We show that the motion of a slightly compressible fluid is near that of an incompressible fluid. That is, for a given initial velocity field, the motion of a compressible fluid with large sound speed is near to that of an idealized incompressible fluid. We consider the compressible fluid motion in Lagrangian coordinates and show that it can be defined by two functions giving the kinetic and po...

Molecular motors convert chemical energy into mechanical force and movement. Operating at energies just above those of the thermal bath, these motors experience large fluctuations, and their physical description must be necessarily stochastic. Here, motor operation is described as a biased diffusion on a potential energy surface defined by the interactions of the motor with its track and its fu...

A RCCSD(T)/cc-pVQZ potential energy surface is constructed for the HOCO radical in the ground electronic state and used to compute rotation-vibration levels of HOCO and DOCO. Two numerical strategies are employed to study in detail the wave function properties. The importance of stretch-bend coupling, such as ν4/ν5 and ν3/ν4, for the internal dynamics is demonstrated. The rotational constants c...

We determine experimentally the vector correlation among the three neutral ground state hydrogen atoms which appear in dissociation of neutral H3* molecules. The sum of the kinetic energies of the three H-atoms is fixed by selecting the energy of the H3* molecule by laser excitation in the range between 0.85 and 3.60 eV. The highly structured maps of correlation in the motion of the three atoms...

We present a novel method that appropriately handles both dynamical and static electron correlations in a balanced manner, using a perturbation theory on a spin-extended Hartree-Fock (EHF) wave function reference. While EHF is a suitable candidate for degenerate systems where static correlation is ubiquitous, it is known that most of dynamical correlation is neglected in EHF. In this work, we d...

Theoretical calculations are performed for the X2E"2 and A 2E"3 states of the cycloheptatrienyl (tropyl) radical C7H7. An important goal of these calculations is to predict and to guide the analysis of the experimentally observed A 2E"3-X 2E"2 electronic spectrum. Vibrational frequencies of the tropyl radical at the conical intersection and stationary points of its X and A state Jahn-Teller dis...

In this introductory exploration of the title theme, we treat a positron as a light nucleus and work within the quasimolecule approximation to obtain, for the first time, adiabatic potential energy curves for its scattering by the He atom. We then show that different elastic and inelastic processes that contribute to the total scattering cross section can be rationalized in molecular terms as d...

Electronic Structure Theory describes the motions of electrons in atoms or molecules. Generally this is done in the context of the Born-Oppenheimer Approximation, which says that electrons are so much lighter (and therefore faster) than nuclei that they will find their optimal distribution for any given nuclear configuration. The electronic energy at each nuclear configuration is the potential ...

for the quintet state of the O2„ 3 g − ...–O2„ 3 g − ... dimer Massimiliano Bartolomei, Estela Carmona-Novillo, Marta I. Hernández, José Campos-Martínez, and Ramón Hernandez-Lamoneda Instituto de Matemáticas y Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, 62210...