  We identify that both the dynamic core polarization and dynamic orbital
deformation are important in the orientation-dependent high-harmonic generation
of CO molecules subjected to intense few cycle laser fields. These polarization
dynamics allow for the observation of strong orientation effects and dynamic
minimum in the harmonic spectra. The generated attosecond pulses can be greatly
affected by these multielectron effects. This work sheds light on future
development of dynamic orbital imaging on attosecond time scale.
