Coherent positronium molecule PSn and scanning clustering microscopy

The remarkable coherent features are indicated for the positronium molecules Ps(n), which are the lightest molecular system in the universe. The majority of Ps(n) molecules undergo the coherent annihilation of all constituent Ps atoms yielding the coherent n-pair photons which provide a unique method for observing Ps, with identifying the order of clustering rr. This leads to a new microscopy [scanning clustering microscopy(SCM)] in which Ps(n) molecules are formed from surface positrons and Ps swarmed around a fine tip of a probe electrically biased with respect to a contacting matter surface to be investigated. It would open up new broad fields to study dynamical aspects of surface layer such as the catalytic activity on a subatomic scale. A method based on the Hunbury Brown-Twiss effect is also presented to determine the dimensions of Ps(n). (C) 1999 John Wiley & Sons, Inc.