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The potential energy curves (PECs) of the X(2)Π and A(2)Π electronic states of the SO(+) ion are calculated using the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction (MRCI) approach for internuclear separations from 0.08 to 1.06 nm. The spin-orbit coupling effect on the spectroscopic parameters is included using the Breit-Pauli operator. To improve the quality of PECs and spin-orbit coupling constant (A(0)), core-valence correlation and scalar relativistic corrections are included. To obtain more reliable results, the PECs obtained by the MRCI calculations are corrected for size-extensivity errors by means of the Davidson modification (MRCI+Q). At the MRCI+Q/aug-cc-pV5Z+CV+DK level, the A(0) values of the SO(+)(X(2)Π(1/2, 3/2)) and SO(+)(A(2)Π(1/2, 3/2)) are 362.13 and 58.16 cm(-1) when the aug-cc-pCVTZ basis set is used to calculate the spin-orbit coupling splitting, and the A(0) of the SO(+)(X(2)Π(1/2, 3/2)) and SO(+)(A(2)Π(1/2, 3/2)) are 344.36 and 52.90 cm(-1) when the aug-cc-pVTZ basis set is used to calculate the spin-orbit coupling splitting. The conclusion is drawn that the core-valence correlations correction makes the A(0) slightly larger. The spectroscopic results are obtained and compared with those reported in the literature. Excellent agreement exists between the present results and the measurements. The vibrational manifolds are calculated, and those of the first 30 vibrational states are reported for the J = 0 case. Comparison with the measurements shows that the present vibrational manifolds are both reliable and accurate.

The potential energy curves (PECs) of ten Ω states (X2Π1 / 2,3 / 2, a4Π1 / 2,1 / 2,3 / 2,5 / 2, B2Π1 / 2,3 / 2 and H2Π1 / 2,3 / 2) generated from four Λ-S states (X2Π, a4Π, B2Π and H2Π) of the NS radical are studied in detail for the first time using an ab initio quantum chemical method. All the PEC calculations are performed for internuclear separations from 0.10 to 1.11 nm by the complete active space self-consistent field method followed by the internally contracted multireference configuration interaction approach with the Davidson modifications (MRCI + Q). The spin-orbit coupling (SO) effect is accounted for by the Breit- Pauli Hamiltonian. To discuss the effect on the energy splitting by the core-electron correlations, two all-electron basis sets, cc-pCVTZ and cc-pVTZ, are used for the SO coupling calculations. To improve the quality of the PECs, core-valence correlation and relativistic corrections are included. Core-valence correlation corrections are included with a cc-pCVTZ basis set. Relativistic correction calculations are carried out using the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. The spectroscopic parameters of four Λ-S states and ten Ω states are calculated. Excellent agreement is found between the present results and the measurements. Using the PECs obtained by the MRCI + Q/AV5Z + CV + DK + SO calculations, the G(υ), B υ and D υ are calculated for each vibrational state of each Ω state, and those of the first 30 vibrational states are reported for the X2Π1 / 2, X2Π3 / 2, B2Π1 / 2 and B2Π3 / 2 states of the 14N32S radical. The spectroscopic parameters of four Ω states of the a4Π and the G(υ), B υ and D υ of the X2Π1 / 2, X2Π3 / 2, B2Π1 / 2 and B2Π3 / 2 states reported here are expected to be reliable predicted results.

The potential energy curves (PECs) of the X 1 Σ + , a 3 Σ + , A 1 Π and C 1 Σ − electronic states of the SiO molecule are studied using an ab initio quantum chemical method. The calculations have been made employing the complete active space self-consistent field (CASSCF) method, which is followed by the valence internally contracted multireference configuration interaction (MRCI) approach in combination with several correlation-consistent basis sets. The effect on the PECs by the core-valence correlation and relativistic corrections is included. The way to consider the relativistic correction is to use the third-order Douglas–Kroll Hamiltonian approximation. The core-valence correlation correction is carried out with the cc-pCVQZ basis set, and the relativistic correction is performed at the level of the cc-pVQZ basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification (MRCI + Q). The PECs of these electronic states are extrapolated to the complete basis set limit by the total-energy extrapolation scheme. Employing these PECs, the spectroscopic parameters are calculated and compared with those reported in the literature. With these PECs determined by the MRCI + Q/CV + DK + 56 calculations, by solving the radial Schrodinger equation of nuclear motion, 110 vibrational states for the X 1 Σ + , 69 for the a 3 Σ + , 54 for the A 1 Π and 67 for the C 1 Σ − electronic state are predicted when the rotational quantum number J equals zero. The vibrational manifolds of the first 20 vibrational states are reported and compared with the available RKR data for each electronic state. On the whole, as expected, the most accurate spectroscopic parameters and molecular constants of the SiO molecule are obtained by the MRCI + Q/CV + DK + 56 calculations. And the present molecular constants of the a 3 Σ + , C 1 Σ − and A 1 Π electronic states determined by the MRCI + Q/CV + DK + 56 calculations should be good prediction for future laboratory experiment.

Scattering properties of ultracold atoms are sensitive to the interatomic potential. Based on the accurate triplet least-bound state energy, we calculate the triplet s-wave scattering length for 23Na?40K. The scattering length is ?814.1+29?31.3a0 with a0 being the Bohr radius. By using the mass scaling method, those scattering lengths are also obtained for 23Na?41K and 23Na?39K. The degenerate internal state approximation is used to estimate the scattering data of atoms colliding in different spin states.

The s-wave scattering lengths are obtained for all stable isotope combinations of Ca atoms and those values are very sensitive to small changes of the reduced mass. These results rely on a recent measurement of the 40Ca–40Ca scattering length in a Bose condensate of 40Ca and making small corrections to a Born–Oppenheimer potential that reproduces all known spectroscopic data. We find that the 42Ca isotope has a scattering length of 417.5a0 and, thus, can be Bose condensed. The large interisotope scattering length between 43Ca and 42Ca indicates that sympathetic cooling of 43Ca by 42Ca atoms will be effective, and 43Ca–42Ca can also be used to study isotopic Bose–Fermi mixtures. We also predict a d-wave shape resonance for collisions of fermionic 43Ca atoms in different spin components.

We investigate the elastic scattering properties of strontium atoms at ultracold temperatures. The scattering parameters, such as s-wave scattering lengths, effective ranges and p-wave scattering lengths, are calculated for all stable isotope combinations of Sr atoms by the quantal method and semiclassical method, respectively. Good agreements are obtained. The scattering parameters are very sensitive to small changes of the reduced mass. Due to the repulsive interisotope and intraisotope s-wave scattering length and large elastic cross sections, 84Sr—86Sr mixture is a good candidate to realize Bose—Bose quantum degenerate atomic gases.

Taking into consideration the contributions of the geometric shielding effect in the molecule, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. The total cross sections for electron scattering by eight larger polyatomic molecules (C6H6, C6F6, C6H12, C6H14, C8H16, C8H18, C6F14 and C8F18) are calculated using the new additivity rule at the Hartree–Fock level for impact energies ranging from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is attained above 100 eV or so. The new results for C6F14 and C8F18 are also presented although no experimental and theoretical data are available for comparison in the present energy region. In these calculations, the atoms are represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.