Molecular Exciton Microscopy


          From Washington Post on 5 Feb. 90 via Dallas News Paper
         Scientist’ experiments focus on making better microscope

          Scientists have achieved the first step toward the invention
     of an  entirely new kind of microscope that they predict could be
     able to see objects as small as  the  individual  molecules  in a
     living cell.

          While the electron microscope can see molecules, it will not
     work on living subjects at normal temperatures and pressures.

          The new  procedure,  called “molecular exciton  microscopy,”
     promises to  do  this because it uses a modified form of ordinary
     light.   The smallest object visible  with  a light microscope is
     roughly the  size  of the shortest wavelength of  visible  light,
     which is blue and measures about 400 nanometers (a nanometer is a
     billionth of a meter).

          This is   small,   but  still  so  big  that  a  single  ray
     illuminates manymolecules at one  time, masking differences.  The
     new method, reported in the Journal of Science by  Aaron Lewis of
     Hebrew University   in   Jerusalem  and  Raoul  Kopelman  of  the
     University of Michigan and their colleagues, squeezes light waves
     into far smaller dimensions.

          They did  it  by shining light  through  a  funnel  with  an
     extremely tiny tip.  When photons, particles of  light, reach the
     tip, they  are  absorbed  by a crystal of anthracene.  Inside the
     crystal, the  photons  become  excitons   (a  combination  of  an
     electron and  a “hole,” an electrically charged void).   Excitons
     are far,  far  smaller than an atom.  As they emerge from the tip
     of the funnel, they are reborn as photons.

                                           contributed by Ron Moore