TY - JOUR AU - S Bergeson AU - A Balakrishnan AU - K Baldwin AU - Thomas Lucatorto AU - J Marangos AU - T McIlrath AU - Thomas O'Brian AU - S Rolston AU - Craig Sansonetti AU - J Wen AU - N Westbrook AU - C Cheng AU - E Eyler C2 - Physical Review Letters DA - 1998-01-01 00:01:00 LA - en M1 - 80 PB - Physical Review Letters PY - 1998 TI - Measurement of the He Ground State Lamb Shift via the Two-Photon 11S-21S Transition: a new approach for testing QED at order α4 Ry and beyond ER -