arXiv subjects

Marko T. Cvitas

Publications and source records attributed to Marko T. Cvitas.

7 recordsLinked to original sources

arXiv2007

Interactions and dynamics in Li + Li_2 ultracold collisions

A potential energy surface for the lowest quartet electronic state of lithium trimer is developed and used to study spin-polarized Li + Li_2 collisions at ultralow kinetic energies. The potential energy surface allows barrierless atom exchange reactions. Elastic and inelastic cross sections are calculated for collisions involving a variety of rovibrational states of Li_2. Inelastic collisions are responsible for trap loss in molecule production experiments. Isotope effects and the sensitivity of the results to details of the potential energy surface are investigated. It is found that for vibrationally excited states the cross sections are only quite weakly dependent on details of the potential energy surface.

physics.chem-ph↗

arXiv2005

Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-diatom C_8 coefficients. The resulting expressions are applied to dispersion coefficients for Li + Li_2 (triplet) and recommendations are made for the best way to obtain global triatomic potentials that dissociate correctly both to three separated atoms and to an atom and a diatomic molecule.

physics.atm-clus↗

arXiv2005

Ultracold collisions involving heteronuclear alkali metal dimers

We have carried out the first quantum dynamics calculations on ultracold atom-diatom collisions in isotopic mixtures. The systems studied are spin-polarized 7Li + 6Li7Li, 7Li + 6Li2, 6Li + 6Li7Li and 6Li + 7Li2. Reactive scattering can occur for the first two systems even when the molecules are in their ground rovibrational states, but is slower than vibrational relaxation in homonuclear systems. Implications for sympathetic cooling of heteronuclear molecules are discussed.

cond-mat.other↗

arXiv2004

Ultracold Li + Li_2 collisions: bosonic and fermionic cases

We have carried out quantum dynamical calculations of vibrational quenching in Li + Li_2 collisions for both bosonic 7Li and fermionic 6Li. These are the first ever such calculations involving fermionic atoms. We find that for the low initial vibrational states considered here (v less than or equal to 3), the quenching rates are not suppressed for fermionic atoms. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states.

cond-mat.soft↗

arXiv2003

Vibrations of a chain of Xe atoms in a groove of carbon nanotube bundle

We present a lattice dynamics study of the vibrations of a linear chain of Xe adsorbates in groove positions of a bundle of carbon nanotubes. The characteristic phonon frequencies are calculated and the adsorbate polarization vectors discussed. Comparison of the present results with the ones previously published shows that the adsorbate vibrations cannot be treated as completely decoupled from the vibrations of carbon nanotubes and that a significant hybridization between the adsorbate and the tube modes occurs for phonons of large wavelengths.

cond-mat.stat-mech↗

arXiv2002

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.

cond-mat.soft↗

arXiv2002

Quantum Dynamics of Ultracold Na + Na_2 collisions

Ultracold collisions between spin-polarized Na atoms and vibrationally excited Na_2 molecules are investigated theoretically, using both an inelastic formalism (neglecting atom exchange channels) and a reactive formalism (including atom exchange). Calculations are carried out on both pairwise additive and non-additive potential energy surfaces for the quartet electronic state. In both inelastic and reactive calculations, the Wigner threshold laws are followed for energies below 10^{-6} K. It is found that vibrational relaxation processes dominate elastic processes for temperatures below 10^{-3} - 10^{-4} K. For temperatures below 10^{-5} K, the rate coefficients for vibrational relaxation (v = 1 -> 0) from the full calculation are 4.8 x 10^{-11} and 5.2 x 10^{-10} cm^3 s^-1 for the additive and non-additive potentials respectively.

cond-mat.soft↗