Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase--relaxation width from the data on the excitation function oscillations in heavy--ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.