Intensity correlation speckles as a technique for removing Doppler
  broadening
  A method involving intensity correlation measurements is described, which
allows for the complete removal of Doppler broadening in the emission of
electromagnetic radiation from far-away sources that are inaccessible to
conventional Doppler-free measurements. The technique, relying on a correction
to g(2) of order N-1, probes the separation between neighboring spectral lines
and is also applicable to the elimination of broadening due to collisions (N is
the number of emitting particles and g(2) is the second-order field correlation
function). Possible applications include a determination of cosmological
parameters from red shifts of gravitationally-lensed quasars.
