The eigenstates of a hydrogen atom are stationary states with definite values of energy. Now, as I understand it, the quantum mechanical state of the electron in the hydrogen atom is really a linear superposition of all these energy eigenstates. So this should mean that there is a finite probability of getting a higher energy value ( higher than the ground state energy value ) for any hydrogen atom, because the only thing that defines an hydrogen atom is the proton's coulomb field and the fact that it is a single electron system. So does that mean that there is no such thing as 'ground state' hydrogen ? At least not until after you've made an energy measurement on the system. Or does the lowest possible potential energy requirement force the electron to stay in the ground state ? How is this 'forced to stay in the ground state' condition realized through quantum theory? I remember reading somewhere that electrons in atoms always occupy stationary states. Is this true ? I was always under the impression that the general solution to the schrodinger equation is a linear superposition of stationary states.