Development of a program for the calculation of attosecond time-resolved photoelectron spectra and its application to photo-induced electron transfer reactions

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Time-resolved photoelectron spectroscopy is useful for probing the dynamics of a molecule that undergoes chemical reactions. To calculate the probability of intense-field-induced ionization or photoelectron spectrum of a time-evolving electronic state as a function of internuclear distances R, we combined wave packet propagation methods for bound electronic state dynamics, such as the time-dependent (TD) adiabatic state approach or the multiconfigurational TD Hartree-Fock method, with the intense-field many-body S-matrix theory. Our new approach was applied to H^+_2. The calculated ionization probability as a function of R is in good agreement with the exact one obtained by an accurate grid point method. Ionization of H: is greatly enhanced at a critical internuclear distance which is much longer than the equilibrium one (known as enhanced ionization). The angular distribution of the photoelectron momentum experimentally observed is reproduced as well. The distribution of the momentum perpendicular to the laser polarization direction has a sharp peak near zero momentum. The "cusp-like" distribution is due to excited state dynamics leading to ionization. We then calculated the photoelectron angular distribution of above-threshold ionization of H_2. We have also calculated the ionization probabilities of polyatomic molecules such as ethanol and water molecule to show that intramolecular electron dynamics is the key to understand the mechanism of enhanced ionization.