Elastic collision between S and D atoms at low temperatures and accurate analytic interaction potential and molecular constants of the SD(X2Π) radical

The equilibrium internuclear separations, harmonic frequencies and interaction potentials have been calculated by employing the CCSDT theory in combination with the series of the correlation- consistent basis sets, cc-pVnZ and aug-cc-pVnZ n=2, 3, 4, 5, of Dunning and co-workers. The potential energy curves are all fitted to the Murrell-Sorbie functions, which are used to determine the spectroscopic parameters. At the CCSDT/aug-cc-pV5Z level of theory, the values of D0, De, Re, ωe, αe, B0 are 3.65730 eV, 3.77669 eV, 0.13424 cm1, 1938.372 cm1, 0.09919 cm1, 4.88585 cm1 and 4.8872 cm1, respectively, which conform almost perfectly with the available measurements. With the analytic interaction potential obtained at the CCSDT/aug-cc-pV5Z level of theory, a total of 23 vibrational states has been predicted for the first time when the rotational quantum number J is set to equal zero J=0 by solving the radial Schrdinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced from the SDX2Π potential when J=0 The total and various partial-wave cross sections are calculated for the elastic collisions between the ground-state S and D atoms at energies from 1.0×10-11 to 1.0×10-4 a.u. when the two atoms approach each other along the SDX2Π interaction potential. No shape resonances can be found in the total elastic cross sections. The results show that the shape of the total elastic cross sections is mainly dominated by the s-partial wave at very low temperatures. Because of the weakness of the shape resonances coming from various partial waves, they are all covered up by the strong total elastic cross sections.