﻿868 
  Dr. 
  N. 
  Bohr 
  on 
  the 
  Constitution 
  

  

  systems 
  considered 
  in 
  Part 
  II. 
  We 
  must 
  assume 
  that 
  the 
  

   systems 
  are 
  formed 
  by 
  the 
  interaction 
  of 
  others, 
  containing 
  

   single 
  nuclei, 
  which 
  already 
  have 
  bound 
  electrons. 
  We 
  

   shall 
  now 
  consider 
  this 
  problem 
  more 
  closely, 
  starting 
  with 
  

   the 
  simplest 
  possible 
  case, 
  viz., 
  the 
  combination 
  of 
  two 
  

   hydrogen 
  atoms 
  to 
  form 
  a 
  molecule. 
  

  

  Consider 
  two 
  hydrogen 
  atoms 
  at 
  a 
  distance 
  apart 
  great 
  in 
  

   comparison 
  with 
  the 
  linear 
  dimensions 
  of 
  the 
  orbits 
  of 
  the 
  

   electrons, 
  and 
  imagine 
  that 
  by 
  help 
  of 
  extraneous 
  forces 
  

   acting 
  on 
  the 
  nuclei, 
  we 
  make 
  these 
  approach 
  each 
  other 
  ; 
  

   the 
  displacements, 
  however, 
  being 
  so 
  slow 
  that 
  the 
  dynamical 
  

   equilibrium 
  of 
  the 
  electrons 
  for 
  every 
  position 
  of 
  the 
  nuclei 
  

   is 
  the 
  same 
  as 
  if 
  the 
  latter 
  were 
  at 
  rest. 
  

  

  Suppose 
  that 
  the 
  electrons 
  originally 
  rotate 
  in 
  parallel 
  

   planes 
  perpendicular 
  to 
  the 
  straight 
  line 
  connecting 
  the 
  

   nuclei, 
  and 
  that 
  the 
  direction 
  of 
  rotation 
  is 
  the 
  same 
  and 
  

   the 
  difference 
  in 
  phase 
  equal 
  to 
  half 
  a 
  revolution. 
  During 
  

   the 
  approach 
  of 
  the 
  nuclei, 
  the 
  direction 
  of 
  the 
  planes 
  of 
  

   the 
  orbits 
  of 
  the 
  electrons 
  and 
  the 
  difference 
  in 
  phase 
  will 
  

   be 
  unaltered. 
  The 
  planes 
  of 
  the 
  orbits, 
  however, 
  will 
  at 
  the 
  

   beginning 
  of 
  the 
  process 
  approach 
  each 
  other 
  at 
  a 
  higher 
  

   rate 
  than 
  do 
  the 
  nuclei. 
  By 
  the 
  continued 
  displacement 
  

   of 
  the 
  latter 
  the 
  planes 
  of 
  the 
  orbits 
  of 
  the 
  electrons 
  will 
  

   approach 
  each 
  other 
  more 
  and 
  more, 
  until 
  finally 
  for 
  a 
  

   certain 
  distance 
  apart 
  of 
  the 
  nuclei 
  the 
  planes 
  will 
  coincide, 
  

   the 
  electrons 
  being 
  arranged 
  in 
  a 
  single 
  ring 
  rotating 
  in 
  the 
  

   plane 
  of 
  symmetry 
  of 
  the 
  nuclei. 
  During 
  the 
  further 
  ap- 
  

   proach 
  of 
  the 
  nuclei 
  the 
  ratio 
  between 
  the 
  diameter 
  of 
  the 
  

   ring 
  of 
  electrons 
  and 
  the 
  distance 
  apart 
  of 
  the 
  nuclei 
  will 
  

   increase, 
  and 
  the 
  system 
  will 
  pass 
  through 
  a 
  configuration 
  

   in 
  which 
  it 
  will 
  be 
  in 
  equilibrium 
  without 
  the 
  application 
  

   of 
  extraneous 
  forces 
  on 
  the 
  nuclei. 
  

  

  By 
  help 
  of 
  a 
  calculation 
  similar 
  to 
  that 
  indicated 
  in 
  § 
  2, 
  

   it 
  can 
  be 
  simply 
  shown 
  that 
  at 
  any 
  moment 
  during 
  this 
  

   process 
  the 
  configuration 
  of 
  the 
  electrons 
  is 
  stable 
  for 
  a 
  

   displacement 
  perpendicular 
  to 
  the 
  plane 
  of 
  the 
  orbits. 
  In 
  

   addition, 
  during 
  the 
  whole 
  operation 
  the 
  angular 
  momentum 
  

   of 
  each 
  of 
  the 
  electrons 
  round 
  the 
  line 
  connecting 
  the 
  nuclei 
  

   will 
  remain 
  constant, 
  and 
  the 
  configuration 
  of 
  equilibrium 
  

   obtained 
  will 
  therefore 
  be 
  identical 
  with 
  the 
  one 
  adopted 
  

   in 
  § 
  3 
  for 
  a 
  hydrogen 
  molecule. 
  As 
  there 
  shown, 
  the 
  con- 
  

   figuration 
  will 
  correspond 
  to 
  a 
  smaller 
  value 
  for 
  the 
  total 
  

   energy 
  than 
  the 
  one 
  corresponding 
  to 
  two 
  isolated 
  atoms. 
  

   During 
  the 
  process, 
  the 
  forces 
  between 
  the 
  particles 
  of 
  the 
  

   system 
  will 
  therefore 
  have 
  done 
  work 
  against 
  the 
  extraneous 
  

   forces 
  acting 
  on 
  the 
  nuclei 
  ; 
  this 
  fact 
  may 
  be 
  expressed 
  by 
  

  

  ■ 
  

  

  