Mode excitation dynamics in the fragmentation of Ar4+: An helicity decoupling study.

A full quantum study of the fragmentation dynamics for argon trimer ions is carried out using a previously computed potential energy surface (PES). The initial and final internal states which are being considered are the bending–stretching states of the trimer and the rotovibrational states of the residual dimer ion. The treatment employs the helicity decoupling approximation over a broad range of total angular momentum values (J) and analyses the final distribution of rotational–vibrational states as a function of the metastable states of the J values and of the ‘‘tumbling’’ (helicity) quantum number Ω. It is found that at least two different effects, one mainly dynamically related to the centrifugal barrier and another to the orientational nature of the coupling potential field, can be discerned to explain the fragmentation results. [ABSTRACT FROM AUTHOR]