Double-pulse measurements of laser-induced alignment of molecules

The nonlinear interaction of molecules with intense laser fields is a potential method of preparing states with very high degrees of alignment. The physical rotation of molecules can be confirmed using two pulses of orthogonal polarization and by observing the behaviour of the lowest fragmentation channels. New results show that this dynamic alignment is molecule specific. In the case of , virtually all molecules are depleted by the pump pulse, but we see no evidence for rotation of , in agreement with recent systematic studies of angular distributions. Further analysis indicates that the ubiquity of laser-induced alignment has thus far been overestimated.