Theoretical Study on the Potential Energy Curve and Vibration-rotation Spectra of BeF Radical

T The potential energy curve(PEC)of BeF(X<'2>Σ<'+>)radical is investigated by using the complete active space self-consistent field(CASSCF)method followed by the highly accurate valence internally contracted multireference configuration interaction(MRCI)approach over the internuclear separation range from 0.0522 to 2.0472 nm. The PEC is fitted to the analytic Murrell-Sorbie function, which is employed to accurately determine the spectroscopic parameters.The present D<,0>, D<,e>, R<,e>, ω<,e>, ω<,e>χ<,e>, α<,e> and B<,e> are 6.14 eV, 6.22 eV, 0.1372 nm, 1236.12 cm<'-1>, 9.11 cm<'-1>,0.0175 cm<'-1> and 1.4651 cm<'-1>, respectively. These parameters hav0e been compared with those of previous investigations reported in the literature. With PEC determined at the present level of theory,a total of 75 vibrational states have been predicted for the first time by numerically solving the radial Schrfidinger equation of nuclear motion using the Numerov method. For each vibrational state,the complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined for the first time. Comparing with the available experiments and other theories, we find that the present spectroscopic parameter and molecular constant results are more accurate and complete than the previous theoretical investigations.