Molecular frame photoelectron angular distributions for H2 ionization by single and trains of attosecond XUV laser pulses

The delayed autoionization of H₂ doubly excited states into channels of different inversion symmetry gerade and ungerade is investigated by using pulses of attosecond duration (isolated or packed in trains), linearly polarized along the molecular axis. It has been shown in previous work, by using XUV laser pulses with durations of 4 fs or longer, that the molecular frame photoelectron angular distributions (MFPAD) associated with the dissociative channel H⁺ + H(n?) are not symmetric with respect to the inversion center of the molecule. In contrast, the MFPADs become symmetric for shorter fs pulses. Here we show that, although this is still the case for pulses of attosecond duration, the combination of two of these pulses with a controlled time delay may still lead to asymmetric MFPADs. From the analysis of the time evolution of the calculated MFPADs, we propose a way to elucidate autoionization lifetimes of molecular resonant states. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2462–2471, 2010