Endohedrally confined atoms in Fullerenes: He (and the time capsule)

DARIO MITNIK, JUAN RANDAZZO, FLAVIO COLAVECCHIA, Y GUSTAVO GASANEO

Valparaiso

Conferencia; V Encuentro Sud Americano de Colisiones Inelasticas en la Materia; 2010

Universidad Tecnica Federico Santa Maria

One of the most fascinating features of the fullerene molecules is that they are capable of enclosing atoms in their hollow interior, forming endohedrally confined atoms. Experimental efforts have made it possible to trap atoms inside a fullerene in different ways. The particular mechanisms responsiblefor the insertion of the atom, vary from a "brute force" implantation, to a "window" mechanism, in which high temperatures and pressures can break one of the Carbon-Carbon bonds in the cage. Small molecules and atoms can pass through this temporary hole, forming a stable endohedrally confined compound. The properties of a Helium atom confinedinside an endohedral cavity, like a fullerene, are studied. Thefullerene cavity is modeled by a potential well and the strength of this potential is varied in order to understand the collapse of different atomic wavefunctions into the fullerene cage.Three theoretical calculation methods have been developed: a relaxation method, a Sturmian basis method, and a variational method. The first two methods are nonperturbative. The three methods allow inclusion of full correlations among the two electrons. Results showing mirror collapse effects are presented for an S-wave model, in which all the angular quantum numbers are set to zero. In this work [2] we showed how the confinement potential strength affects in different amounts the atomic levels of the confined atom. Around the regions denoted as crossings, it seems that the variation in the potential produces degeneracies in energy, indicating that the levels can cross each to the other. A detailed analysis that requires a very high degree of precision shows that the energy levels do not cross each other, but rather come close and repel each other yielding to an avoided crossing. We analyzed the behaviour of the avoided crossing levels by using different information entropies, providing an efficient tool to estimate in a physically transparent manner the atomic transitions caused by a slowly varying perturbation.