Interaction between the ultrashort pulse and two-level medium beyond the rotating wave approximationLong-Zhao Lu, Da-Qing Wen, Shao-Ji Jiang and Xiang-Yang YuEur. Phys. J. D, 70 9 (2016) 184DOI: https://doi.org/10.1140/epjd/e2016-70038-4