Formation of the trimer ion core in the heterogeneous rare gas cluster ions

Abstract

Thermochemical stabilities of the cluster ions composed of mixed rare gases were measured using a pulsed-electron beam high pressure mass spectrometer. The formation of trimer ion cores, i.e., A+(B)2 and A2+(B)1, was found when A and B are next to each other in the Periodic Table. This trend is similar to that for the pure rare gas cluster ions, i.e., the formation of ion core Rg3+ for Rg=He, Ne, Ar, Kr, and Xe. Although Ar and Xe are not next to each other in the Periodic Table, the formation of the trimer ion core is found for Xe+(Ar)2. This may be due to the fact that the ionization potentials of Ar and Xe are close to each other. The bond energies of larger cluster ions A+(B)2(B)n−2 and A2+(B)1(B)n−1 were found to be similar to those of homogeneous cluster ions (B)3+(B)n−3. The experimental bond energies were confirmed by ab initio calculations with a modified G2(MP2) method [e.g., 0.2 kcal/mol (expt) and 0.3 kcal/mol (theory) for Ar2+⋅He].