EXPERIMENTAL-EVIDENCE FOR THE EXISTENCE OF THE 2P-SIGMA BOUND-STATE OF HEH(2+) AND ITS DECAY MECHANISM

Experimental evidence for the existence of a bound state of HeH2+ is p resented. Bates and Carson predicted a bound 2psigma state of this thr ee-body system in spite of the strong repulsion between the nuclei. De cay is expected by electronic transition to the 1ssigma repulsive grou nd state with a mean lifetime of approximately 1 nsec. A novel coincid ence technique was developed for measurements of long lived molecular ions which dissociate in flight to the detector using a small powerful magnet to analyze the ions within a few nanoseconds. Coincidences bet ween the fragments detected at the deflection angle associated with He H2+ indicate clearly that a bound state was formed during the collisio n and decayed after the analyzer.