
  we 
  get 
  

  

  ^=1'23.10 
  4 
  , 
  

   while 
  the 
  observed 
  wave-length 
  gives 
  

  

  ^=1-26.10 
  4 
  . 
  

  

  The 
  numerical 
  agreement 
  is 
  good 
  enough, 
  but 
  I 
  think 
  we 
  

   must 
  be 
  very 
  careful 
  in 
  drawing 
  conclusions 
  from 
  a 
  single 
  

   coincidence. 
  I 
  merely 
  put 
  it 
  down 
  as 
  a 
  suggestion 
  which 
  

   might 
  be 
  worth 
  consideration. 
  

  

  Recent 
  experiments 
  of 
  Barkla 
  and 
  Miss 
  White 
  have 
  given 
  

   indications 
  of 
  a 
  homogeneous 
  J-radiation 
  more 
  penetrating 
  

   than 
  the 
  K-radiation, 
  which 
  Barkla 
  calls 
  the 
  Y-series. 
  From 
  

   the 
  absorption 
  coefficient 
  of 
  the 
  rays 
  just 
  hard 
  enough 
  to 
  

   excite 
  the 
  J-radiation 
  they 
  find 
  for 
  Al 
  a 
  wave-length 
  

  

  \=0'37.10- 
  8 
  cm. 
  

  

  If 
  this 
  series 
  really 
  exists 
  it 
  can 
  hardly 
  be 
  explained 
  by 
  

   electrons 
  belonging 
  to 
  the 
  external 
  system, 
  but 
  should 
  be 
  

   produced 
  by 
  the 
  electrons 
  forming 
  part 
  of 
  the 
  nucleus. 
  

   The 
  equation 
  (28) 
  would 
  give 
  nearly 
  the 
  right 
  frequency 
  

   when 
  we 
  put 
  

  

  m 
  = 
  4, 
  Wi 
  = 
  l, 
  and 
  w 
  2 
  = 
  2. 
  

  

  Physical 
  Institute, 
  Christiania. 
  

   December 
  14, 
  1917. 
  

  

  * 
  E. 
  Kutherford 
  and 
  E. 
  N. 
  da 
  C. 
  Andrade, 
  Phil. 
  Mag. 
  xxviii. 
  p. 
  263 
  

   (1914). 
  

  

  