Femtosecond energy- and angle-resolved photoelectron spectra

We present energy- and angle-resolved photoelectron spectra for femtosecond pump-probe ionization of wavepackets in the (1)Sigma(u)(+) double-minimum state for aligned Na(2). These results illustrate that a robust description of the underlying photoionization amplitudes can significantly enhance the utility of photoelectron spectroscopy as a probe of wavepacket motion and of the evolution of electronic structure, particularly in cases of avoided crossings and motion over large distances. The angular dependence of these photoelectron spectra provide insightful fingerprints of vibrational wavepacket dynamics and can be a useful real-time probe of molecular rotation. (C) 1999 Elsevier Science B.V. All rights reserved.