Total differential cross sections for Ar–CH4 from an ab initio potential

Total differential cross sections for the Ar–CH4 scattering complex at ECM=90.1 meV were obtained from converged close-coupling calculations based on a recent ab initio potential computed by symmetry-adapted perturbation theory (SAPT). Agreement with experiment is good, which demonstrates the accuracy of the SAPT potential

Ultracold collisions of oxygen molecules

Collision cross sections and rate constants between two ground- state oxygen molecules are investigated theoretically at translational energies below $\sim 1$K and in zero magnetic field. We present calculations for elastic and spin- changing inelastic collision rates for different isotopic combinations of oxygen atoms as a prelude to understanding their collisional stability in ultracold magnetic traps. A numerical analysis has been made in the framework of a rigid- rotor model that accounts fully for the singlet, triplet, and quintet potential energy surfaces in this system. The results offer insights into the effectiveness of evaporative cooling and the properties of molecular Bose- Einstein condensates, as well as estimates of collisional lifetimes in magnetic traps. Specifically, $^{17}O_{2}$ looks like a good candidate for ultracold studies, while $^{16}O_{2}$ is unlikely to survive evaporative cooling. Since $^{17}O_{2}$ is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.Comment: 15 pages, 9 figure

Frequency-dependent polarizabilities and van der Waals coefficients of half-open-shell systems in the time-dependent coupled Hartree-Fock approximation

In this paper we present a derivation of time-dependent coupled Hartree-Fock (TDCHF) theory for the case of half-open shells. With this method frequency-dependent polarizabilities are calculated for the hydrogen and nitrogen atom, as well as for the diatomics CN, NH, and OH. van der Waals coefficients of the half-open-shell systems with the H atom and the H molecule are computed. Other dispersion coefficients for dimers consisting of these monomers are available upon request

Intramolecular bond length dependence of the anisotropic dispersion coefficients for H2-rare gas interactions

Effective states arising from variational perturbation calculations in a full configuration interaction basis are used to calculate dynamic multipole polarizabilities for H at seven different bond lengths. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic C , C, and C dispersion coefficients for H-X (X=He, Ne, Ar, Kr, Xe) interactions. The results are generally in good agreement with previous semiempirical estimates where available

Intramolecular bond length dependence of the anisotropic dispersion coefficients for interactions of rare gas atoms with N2, CO, Cl2, HCl and HBr

Ab initio many body perturbation theory is used to calculate the imaginary frequency multipole polarizabilities of N, Cl, CO, HCl and HBr as a function of bond length. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic dispersion and induction coefficients through R for AB-X (AB = N, Cl, CO, HCl, HBr and X = He, Ne, Ar, Kr, Xe) interactions

Ab initio dispersion coefficients for interactions involving rare-gas atoms

Calculations of the dynamic dipole, quadrupole, and octopole polarizabilities of Ne, Ar, Kr, and Xe are carried out using both time-dependent coupled Hartree-Fock and many-body perturbation theory methods. Dispersion coefficients are calculated for interactions involving these species. The dynamic polarizabilities are combined with previously published dynamic polarizabilities of H, He, H, N, HF, and CO to obtain dispersion coefficients for the interactions involving one of these species and one of Ne, Ar, Kr, or Xe. The dipole-dipole dispersion coefficients agree quite well with the best available semiempirical estimates. The isotropic higher multipole coefficients are in reasonable agreement with previous semi-empirical estimates where available, and the anisotropic ones are, in most cases, the first reliable ones to appear in the literature. Nonadditive three-body dispersion coefficients for the Ne, Ar, Kr, and Xe interactions are also calculated