Locking a molecular bond: A case study of CsI

This paper treats the problem of locking a molecular bond at a length other than the equilibrium distance, with the help of optical electric fields. Locking conditions for single-color fields are examined, and slowly decaying locked wave functions are sought. These wave functions are then used as target functions in an optimal control procedure. The resultant solution is an optimal field that creates a wave function as close as possible to the target function, followed by the application of a locking single-color field that can keep a large part of this wave function at the given position. An objective of the approach is to eventually extend the optimal control theory to the preparation of molecules in quasistationary nonequilibrium states for further study by spectroscopic or other means. Results are reported for a model of CsI with two potential-energy surfaces, one with a repulsive character.