Quantized form factor shift in the presence of free electron laser radiation F. Fratini, L. Safari, A. G. Hayrapetyan, K. Jänkälä, P. Amaro and J. P. Santos EPL, 107 1 (2014) 13002 Published online: 08 July 2014 DOI: 10.1209/0295-5075/107/13002