  We explore a new fashion, named energy-resolved population image (EPI), to
represent on an equal footing the temporary electronic transition and nuclear
motion during laser-molecular interaction. By using the EPI we have intuitively
demonstrated the population transfer in vibrational H$_2^+$ exposed to extreme
ultraviolet pulses, revealing the energy sharing rule for the correlated
electron and nuclei. We further show that the EPI can be extended to uncover
the origins of the distinct energy sharing mechanisms in multi-photon and
tunneling regimes. The present study has clarified a long-standing issue about
the dissociative ionization of H$_2^+$ and paves the way to identify
instantaneous molecular dynamics in strong fields.
