Energy- and angle-resolved pump–probe femtosecond photoelectron spectroscopy: Molecular rotation

We have incorporated a classical treatment of molecular rotation into our formulation of energy- and angle-resolved pump–probe photoelectron spectroscopy. This classical treatment provides a useful approach to extracting the photoelectron signal primarily associated with vibrational dynamics in cases where rotational motion is slow and the coupling between rotational and vibrational motion is weak. We illustrate its applicability with pump–probe photoelectron spectra for wave packets on the ^1Σ^+_u double-minimum state of Na_2.