Abstract: | Neutral benzene-ammonia clusters, prepared in a supersonic expansion, were ionized using multiphoton ionization. The cluster ions were investigated with a time-of-flight mass spectrometer. The observed major cluster ions, under 355-nm laser irradiation, resulting from prompt intracluster ion-molecule reaction and fragmentation following ionization are (C6H6)m(NH3)nH+, m = 1–6, n = 1–4 and (C6H6)m+, m = 1–3. The results of isotopic labeling experiments clearly indicate that C6H6 does not participate in intracluster ion-molecule reactions to form (C6H6)m(NH3)nH+. A local maximum appears at n = 2 in the intensity distribution of (C6H6)m(NH3) nH+ for each value of m under all experimental conditions. This finding indicates that (C6H6)m(NH3)2H+ is more stable than any other (C6H5)m(NH3)mH+ (n = 1,3,4) for m = 1–6. |