Optimal molecular alignment and orientation through rotational ladder climbing

J. Salomon¹, C. M. Dion², and G. Turinici^3,4

¹Laboratoire Jacques-Louis Lions, Université Pierre & Marie Curie, Boîte courrier 187, 75252 Paris Cedex 05, France
²Department of Physics, Umeå University, SE-901 87 Umeå, Sweden
³INRIA Rocquencourt, B.P. 105, 78153 Le Chesnay Cedex, France
⁴CERMICS-ENPC, Champs-sur-Marne, 77455 Marne-la-Vallée Cedex, France

We study the control by electromagnetic fields of molecular alignment and orientation, in a linear, rigid rotor model. With the help of a monotonically convergent algorithm, we find that the optimal field is in the microwave part of the spectrum and acts by resonantly exciting the rotation of the molecule progressively from the ground state, i.e., by rotational ladder climbing. This mechanism is present not only when maximizing orientation or alignment, but also when using prescribed target states that simultaneously optimize the efficiency of orientation/alignment and its duration. The extension of the optimization method to consider a finite rotational temperature is also presented.

This article has been published in The Journal of Chemical Physics 123, 144310 (2005).

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