Searcharxiv⌕ Search

arXiv subjects

V. Roudnev

Publications and source records attributed to V. Roudnev.

6 recordsLinked to original sources
arXiv2019

Weakly bound LiHe$_2$ molecules in the framework of three-dimensional Faddeev equations

A method of direct solution of the Faddeev equations for the bound-state problem with zero total angular momentum is used to calculate the binding energies. The results for binding energies of He$_2$$^6$Li and He$_2$$^7$Li systems and helium atom - HeLi dimer scattering length are presented. The results show that modern potential models support two bound states in both trimers. In both cases the energy of the excited state is very close to the energy of the lowest two-body threshold.

physics.atm-clus↗
arXiv2011

Benchmark helium dimer and trimer calculations with a public few-body code

We present detailed calculations of bound and scattering states of dimers and trimers of He to produce highly accurate data and to test a non-relativistic three-body code currently in development for public distribution. For these systems, uncertainties and inaccuracies in the fundamental constants frequently used in published works can substantially exceed numerical errors. Our benchmark calculations include specific estimates of the numerical accuracy of the calculations, and also explore sensitivity to fundamental constants and their uncertainties. The use of an inexact coupling constant in the previous calculations leads to 0.08% error for the ground state energy, 0.3% error for the excited state energy and up to 0.15% error for the atom-dimer scattering length in the system of three $^4$He atoms. The corresponding errors for the unsymmetric $^{4}$He$_{2}^{3}$He system are 0.3% for the bound state energy and 0.03% for the atom-dimer scattering length.

physics.comp-ph↗
arXiv2010

Solution of three-dimensional Faddeev equations: ultracold Helium trimer calculations with a public quantum three-body code

We present an illustration of using a quantum three-body code being prepared for public release. The code is based on iterative solving of the three-dimensional Faddeev equations. The code is easy to use and allows users to perform highly-accurate calculations of quantum three-body systems. The previously known results for He$_3$ ground state are well reproduced by the code.

physics.atm-clus↗
arXiv2008

Resonance phenomena in ultracold dipole-dipole scattering

Elastic scattering resonances occurring in ultracold collisions of either bosonic or fermionic polar molecules are investigated. The Born-Oppenheimer adiabatic representation of the two-bodydynamics provides both a qualitative classification scheme and a quantitative WKB quantization condition that predicts several sequences of resonant states. It is found that the near-threshold energy dependence of ultracold collision cross sections varies significantly with the particle exchange symmetry, with bosonic systems showing much smoother energy variations than their fermionic counterparts. Resonant variations of the angular distributions in ultracold collisions are also described.

physics.atm-clus↗
arXiv2006

Unitary theory of laser Carrier-Envelope Phase effects

We consider a quantum state interacting with a short intense linearly polarized laser pulse. Using the two-dimensional time representation and Floquet picture we establish a straightforward connection between the laser carrier-envelope phase (CEP) and the wave function. This connection is revealed as a unitary transformation in the space of Floquet components. It allows any CEP effect to be interpreted as an interference between the components and to put limits on using the CEP in coherent control. A 2-level system is used to illustrate the theory. On this example we demonstrate strong intensity sensitivity of the CEP effects and predict an effect for pulses much longer than the oscillation period of the carrier.

physics.atom-ph↗