Sustained elimination of molecular alignment dephasing via coherent control with phase-modulated pulse trains

Suppressing molecular alignment dephasing is of significant practical value for applications involving non-rigid rotors. In this work, we propose a strategy that employs a train of time-delayed, phase-modulated laser pulses to achieve elimination of alignment dephasing over an extended temporal window. Our findings demonstrate that for molecules with short rotational periods, such as CO or N 2 used in this study, dephasing can be completely eliminated for at least a dozen revival periods, thereby restoring alignment approaching the rigid-rotor limit. For molecules exhibiting longer revival periods, however, the effectiveness of this approach is somewhat diminished. While complete dephasing elimination is not achieved in such cases, the method remains sufficiently effective for most practical applications. We also qualitatively analyze the underlying reasons for the reduced performance in molecules with longer rotational periods.