Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions

Momentum distributions of particles from nuclear break-up of fast three-body halos are calculated consistently, and applied to $^{11}$Li. The same two-body interactions between the three particles are used to calculate the ground state structure and the final state of the reaction processes. We reproduce the available momentum distributions from $^{11}$Li fragmentation, together with the size and energy of $^{11}$Li, with a neutron-core relative state containing a $p$-state admixture of 20\%-30\%. The available fragmentation data strongly suggest an $s$-state in $^{10}$Li at about 50 keV, and indicate a $p$-state around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file attached at the end of the LaTeX file). To be published in Phys. Rev.

The Effective Fragment Molecular Orbital Method for Fragments Connected by Covalent Bonds

We extend the effective fragment molecular orbital method (EFMO) into treating fragments connected by covalent bonds. The accuracy of EFMO is compared to FMO and conventional ab initio electronic structure methods for polypeptides including proteins. Errors in energy for RHF and MP2 are within 2 kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides similar to FMO but obtained two to five times faster. For proteins, the errors are also within a few kcal/mol of the FMO results. We developed both the RHF and MP2 gradient for EFMO. Compared to ab initio, the EFMO optimized structures had an RMSD of 0.40 and 0.44 {\AA} for RHF and MP2, respectively.Comment: Revised manuscrip

On calculating the Berry curvature of Bloch electrons using the KKR method

We propose and implement a particularly effective method for calculating the Berry curvature arising from adiabatic evolution of Bloch states in wave vector k space. The method exploits a unique feature of the Korringa-Kohn-Rostoker (KKR) approach to solve the Schr\"odinger or Dirac equations. Namely, it is based on the observation that in the KKR method k enters the calculation via the structure constants which depend only on the geometry of the lattice but not the crystal potential. For both the Abelian and non-Abelian Berry curvature we derive an analytic formula whose evaluation does not require any numerical differentiation with respect to k. We present explicit calculations for Al, Cu, Au, and Pt bulk crystals.Comment: 13 pages, 5 figure

Universality of three-body systems in 2D: parametrization of the bound states energies

Universal properties of mass-imbalanced three-body systems in 2D are studied using zero-range interactions in momentum space. The dependence of the three-particle binding energy on the parameters (masses and two-body energies) is highly non-trivial even in the simplest case of two identical particles and a distinct one. This dependence is parametrized for ground and excited states in terms of {\itshape supercircles} functions in the most general case of three distinguishable particles.Comment: 3 pages, 1 figure, published versio

Spectroscopic observation of resonant electric dipole-dipole interactions between cold Rydberg atoms

Resonant electric dipole-dipole interactions between cold Rydberg atoms were observed using microwave spectroscopy. Laser-cooled Rb atoms in a magneto-optical trap were optically excited to 45d Rydberg states using a pulsed laser. A microwave pulse transferred a fraction of these Rydberg atoms to the 46p state. A second microwave pulse then drove atoms in the 45d state to the 46d state, and was used as a probe of interatomic interactions. The spectral width of this two-photon probe transition was found to depend on the presence of the 46p atoms, and is due to the resonant electric dipole-dipole interaction between 45d and 46p Rydberg atoms.Comment: 5 pages, 3 figures. Accepted for publication in Phys. Rev. Lett. Titles and e-print numbers of references added to this versio

How to observe the Efimov effect

We propose to observe the Efimov effect experimentally by applying an external electric field on atomic three-body systems. We first derive the lowest order effective two-body interaction for two spin zero atoms in the field. Then we solve the three-body problem and search for the extreme spatially extended Efimov states. We use helium trimers as an illustrative numerical example and estimate the necessary field strength to be less than 2.7 V/angstrom.Comment: 4 pages, 2 postscript figures, psfig.sty, revte