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  702 
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  LVII. 
  Scattering 
  of 
  a 
  Particles 
  by 
  Gases. 
  By 
  Professor 
  

   E. 
  Rutherfokd, 
  F.R.S., 
  and 
  J. 
  M. 
  Nuttall, 
  M.Se.* 
  

  

  THE 
  scattering 
  of 
  a 
  particles 
  by 
  matter 
  has 
  been 
  examined 
  

   in 
  detail 
  by 
  the 
  scintillation 
  method 
  by 
  Geiger 
  j 
  and 
  

   by 
  Geiger 
  and 
  Marsden 
  |. 
  In 
  the 
  experiments 
  of 
  Geiger, 
  

   the 
  most 
  probable 
  angle 
  through 
  which 
  an 
  oc 
  particle 
  was 
  

   scattered 
  was 
  determined 
  by 
  the 
  scintillation 
  method 
  for 
  

   different 
  thicknesses 
  of 
  a 
  number 
  of 
  elements. 
  It 
  was 
  found 
  

   that 
  the 
  most 
  probable 
  angle 
  of 
  scattering 
  for 
  thicknesses 
  

   of 
  different 
  elements, 
  equivalent 
  in 
  stopping 
  power 
  of 
  the 
  

   ol 
  particle 
  to 
  one 
  centimetre 
  of 
  air, 
  was 
  proportional 
  to 
  the 
  

   atomic 
  weight 
  of 
  the 
  scattering 
  element. 
  A 
  systematic 
  in- 
  

   vestigation 
  was 
  later 
  made 
  by 
  Geiger 
  and 
  Marsclen 
  of 
  the 
  

   " 
  large 
  angle 
  scattering 
  " 
  by 
  thin 
  films 
  of 
  matter. 
  The 
  

   results 
  were 
  shown 
  to 
  be 
  in 
  complete 
  accordance 
  with 
  the 
  

   theory 
  of 
  "single" 
  scattering 
  advanced 
  by 
  Rutherford 
  §. 
  

   This 
  theory 
  supposes 
  that 
  the 
  atom 
  consists 
  of 
  a 
  charged 
  

   nucleus 
  surrounded 
  by 
  a 
  compensating 
  distribution 
  of 
  elec- 
  

   trons. 
  The 
  large 
  angle 
  scattering 
  is 
  due 
  to 
  the 
  passage 
  of 
  

   the 
  a 
  particle 
  through 
  the 
  intense 
  electric 
  field 
  of 
  the 
  

   nucleus. 
  It 
  was 
  deduced 
  by 
  Rutherford, 
  and 
  Geiger 
  and 
  

   Marsden, 
  that 
  the 
  charge 
  on 
  the 
  nucleus 
  for 
  atoms 
  between 
  

   carbon 
  and 
  gold 
  was 
  approximately 
  proportional 
  to 
  the 
  

   atomic 
  weight, 
  and 
  was 
  equal 
  to 
  ^A<?, 
  where 
  A 
  is 
  the 
  atomic 
  

   weight 
  in 
  terms 
  of 
  that 
  of 
  hydrogen 
  and 
  e 
  is 
  the 
  electronic 
  

   charge. 
  On 
  this 
  theory 
  it 
  is 
  to 
  be 
  anticipated 
  that 
  hydrogen 
  

   has 
  a 
  nucleus 
  of 
  one 
  charge, 
  helium 
  of 
  two, 
  and 
  carbon 
  of 
  

   about 
  six. 
  

  

  As 
  this 
  deduction 
  is 
  of 
  great 
  importance 
  in 
  connexion 
  

   with 
  the 
  constitution 
  of 
  the 
  simpler 
  atoms, 
  experiments 
  were 
  

   undertaken 
  to 
  determine 
  the 
  scattering 
  of 
  a 
  particles 
  by 
  the 
  

   simple 
  gases. 
  The 
  method 
  employed 
  by 
  Geiger 
  and 
  Marsden 
  

   for 
  solids 
  is 
  not 
  altogether 
  suitable 
  for 
  gases 
  ; 
  in 
  addition, 
  

   the 
  large 
  angle 
  scattering 
  to 
  be 
  expected 
  for 
  the 
  light 
  

   elements 
  is 
  exceedingly 
  small, 
  and 
  would 
  be 
  difficult 
  to 
  

   measure 
  with 
  accuracy. 
  

  

  In 
  some 
  preliminary 
  experiments, 
  the 
  a 
  particles 
  were 
  

   made 
  to 
  pass 
  between 
  two 
  parallel 
  plates, 
  placed 
  a 
  small 
  dis- 
  

   tance 
  apart, 
  and 
  the 
  number 
  of 
  issuing 
  particles 
  were 
  observed 
  

   (1) 
  in 
  a 
  vacuum 
  and 
  (2) 
  when 
  the 
  space 
  between 
  the 
  plates 
  

   was 
  filled 
  with 
  gas 
  at 
  a 
  known 
  pressure. 
  The 
  number 
  of 
  

   a 
  particles 
  was 
  counted 
  photographically, 
  using 
  a 
  string- 
  

   electrometer. 
  On 
  account, 
  however, 
  of 
  the 
  probability 
  

  

  * 
  Communicated 
  by 
  the 
  Authors. 
  

  

  t 
  H. 
  Geiger, 
  Proc. 
  Roy. 
  Soc. 
  lxxxi. 
  p. 
  174 
  (1908). 
  

  

  i 
  H. 
  Geiger 
  and 
  E. 
  Marsden, 
  Phil. 
  Mag. 
  xxv. 
  p. 
  604 
  (1913). 
  

  

  § 
  E. 
  Rutherford, 
  Phil. 
  Mag. 
  xxi. 
  p. 
  669 
  (1911). 
  

  

  