Investigations on molecular constants of the CD(X2П) radical and elastic collisions between ground-state C and D atoms at low temperatures
Chin. Phys. B, 2009, 18 (9):
The potential energy curve of the CD(X2П ) radical is obtained using the coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions, aug-cc-pV5Z. The potential energy curve is fitted to the Murrell--Sorbie function, which is used to determine the spectroscopic parameters. The obtained D0, De, Re, ωe, ωeχ e, αe and Be values are 3.4971~eV, 3.6261~eV, 0.11197~nm,
2097.661~cm-1, 34.6963~cm-1, 0.2083~cm-1 and 7.7962~cm-1, respectively, which conform almost perfectly to the available measurements. With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory, a total of 24 vibrational states have been predicted for the first time when J = 0 by solving the radial Schr?dinger equation of nuclear motion. The complete vibrational levels, the classical turning points, the inertial rotation constants and centrifugal distortion constants are reproduced from the CD(X2П) potential when J = 0, and are in excellent agreement with the available measurements. The total and the various partial-wave cross sections are calculated for the elastic collisions between the ground-state C and D atoms at energies from 1.0× 10-11 to 1.0× 10-4a.u. when the two atoms approach each other along the CD(X2П) potential energy curve. Only one shape resonance is found in the total elastic cross sections, and the resonant energy is 8.36× 10-6~a.u. The results show that the shape of the total elastic cross section is mainly dominated by the s partial wave at very low temperatures. Because of the weak shape resonances coming from higher partial waves, most of them are passed into oblivion by the strong total elastic cross sections.