MEAN-LIFETIME CALCULATIONS OF THE METASTABLE DOUBLY-CHARGED NEAR2-GASDIMER( RARE)

The energies and mean lifetimes of the different vibrational states of the 1SIGMA+ electronic ground state of NeAr2+ have been calculated us ing the phase-shift technique. An efficient searching method for these narrow resonances was developed. The calculated lifetime of the upsil on = 12 vibrational state is in reasonable agreement with the experime ntal value of 275+/-25 nsec, reported recently by Ben-Itzhak, Gertner, and Rosner [Phys. Rev. A 47, 289 (1993)], while the lifetimes of othe r states are more than three orders of magnitude off, thus determining the long-lived vibrational state detected unambiguously. From the dif ference between the calculated and measured mean lifetime, we have est imated that the potential curve of this 26-electron system is accurate to a few meV. We have also performed ab initio calculations of the 2S IGMA+ electronic ground state of NeAr+ and calculated the Franck-Condo n factors for the final vibrational-state distribution of the NeAr2+ m olecular ion produced in the NeAr+ charge-stripping collisions in orde r to estimate that high vibrational states are indeed produced in the experiment. We have also examined the validity of the WKB method for c alculating the lifetimes of highly excited vibrational states.