Accurate potential energy function and spectroscopic study of the X2Σ+, A2Π and B2Σ+ states of the CP radical

This paper calculates the equilibrium internuclear separations, the harmonic frequencies and the potential energy curves of the X-2 Sigma(+), A(2)Pi and B-2 Sigma(+) states of the CP radical by the highly accurate valence internally contracted multireference configuration interaction method with correlation-consistent basis sets (aug-cc-pV6Z for C atom and aug-cc-pVQZ for P atom). The potential energy curves are all fitted with the analytic potential energy function by the least-square fitting. Employing the analytic potential energy function, we determine the spectroscopic constants (B-e, alpha(e), and omega(e)x(e)) of these states. For the X-2 Sigma(+) state, the obtained values of D-e, B-e, alpha(e), omega(e)x(e), R-e and omega(e) are 5.4831 eV, 0.792119 cm(-1), 0.005521 cm(-1), 6.89653 cm(-1), 0.15683 nm, 12535.11 cm(-1), respectively. For the A(2)Pi state, the present values of D-e, B-e, alpha(e), omega(e)x(e), R-e and omega(e) are 4.586 eV, 0.703333 cm(-1), 0.005458 cm(-1), 6.03398 cm(-1), 0.16613 nm, 1057.89 cm(-1), respectively. For the B-2 Sigma(+) state, the present values of D-e, B-e, alpha(e), omega(e)x(e), R-e and omega(e) are 3.506 eV, 0.677561 cm(-1), 0.00603298 cm(-1), 5.68809 cm(-1), 0.1696 nm, 822.554 cm(-1), respectively. For these states, the vibrational states with the rotational quantum number J equals zero (J = 0) are studied by solving the radial nuclear Schrodinger equation using the Numerov method. For each vibrational state, the vibrational level, the classical turning points, the rotational inertial and the centrifugal distortion constants are calculated. Comparison is made with recent theoretical and experimental results.