Laser control strategies for energy transfer reactions in atom molecule collisions

Abstract

We present schemes for the laser pulse control of bimolecular reactions. As a model system we treat the collision complex Na–H₂, which is unbound in the electronic ground state X²A₁ and weakly bound in the electronic excited state A²B₂. This system decays non-adiabatically from the excited state via a conical intersection back to the ground state. The objective of the laser controls presented is the excitation of the collision pair with simultaneous focusing of the wavepacket towards the conical intersection. In the first step an optimal laser pulse is derived by optimal control theory over the expectation values for semi-positive definite operators. In the second step chirped laser pulses are fitted to the optimal one. For the chirped laser pulses the influences of the chirp is discussed. Special emphasis is placed on the excitation of vibrations of the H₂ compound, which are considered to be important for the passage through the conical intersection.

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