With the three-dimensional (3D) classical ensemble method, we theoretically investigate the recollision dynamics in strong-field nonsequential double ionization (NSDI) of Ar by counter-rotating two-color circularly polarized laser fields. With the analysis of the NSDI trajectories, we find that not only multiple-recollision but also single-recollision processes occur in the double ionization events. Furthermore, the multiple-recollision and single-recollision processes both undergo the recollision-induced excitation with subsequent ionization (RESI) and recollision-induced ionization (RII). The angle between the momentum and the force of the laser field at the recollision moment can affect the times of the recollision.

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Abstract. With the rapid development of MOOCs at home and abroad, the dropout low through rate results in unsatisfactory teaching effects problem that has gradually become the focus of study. In order to improve the MOOCs platform effect, using multiple concentric learning theory designs MOOCs multi angle movable concentric learning model, using VP-model constructs the node to expand the capacity of the channel, making the learning platform channel can accommodate multi angle learning content, and using the modulation and demodulation and orthogonal transformation can get the multi channel acceptance model. Finally, through the analysis of the information transmission delay characteristic curve, we found that the virtual platform can be multi channel communication effectively by user end learning content to accept the curve, the method can effectively improve the efficiency of learning.