The resonant Auger decay of water molecules is investigated. Here, the excitation process, the motion of the nuclei, and the decay of the resonantly excited state take place on the same (femtosecond) time scale. Therefore, a multistep picture is not suitable. Instead, the nuclear wave packet at each instant of time is a result of several competing and interfering contributions. The resonant Auger decay of water is simulated and its dynamics is studied in detail. An analysis of the final vibrational distribution is given. The multiconfiguration time-dependent Hartree method is used to study the intricate multidimensional dynamics. The potential energy surfaces have been calculated using a multireference configuration interaction method.

The gas-phase photoelectron spectrum of water in the 12-20 eV energy range is simulated. The potential energy surfaces (PESs) of the three cationic states involved show several degeneracies. The ground state (X(2)B(1)) and the first excited state (A(2)A(1)) are degenerate components of a (2)Pi(u) state in linear geometry leading to Renner-Teller coupling while the PESs of the A state and the second excited state (B(2)B(2)) exhibit a conical intersection. Thus, an adiabatic approach that relies on sufficiently separated surfaces deems inappropriate. However, an orthogonal transformation of the electronic states removes the diverging matrix elements in the kinetic energy. These diabatic states permit a correct treatment of the nuclear dynamics near a conical intersection as well as in the Renner-Teller zone. The quantum mechanical equations of motion of the nuclei are solved using the multiconfiguration time-dependent Hartree (MCTDH) method. Quantum chemical calculations for the cationic states had been performed before, using a multireference configuration interaction method.

We present a theoretical investigation of the resonant Auger effect in gas-phase water. As in our earlier work, the simulation of nuclear dynamics is treated in a one-step picture, because excitation and decay events cannot be disentangled. Extending this framework, we now account for the vibronic coupling in the cationic final states arising from degeneracies in their potential energy surfaces (PESs). A diabatization of the cationic states permits a correct treatment of non Born-Oppenheimer dynamics leading to a significantly better agreement with experimental results. Moreover, we arrive at a more balanced understanding of the various spectral features that can be attributed to nuclear motion in the core-excited state or to vibronic coupling effects. The nuclear equations of motion have been solved using the multiconfiguration time-dependent Hartree (MCTDH) method. The cationic PESs were recalculated using the coupled electron pair approach (CEPA) whereas previously a multireference configuration interaction method had been employed.

Linear transport through a single-walled carbon nanotube ring (CNR), pierced by a magnetic field and capacitively coupled to a gate voltage source, is investigated starting from a model of interacting $p_z$-electrons. The dc-conductance, calculated in the limit of weak tunneling between the ring and the leads, displays a periodic resonance pattern determined by the interplay between Coulomb interactions and quantum interference phenomena. Coulomb blockade effects are manifested in the absence of resonances for any applied flux in some gate voltage regions; the periodicity as a function of the applied flux can be smaller or larger than a flux quantum depending on the nanotube band mismatch