Investigations on molecular constants of the CD（X^2∏） radical and elastic collisions between ground-state C and D atoms at low temperatures

The potential energy curve of the CD(X~2Π) radical is obtained using the coupled-cluster singles-doublesapproximate-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,ωeχe,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¨odinger 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(X~2Π) 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 4 a.u.when the two atoms approach each other along the CD(X~2Π) 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.