Number 126 (Story #1), April 28, 1993 by Phillip F. Schewe and Ben Stein A NEW VERSION OF YOUNG'S INTERFERENCE EXPERIMENT , using not a pair of slits in a screen but instead a pair of mercury ions in an atom trap to scatter light waves and produce interference fringes, has been performed by a group at NIST in Boulder, Colorado. The researchers used a single laser beam both to cool (to mK temperatures) the ions, which are held in the inhomogeneous electric fields of a Paul trap, and to serve as a light source for producing interference effects. Stable fringe patterns were produced for several relative spacings (typically a few microns) for the ions. The fringe pattern, in turn, may be used as a diagnostic for measuring the temperature or spacing of ions in various trap experiments. (Phys. Rev. Lett., 19 April 1993; contact Ulli Eichmann of NIST at 303-497-7374).