A continuous neat ammonia cluster beam was ionized by electron impact ionization, then analyzed by a tandem triple quadrupole mass spectrometer. Metastable Coulomb explosion was observed for the {NH3}(51)H-x=0,1,2(2+) and the {NH3}(53)H-X=0,1,2(2+) cluster ions. Coulomb explosion was observed in larger doubly charged cluster ions activated by low energy collisions with argon gas. (C) 1997 American Institute fo Physics.