REARRANGEMENTS IN NEGATIVELY CHARGED AMMONIUM-NITRATE CLUSTERS

The sputtering of condensed-phase ammonium nitrate yields an extensive distribution of cluster ions with the general formula [NH4NO3)(n)NO3] -, where n 3 to >40. Only a very low relative abundance of the n land the n = 2 species are detected by mass spectrometry. Collision-induced dissociation experiments suggest that [NH4NO3)NO3]- rearranges to los e NH3 and form [H(NO3)(2)](-), which is detected at high relative abun dance. Gradient-corrected density functional calculations show that th ere is strong hydrogen bonding in NH4NO3 and essentially no hydrogen b onding in [NH4NO3)NO3](-). Thus, with a relatively small amount of int ernal energy the latter can rearrange to lose a neutral ammonia molecu le.