POSITRONIC WATER, a molecule consisting of an oxygen atom bonded to two positronium (Ps) atoms (each consisting of a positron and an electron bound together) instead of hydrogen atoms (proton-electron systems), has been predicted to exist by researchers (David Schrader, Marquette University, 414-288-3332). Positronic water could prove to be a rich playground for exploring electromagnetic interactions between trios of charged particles; such interactions are much rarer in an ordinary atom or molecule since all of the charged particles outside the nucleus are electrons which repel one another. Using a "Monte Carlo" technique that analyzed the various configurations of the 10 electrons and 2 positrons that would exist in a positronic water molecule, the researchers found that the energy associated with a positronic water molecule (abbreviated Ps₂O) is 1.27 eV less than that for a dissociated system of Ps and PsO, suggesting that stable positronic water can be formed, although with chemical bonds about 4 times weaker than those which exist in water. The model predicts an average lifetime of 220 ps for a Ps₂O molecule. To realize this molecule experimentally, however, researchers need to create higher- concentration positron sources than presently available. To form Ps₂O one might shoot nanosecond-length pulses of cold positron beams onto a metal surface covered with a sprinkling of oxygen atoms. (Jiang and Schrader, Physical Review Letters, 7 December 1998.)