We give a general reduction scheme for the study of the quantum propagator of molecular Schrr odinger operators with smooth potentials. This reduction is made up to innnitely (resp. exponentially) small error terms with respect to the inverse square root of the mass of the nuclei, depending on the C 1 (resp. analytic) smoothness of the interactions. Then we apply this result to the case when an...

We study periodic well-to-well flopping of rubidium atoms in one-dimensional grey optical lattices using a nondestructive, real-time measurement technique and quantum Monte Carlo wavefunction simulations. The observed flopping rates as well as flopping rates extracted from exact band structure calculations can largely be reproduced using adiabatic models that employ the Born–Oppenheimer approxi...

In this work we develop tools that enable the study of non-adiabatic effects with variational and diffusion Monte Carlo methods. We introduce a highly accurate wave function ansatz for electronion systems that can involve a combination of both fixed and quantum ions. We explicitly calculate the ground state energies of H2, LiH, H2O and FHF − using fixed-node quantum Monte Carlo with wave functi...

In the Born-Oppenheimer approximation, the electronic wave function is typically real-valued and hence the electronic flux density (current density) seems to vanish. This is unfortunate for chemistry, because it precludes the possibility to monitor the electronic motion associated with the nuclear motion during chemical rearrangements from a Born-Oppenheimer simulation of the process. We study ...