Ionization probability of the hydrogen atom suddenly released from confinement Morcillo M F, Alcaraz-Pelegrina J M, Sarsa A ∗ October 13, 2017 Abstract The problem of the stability of a confined atom when it is extracted from the confining cavity has been investigated, modeled by a spherical hard wall potential. The ionization probability when the atom is released from confinement has been obtained. The dependence of the ionization probability on the confinement radius and on the quantum numbers of the initial confined state has been studied. The probability density function of the ionization energy of the ejected electron has been obtained for the different cases considered. The oscillatory structure of this distribution function, with a principal maximum located in the neighborhood of the energy of the initial state and minima very close to zero has been elucidated. The sudden approximation has been applied and the analytic continuation method has been used to calculate the different stationary states. Keywords confined atoms, ionization probability, ionization energy distribution function, sudden ap- proximation. * Departamento de F´ ısica, Campus de Rabanales Edif. C2, Universidad de C´ordoba, E-14071 C´ordoba, Spain email: fa1sarua@uco.es 1