10 research outputs found
Three-body interactions in colloidal systems
We present the first direct measurement of three-body interactions in a
colloidal system comprised of three charged colloidal particles. Two of the
particles have been confined by means of a scanned laser tweezers to a
line-shaped optical trap where they diffused due to thermal fluctuations. Upon
the approach of a third particle, attractive three-body interactions have been
observed. The results are in qualitative agreement with additionally performed
nonlinear Poissson-Boltzmann calculations, which also allow us to investigate
the microionic density distributions in the neighborhood of the interacting
colloidal particles
Three-body non-additive forces between spin-polarized alkali atoms
Three-body non-additive forces in systems of three spin-polarized alkali
atoms (Li, Na, K, Rb and Cs) are investigated using high-level ab initio
calculations. The non-additive forces are found to be large, especially near
the equilateral equilibrium geometries. For Li, they increase the three-atom
potential well depth by a factor of 4 and reduce the equilibrium interatomic
distance by 0.9 A. The non-additive forces originate principally from chemical
bonding arising from sp mixing effects.Comment: 4 pages, 3 figures (in 5 files
Efimov physics beyond universality
We provide an exact solution of the Efimov spectrum in ultracold gases within
the standard two-channel model for Feshbach resonances. It is shown that the
finite range in the Feshbach coupling makes the introduction of an adjustable
three-body parameter obsolete. The solution explains the empirical relation
between the scattering length a_- where the first Efimov state appears at the
atom threshold and the van der Waals length l_vdw for open channel dominated
resonances. There is a continuous crossover to the closed channel dominated
limit, where the scale in the energy level diagram as a function of the inverse
scattering length 1/a is set by the intrinsic length r* associated with the
Feshbach coupling. Our results provide a number of predictions for
non-universal ratios between energies and scattering lengths that can be tested
in future experiments.Comment: 6 pages, 4 figures; final versio