Laser desorption ionization (LDI) time-of-flight (TOF) mass spectroscopy of solid p-dimethylaminophenylpentazole (1) gives strong peaks of m/z -42 and -70. The -70 peak was identified by N-15 labeling of 1 to be the pentazolate anion (cyclo-N-5(_)) The pentazolate anion is formed by an electron attachment to I forming the corresponding radical anion followed by a decomposition into 4-N(CH3)(2)-C6H4. and (cyclo-N-5(-)). The LDI TOF experimental study also revealed that the (cyclo-N-5(-))is very stable. These conclusions are supported by QM calculations at the B3LYP/6-311+G(2df,p) level. (C) 2003 Elsevier B.V. All rights reserved.