Shape change due to relaxation

In the second formal step of the process, the nuclear arrangement relaxes to a nearby minimum of the potential energy surface of the new electronic state. The three-dimensional body of the electron distribution "follows" the nuclear rearrangement, hence the shape of the electron distribution changes in this step too. This change is called the shape change due to relaxation. 

Quantum Chemical le Chatelier Principle for Molecular Shapes (QCLCP-MS) the shape change due to relaxation tends to reduce the effect of the initial vertical shape change. 

In other words, the initial vertical shape change in Step 1 may be regarded as a stress applied to the molecular system, and the system appears to readjust in Step 2 by the shape change due to relaxation in such a way that the overall shape change is reduced to less than that of the vertical shape change. 

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