is: a state of a composite system in which the components of the system may be arbitrarily far apart and in which their separation may be altered by an infinitesimal change in the energy.
is: in Schrödinger's model of the hydrogen atom, one of the states whose energy belongs to the continuum of energy levels above the ionization level, and in which the electron is freed from the atom. [P8.2]
is reached: when an electron from one of the bound states in the atom is given enough energy so that its energy becomes positive thus exceeding the zero energy that is conventionally assigned to the ionization level. [P8.2]
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