  In an electronic decay process followed by fragmentation the kinetic energy
release and electron spectra can be measured. Classically they are the mirror
image of each other, a fact which is often used in practice. Quantum
expressions are derived for both spectra and analyzed. It is demonstrated that
these spectra carry complementary quantum information and are related to the
nuclear dynamics in different participating electronic states. Illustrative
examples show that the classical picture of mirror image can break down and
shed light on the underlying physics.
