Shaping coherent excitation of atoms and molecules by a train of   ultrashort laser pulses
  We propose a mechanism to produce a superposition of atomic and molecular states by a train of ultrashort laser pulses combined with weak control fields. By adjusting the repetition rate of the pump pulses and the intensity of the coupling laser, one can suppress a transition while simultaneously enhancing the desired transitions. As an example, various superpositions of vibrational states of the $K_2$ molecule are shown. 
Anahit Gogyan, Stephane Guerin and Yuri Malakyan
physics.atom-ph physics.optics quant-ph