﻿164 
  ANNUAL, 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  charges. 
  In 
  flame 
  spectra 
  certain 
  lines 
  and 
  bands 
  of 
  an 
  element 
  

   are 
  conspicuous, 
  but 
  these 
  are 
  comparatively 
  few, 
  and 
  many 
  others 
  

   are 
  faint 
  or 
  lacking. 
  In 
  the 
  arc 
  the 
  flame 
  lines 
  remain, 
  but 
  the 
  

   emphasis 
  may 
  fall 
  on 
  quite 
  different 
  individual 
  lines. 
  Many 
  more 
  

   spectrum 
  lines 
  make 
  their 
  appearance. 
  Again, 
  in 
  the 
  spark 
  still 
  

   another 
  rearrangement 
  of 
  intensities 
  appears. 
  Prominent 
  flame 
  and 
  

   arc 
  lines 
  grow 
  faint 
  and 
  new 
  lines 
  are 
  found. 
  Thus 
  differences 
  in 
  

   spectra 
  of 
  the 
  same 
  chemical 
  element 
  which 
  are 
  produced 
  experi- 
  

   mentally 
  depend 
  on 
  the 
  degree 
  of 
  excitation. 
  

  

  According 
  to 
  Bohr's 
  theory 
  of 
  the 
  atom, 
  when 
  an 
  orbital 
  electron 
  is 
  

   driven 
  from 
  its 
  neutral 
  position 
  by 
  the 
  excitation 
  of 
  high 
  tempera- 
  

   ture 
  or 
  electrical 
  discharge, 
  it 
  may 
  migrate 
  to 
  one 
  or 
  another 
  of 
  

   certain 
  orbits, 
  determined 
  by 
  limitations, 
  depending 
  on 
  Planck's 
  

   theory 
  of 
  the 
  so-called 
  " 
  quantum," 
  that 
  unit 
  of 
  energy 
  which 
  crops 
  

   up 
  so 
  widely 
  in 
  physics, 
  as 
  readers 
  of 
  Millikan's 
  article 
  in 
  this 
  

   report 
  for 
  1918 
  are 
  aware. 
  In 
  each 
  of 
  these 
  possible 
  orbits 
  the 
  elec- 
  

   tron 
  has 
  a 
  definite 
  energy. 
  Returning 
  to 
  its 
  normal 
  place 
  from 
  one 
  

   of 
  these 
  excursions, 
  the 
  electron 
  from 
  an 
  outer 
  to 
  an 
  inner 
  orbit 
  

   gives 
  up 
  the 
  difference 
  between 
  the 
  definite 
  energies 
  appropriate 
  to 
  

   the 
  two 
  situations 
  and 
  thereby 
  gives 
  rise 
  to 
  radiation 
  in 
  a 
  specific 
  

   spectrum 
  line. 
  If 
  the 
  electron 
  temporarily 
  occupies 
  successively 
  sev- 
  

   eral 
  orbits 
  during 
  its 
  return, 
  several 
  spectrum 
  lines 
  are 
  formed 
  cor- 
  

   responding 
  in 
  the 
  frequency 
  of 
  their 
  vibrations 
  to 
  the 
  several 
  definite 
  

   differences 
  of 
  energy 
  involved. 
  The 
  actual 
  spectrum 
  at 
  a 
  given 
  in- 
  

   stant 
  is 
  the 
  joint 
  result 
  of 
  all 
  the 
  electronic 
  excursions 
  of 
  all 
  the 
  

   atoms 
  involved. 
  

  

  The 
  difference 
  between 
  arc 
  spectra 
  and 
  spark 
  spectra 
  is 
  explained 
  

   as 
  follows: 
  In 
  arc 
  spectra 
  the 
  lines 
  are 
  supposed 
  to 
  be 
  produced 
  by 
  

   the 
  migrations 
  of 
  single 
  electrons 
  displaced 
  from 
  each 
  of 
  the 
  par- 
  

   taking 
  atoms. 
  In 
  spark 
  spectra 
  two 
  electrons 
  may 
  be 
  removed, 
  one 
  

   to 
  a 
  great 
  distance. 
  This 
  one 
  is 
  that 
  which 
  took 
  part 
  in 
  arc 
  spec- 
  

   trum 
  phenomena. 
  It 
  is 
  assumed 
  to 
  be 
  eliminated 
  from 
  the 
  system. 
  

   But 
  the 
  second 
  electron 
  in 
  falling 
  back 
  to 
  its 
  position 
  produces 
  a 
  

   similar 
  series 
  of 
  spectrum 
  effects, 
  but 
  involving 
  different 
  amounts 
  of 
  

   energy, 
  and 
  thus 
  different 
  frequencies 
  of 
  vibration 
  for 
  the 
  lines 
  pro- 
  

   duced. 
  These 
  new 
  spectrum 
  lines 
  are 
  then 
  associated 
  with 
  the 
  second 
  

   displaced 
  electron 
  and 
  with 
  the 
  twice-shorn 
  remainder 
  of 
  the 
  atomic 
  

   structure. 
  As 
  the 
  new 
  energies 
  involved 
  greatly 
  exceed 
  the 
  old, 
  the 
  

   frequencies 
  of 
  vibration 
  are 
  correspondingly 
  enhanced, 
  so 
  that 
  on 
  the 
  

   whole 
  the 
  new 
  lines 
  lie 
  toward 
  the 
  violet 
  of 
  the 
  old, 
  and 
  may 
  even 
  lie 
  

   beyond 
  the 
  region 
  of 
  experimentation. 
  

  

  Complicated 
  and 
  hypothetical 
  as 
  all 
  this 
  may 
  seem 
  with 
  so 
  inade- 
  

   quate 
  a 
  presentation 
  as 
  the 
  above, 
  yet 
  remarkable 
  predictions 
  have 
  

   been 
  made 
  thereby 
  which 
  were 
  later 
  experimentally 
  verified 
  with 
  

  

  