Hypermetallic dilithium fluoride, Li2F, and its cation and anion: a combined dissociation and charge permutation study

Dilithium fluoride, Li-F-Li, has been produced in the gas phase by neutrali zation of the Li2F+ cation, generated by fast atom bombardment ionization o f lithium trifluoroacetate. Subsequent reionization after similar to 0.2 mu s conclusively shows that the hypermetallic fluoride Li2F has survived int act and, thus, exists as a bound species. Charge reversal of Li,FC reveals that the anion Li2F- is stable also. These results are in agreement with pr evious results of ab initio calculations which predict considerable binding energies (greater than or equal to 129 kJ mol(-1)) for radical Li2F and an ion Li2F- both of which violate the octet rule. Collisionally excited Li2F cations dissociate to Li+, LiF+., Li-2(+), and F+ fragments. The yield of F+ strongly depends on the collision gas used, maximizing with He and Ne ta rgets whose ionization energies lie above that of the fluorine atom. (C) 19 99 Elsevier Science B.V.