Multiple electron capture, excitation, and fragmentation inC6+−C60collisions

Abstract

We present experimental and theoretical results on single-and multiple-electron capture, and fragmentation, in C 6+ + C 60 collisions at velocities in the v col = 0.05 − 0.4 a.u. range. We use time-of-flight mass spectrometry and coincidence detection of charged fragments to separate pure target ionization from processes in which the C 60 target is both ionized and fragmented. The coincidence technique allows us to identify different types of fragmentation processes such as C q+ 60 → C q+ 58 + C 2 and C q+ 60 → C (q−1)+ 58 + C + 2 . A quasimolecular approach is employed to calculate charge transfer and target excitation cross sections. First-order time-dependent perturbation and statistical methods are used to treat the postcollisional processes: the calculated rate constants for C 2 and C + 2 emission from the excited and charged fullerene are then used to evaluate the fragmentation dynamics. We show that the target ionization cross section decreases with the induced target charge state and the impact energy. C 2 emission from C q+ 60 is found to dominate when q 2 while C + 2 emission dominates when q 5, in agreement with the present and previous experimental results.

Knockout driven reactions in complex molecules and their clusters

“…To gain further insights into distant collisions dynamics, quantum chemical approaches are required. A full quantum chemical treatment of the collision is computationally too demanding for current computer technology, but quasimolecular approaches have been used for He 2+ + C 60 [73] and C 6+ + C 60 collisions [74]. There, the electronic structure of C 60 was described using an extension of the spherical jellium model by Puska and Nieminen [75].…”

Roadmap on dynamics of molecules and clusters in the gas phase

“…Statistical methodologies such as Weisskopf theory, the RRKM Theory of Unimolecular Reactions and Microcanonical Metropolis Monte Carlo method also play a key role in the investigation of fragmentation processes due to significantly reduced computational cost with respect to molecular dynamics. In the study of C 6+ collisions with C 60 [133], the rate constants for C 2 and C + 2 emission from the excited and charged fullerene were calculated within the Weisskopf formalism and subsequently used to evaluate the fragmentation dynamics. The fundamental RRKM theory is widely applied in photodissociation or thermal decomposition studies to predict molecular fragmentation rate constants.…”

“…Experimental observations have indicated production of metastable species surviving on the microsecond timescale before the fragmentation, e.g. in C 6+ -C 60 collisions [133]. Hence, from a theoretical perspective, there is a need of new, reliable statistical methodologies that could explain such processes on an appropriate timescale.…”

A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

“…Till date, a number of theoretical and experimental investigations have been carried out using photons, 1-5 electrons, [6][7][8] and heavy ions [9][10][11][12] as probes to understand the breakup dynamics of molecules including, large biomolecules [13][14][15][16] or even free fullerene. [17][18][19][20][21] To tackle the complexity involved in the molecular break-up processes, it is necessary to have sophisticated, state-of-the-art, theoretical models and highly differential experimental measurements. Ion imaging is one of such front-line experimental techniques which has revolutionized the field of atomic and molecular physics as well as chemical physics.…”