Direct imaging of direction-controlled molecular rotational wave packets created by a polarization-skewed double-pulse

摘要： High‐precision, time‐resolved Coulomb explosion imaging of rotational wave packets in nitrogen molecules created with a pair of time‐delayed, polarization‐skewed femtosecond laser pulses is presented, providing insight into creation process and dynamics of direction‐controlled wave packet. To initiate unidirectional rotation, the interval of the double‐pulse was set so that the second, polarization‐tilted pulse hit the molecules at the time when molecules were aligned or antialigned along the polarization vector of the first pulse. During the revival period of the rotational wave packet, pulse intervals around both the full and half revival times were used. The observed molecular wave packet movies clearly show signatures of quantum rotation such as angular localization (alignment), dispersion, and revival phenomena during the unidirectional motion. The patterns are quite different depending on the pulse interval even when angular distribution at the second pulse irradiation is similar. The observed interval‐dependence of the dynamics was analyzed on the basis of the real‐time images, with an aid of numerical simulations, and the creation process of the packets were discussed. We show the observed image patterns can be essentially rationalized in terms of rotational period and alignment parameter. Because the double‐pulse scheme is the most fundamental in the creation of direction‐controlled rotational wave packets, this study will lead to more sophisticated control and characterization of directional molecular motions.