Enhancing field-free molecular alignment by a polynomial phase modulation Yunxia Huang, Shuwu Xu, Yunhua Yao, Tianqing Jia, Shian Zhang and Zhenrong Sun Eur. Phys. J. D, 70 1 (2016) 9 Published online: 14 January 2016 DOI: 10.1140/epjd/e2015-60392-0