The Electron Bubble and the $H{e}_{60}$ Fullerene: A First-Principles Approach

Helium has a light atomic mass and, as a closed shell element, shows minimal interaction with other particles of the environment. Such properties favor the capture of an electron by liquid helium, leading to the formation of an electron bubble. The helium bubbles are of theoretical importance since different levels of quantum mechanical models can be tested for the correct prediction of a single quantum particle trapped in a cage. In this work, we propose a first-principles model of the electron bubble that takes, for the first time, the electronic structure of the cage into consideration. The model consists of a fullerene-type cage made of He atoms with an additional electron. The solution of the many-body Schroedinger equation is then performed using density functional theory, with a small and an extra-large atomic basis set. Several major improvements over the model of a particle in a rigid or soft spherical potential are assessed in this way, such as the localization and delocalization of the electron in the helium bubble, the transition of the electron to the continuum, the polarization of the He atoms building the wall, the ionic state of the electron bubble, besides the determination of relations of the volume-pressure type.