Spectroscopic investigations on NO^ + (X^1\varSigma ^ + , a^3\varSigma ^ + , A^1\varPi) ion using multi-reference configuration interaction method and correlation-consistent sextuple basis set augmented with diffuse functions #br#

Three low-lying electronic states (X^1\varSigma ^ + , a^3\varSigma ^ + , and A^1\varPi) of NO^ + ion are studied using the complete active space self-consistent-field (CASSCF) method followed by highly accurate valence internally contracted multi-reference configuration interaction (MRCI) approach in combination of the correlation-consistent sextuple basis set augmented with diffuse functions, aug-cc-pV6Z. The potential energy curves (PECs) of the NO^ + (X^1\varSigma ^ + , a^3\varSigma ^ + , A^1\varPi) are calculated. Based on the PECs, the spectroscopic parameters R_\rm e, D_\rm e, \omega _\rm e, \omega _\rm e\chi _\rm e, \alpha _\rm e, B_\rm e, and D_0 are reproduced, which are in excellent agreement with the available measurements. By numerically solving the radial Schr\"odinger equation of nuclear motion using the Numerov method, the first 20 vibrational levels, inertial rotation and centrifugal distortion constants of NO^ + (X^1\varSigma ^ + , a^3\varSigma ^ + , A^1\varPi) ion are derived when the rotational quantum number J is equal to zero (J = 0) for the first time, which accord well with the available measurements. Finally, the analytical potential energy functions of these states are fitted, which are used to accurately derive the first 20 classical turning points when J = 0. These results are compared in detail with those of previous investigations reported in the literature.