Resonance enhanced electron impact excitation of Cu-like gadolinium Shuang Li, Ran Si, Chun yu Zhang, Xue Ling Guo, Zhan Bin Chen, Kai Wang, Chong Yang Chen and Jun Yan Eur. Phys. J. D, 71 6 (2017) 156 Published online: 15 June 2017 DOI: 10.1140/epjd/e2017-70779-4