Attosecond light pulses to reveal the time-dependent rovibrational   motion of the correlated electron pair in helium
  We illustrate how attosecond light pulses can be used to directly mapping out the time-dependence of the correlated motion of two excited atomic electrons, discuss how the two-electron correlations manifest themselves in realistic attosecond measurements, and propose the following for experimental exploration:   (a) The single ionization signals which directly reveal bending-vibrational motion of the correlated electron pair,   (b) and also its rotational motion.   (c) The double ionization signals which directly reveal the two-electron density in momentum space. To facilitate the description of the above points, use is made of simple wave packets of doubly-excited states of helium. 
Toru Morishita, Shinichi Watanabe, and C. D. Lin