113 research outputs found
Adiabatic hyperspherical study of triatomic helium systems
The 4He3 system is studied using the adiabatic hyperspherical representation.
We adopt the current state-of-the-art helium interaction potential including
retardation and the nonadditive three-body term, to calculate all low-energy
properties of the triatomic 4He system. The bound state energies of the 4He
trimer are computed as well as the 4He+4He2 elastic scattering cross sections,
the three-body recombination and collision induced dissociation rates at finite
temperatures. We also treat the system that consists of two 4He and one 3He
atoms, and compute the spectrum of the isotopic trimer 4He2 3He, the 3He+4He2
elastic scattering cross sections, the rates for three-body recombination and
the collision induced dissociation rate at finite temperatures. The effects of
retardation and the nonadditive three-body term are investigated. Retardation
is found to be significant in some cases, while the three-body term plays only
a minor role for these systems.Comment: 24 pages 6 figures Submitted to Physical Review
Time-dependent Density Functional Study on Excited Hydrogen Atom Formation via Non-resonant Electron Capture by a Proton from Refractory Metal Surfaces
Study on Excited State Distribution of Reflected Hydrogen Atoms at Metal First Walls by the Quantum-classical Mixed Model
The helium trimer with soft-core potentials
The helium trimer is studied using two- and three-body soft-core potentials.
Realistic helium-helium potentials present an extremely strong short-range
repulsion and support a single, very shallow, bound state. The description of
systems with more than two helium atoms is difficult due to the very large
cancellation between kinetic and potential energy. We analyze the possibility
of describing the three helium system in the ultracold regime using a gaussian
representation of a widely used realistic potential, the LM2M2 interaction.
However, in order to describe correctly the trimer ground state a three-body
force has to be added to the gaussian interaction. With this potential model
the two bound states of the trimer and the low energy scattering helium-dimer
phase shifts obtained with the LM2M2 potential are well reproduced.Comment: 15 pages, 3 figures, submitted to Few-Body System
Effective interactions, Fermi-Bose duality, and ground states of ultracold atomic vapors in tight de Broglie waveguides
Derivation of effective zero-range one-dimensional (1D) interactions between
atoms in tight waveguides is reviewed, as is the Fermi-Bose mapping method for
determination of exact and strongly-correlated states of ultracold bosonic and
fermionic atomic vapors in such waveguides, including spin degrees of freedom.
Odd-wave 1D interactions derived from 3D p-wave scattering are included as well
as the usual even-wave interactions derived from 3D s-wave scattering, with
emphasis on the role of 3D Feshbach resonances for selectively enhancing s-wave
or p-wave interactions. A duality between 1D fermions and bosons with
zero-range interactions suggested by Cheon and Shigehara is shown to hold for
the effective 1D dynamics of a spinor Fermi gas with both even and odd-wave
interactions and that of a spinor Bose gas with even and odd-wave interactions,
with even(odd)-wave Bose coupling constants inversely related to odd(even)-wave
Fermi coupling constants. Some recent applications of Fermi-Bose mapping to
determination of many-body ground states of Bose gases and of both magnetically
trapped, spin-aligned and optically trapped, spin-free Fermi gases are
described, and a new generalized Fermi-Bose mapping is used to determine the
phase diagram of ground-state total spin of the spinor Fermi gas as a function
of the even and odd-wave coupling constants.Comment: 16 pages, 3 figures. Submitted to Optics Communications for special
issue "Degenerate Quantum Gases
Features of Idebenone and Related Short-Chain Quinones that Rescue ATP Levels under Conditions of Impaired Mitochondrial Complex I
Short-chain quinones have been investigated as therapeutic molecules due to their ability to modulate cellular redox reactions, mitochondrial electron transfer and oxidative stress, which are pathologically altered in many mitochondrial and neuromuscular disorders. Recently, we and others described that certain short-chain quinones are able to bypass a deficiency in complex I by shuttling electrons directly from the cytoplasm to complex III of the mitochondrial respiratory chain to produce ATP. Although this energy rescue activity is highly interesting for the therapy of disorders associated with complex I dysfunction, no structure-activity-relationship has been reported for short-chain quinones so far. Using a panel of 70 quinones, we observed that the capacity for this cellular energy rescue as well as their effect on lipid peroxidation was influenced more by the physicochemical properties (in particular logD) of the whole molecule than the quinone moiety itself. Thus, the observed correlations allow us to explain the differential biological activities and therapeutic potential of short-chain quinones for the therapy of disorders associated with mitochondrial complex I dysfunction and/or oxidative stress
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
Universality in the Three-Body Problem for 4He Atoms
The two-body scattering length a for 4He atoms is much larger than their
effective range r_s. As a consequence, low-energy few-body observables have
universal characteristics that are independent of the interaction potential.
Universality implies that, up to corrections suppressed by r_s/a, all
low-energy three-body observables are determined by a and a three-body
parameter \Lambda_*. We give simple expressions in terms of a and \Lambda_* for
the trimer binding energy equation, the atom-dimer scattering phase shifts, and
the rate for three-body recombination at threshold. We determine \Lambda_* for
several 4He potentials from the calculated binding energy of the excited state
of the trimer and use it to obtain the universality predictions for the other
low-energy observables. We also use the calculated values for one potential to
estimate the effective range corrections for the other potentials.Comment: 23 pages, revtex4, 6 ps figures, references added, universal
expressions update
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