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Abstract
The correlated motion of the three body Coulomb interacting system $\rm H\sp{+} + H\sp{+} + H\sp{-},$ produced in collisions of 4 keV H$\sb3\sp+$ with a He target gas cell, is observed in a triple coincidence experiment. Because the three fragments interact via long range Coulomb forces, the motion of the $\rm H\sp+ + H\sp+ + H\sp{-}$ system can be highly correlated.
Using a two-stage parallel plate energy analyzer equipped with position sensitive detectors, the laboratory frame energy and emission angle of each of the three particles is measured simultaneously in a triple coincidence experiment. Transforming from laboratory frame to the center of mass (c.m.) frame of the $\rm H\sp+ + H\sp+ + H\sp-$ system, the c.m. energy of each particle and the correlation angle $\phi\sb{12}$, the angle between the c.m. frame momenta of the two protons, are determined for each $\rm H\sp+ + H\sp+ + H\sp-$ detected in triple coincidence. The total c.m. energy $\varepsilon\sb{t}$ available to the three particles as kinetic energy is in the few eV range.
The highly correlated motion of the $\rm H\sp+ + H\sp+ + H\sp-$ system, reflected in the sharing of $\varepsilon\sb{t}$ among the three fragments and in the correlation angle $\phi\sb{12}$, is illustrated with the use of a Dalitz plot.
