﻿18 
  Dr. 
  N. 
  Bohr 
  on 
  the 
  Constitution 
  

  

  rather 
  few 
  lines 
  are 
  observed. 
  Now 
  in 
  Wood's 
  experiments 
  

   the 
  pressure 
  was 
  not 
  very 
  low, 
  and 
  the 
  states 
  corresponding 
  

   to 
  high 
  values 
  for 
  r 
  could 
  therefore 
  not 
  appear 
  ; 
  yet 
  in 
  the 
  

   absorption 
  spectrum 
  about 
  50 
  lines 
  were 
  detected. 
  Tn 
  the 
  

   experiments 
  in 
  question 
  we 
  consequently 
  observe 
  an 
  absorption 
  

   of 
  radiation 
  which 
  is 
  not 
  accompanied 
  by 
  a 
  complete 
  transition 
  

   between 
  two 
  different 
  stationary 
  states. 
  According 
  to 
  the 
  

   present 
  theory 
  we 
  must 
  assume 
  that 
  this 
  absorption 
  is 
  followed 
  

   by 
  an 
  emission 
  of 
  energy 
  during 
  which 
  the 
  systems 
  pass 
  back 
  

   to 
  the 
  original 
  stationary 
  state. 
  If 
  there 
  are 
  no 
  collisions 
  

   between 
  the 
  different 
  systems 
  this 
  energy 
  will 
  be 
  emitted 
  as 
  

   a 
  radiation 
  of 
  the 
  same 
  frequency 
  as 
  that 
  absorbed, 
  and 
  there 
  

   will 
  be 
  no 
  true 
  absorption 
  but 
  only 
  a 
  scattering 
  of 
  the 
  original 
  

   radiation 
  ; 
  a 
  true 
  absorption 
  will 
  not 
  occur 
  unless 
  the 
  energy 
  

   in 
  question 
  is 
  transformed 
  by 
  collisions 
  into 
  kinetic 
  energy 
  of 
  

   free 
  particles. 
  In 
  analogy 
  we 
  may 
  now 
  from 
  the 
  above 
  expe- 
  

   riments 
  conclude 
  that 
  a 
  bound 
  electron 
  — 
  also 
  in 
  cases 
  in 
  which 
  

   there 
  is 
  no 
  ionization 
  — 
  will 
  have 
  an 
  absorbing 
  (scattering) 
  

   influence 
  on 
  a 
  homogeneous 
  radiation, 
  as 
  soon 
  as 
  the 
  fre- 
  

   quency 
  of 
  the 
  radiation 
  is 
  greaier 
  than 
  W//i, 
  where 
  W 
  is 
  the 
  

   total 
  amount 
  of 
  energy 
  emitted 
  during 
  the 
  binding 
  of 
  the 
  

   electron. 
  This 
  would 
  be 
  highly 
  in 
  favour 
  of 
  a 
  theory 
  of 
  

   absorption 
  as 
  the 
  one 
  sketched 
  above, 
  as 
  there 
  can 
  in 
  such 
  a 
  

   case 
  be 
  no 
  question 
  of 
  a 
  coincidence 
  of 
  the 
  frequency 
  ol 
  the 
  

   radiation 
  and 
  a 
  characteristic 
  frequency 
  of 
  vibration 
  of 
  the 
  

   electron. 
  It 
  will 
  further 
  be 
  seen 
  that 
  the 
  assumption, 
  that 
  

   there 
  will 
  be 
  an 
  absorption 
  (scattering) 
  of 
  any 
  radiation 
  

   corresponding 
  to 
  a 
  transition 
  between 
  two 
  different 
  me- 
  

   chanical 
  stntes, 
  is 
  in 
  perfect 
  analogy 
  with 
  the 
  assumption 
  

   generally 
  used 
  that 
  a 
  free 
  electron 
  will 
  have 
  an 
  absorbing 
  

   (scattering) 
  influence 
  on 
  light 
  of 
  any 
  frequency. 
  Corre- 
  

   sponding 
  considerations 
  will 
  hold 
  for 
  the 
  emission 
  of 
  radiation. 
  

   In 
  analogy 
  to 
  the 
  assumption 
  used 
  in 
  this 
  paper 
  that 
  the 
  

   emission 
  of 
  line-spectra 
  is 
  due 
  to 
  the 
  re-formation 
  of 
  atoms 
  

   after 
  one 
  or 
  more 
  of 
  the 
  lightly 
  bound 
  electrons 
  are 
  removed, 
  

   we 
  may 
  assume 
  that 
  the 
  homogeneous 
  Rontgen 
  radiation 
  is 
  

   emitted 
  during 
  the 
  settling 
  down 
  of 
  the 
  systems 
  after 
  one 
  of 
  

   the 
  firmly 
  bound 
  electrons 
  escapes, 
  e.g. 
  by 
  impact 
  of 
  cathode 
  

   particles 
  *. 
  In 
  the 
  next 
  part 
  of 
  this 
  paper, 
  dealing 
  with 
  the 
  

   constitution 
  of 
  atoms, 
  we 
  shall 
  consider 
  the 
  question 
  more 
  

   closely 
  and 
  try 
  to 
  show 
  that 
  a 
  calculation 
  based 
  on 
  this 
  

   assumption 
  is 
  in 
  quantitative 
  agreement 
  with 
  the 
  results 
  of 
  

   experiments 
  : 
  here 
  we 
  shall 
  only 
  mention 
  briefly 
  a 
  problem 
  

   with 
  which 
  we 
  meet 
  in 
  such 
  a 
  calculation. 
  

  

  * 
  Compare 
  J. 
  J. 
  Thomson, 
  Phil. 
  Mag. 
  xxiii. 
  p. 
  456 
  (1912). 
  

  

  