Nonadiabatic alignment of rotationally cold ${\mathrm{N}}_2$ molecules is optimally controlled by shaping femtosecond pump pulses with the feedback of degree of alignment evaluated by an ion imaging technique. The alignment is optimized by doubly peaked pulses with approximately equal intensities. A doubly peaked pulse with an appropriate interval can be regarded as a single pulse with a center trough based on the considerations from both time and frequency domains, suggesting that the effective duration of a doubly peaked pulse rather than its structure is crucial to nonadiabatic molecular alignment.

• Received 2 August 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.033603