TY - JOUR KW - pfc AU - Hongcheng Ni AU - Shaohao Chen AU - Camilo Ruiz AU - Andreas Becker BT - Journal of Physics B: Atomic, Molecular and Optical Physics DA - 2011-08 DO - 10.1088/0953-4075/44/17/175601 PY - 2011 EP - 175601 T2 - Journal of Physics B: Atomic, Molecular and Optical Physics TI - Selection rules in the few-photon double ionization of the helium atom VL - 44 ER -