SPECTROSCOPIC CONSTANTS OF THE X (2)SIGMA(- COMPARISON WITH EXPERIMENT() AND A (2)PI STATES OF SR+AR FROM FIRST PRINCIPLES )

We present the first nonempirically calculated spectroscopic constants for the recently observed [J. Chem. Phys. 105, 2167 (1996)] ground (X (2) Sigma(+)) and excited (A (2) Pi) states of Sr+Ar. Our best result s yield D-e = 694 cm(-1), R-e = 3.662 Angstrom, and omega(e) = 38.7 cm (-1) for the ground and D-e = 1967 cm(-1), R-e = 3.169 Angstrom, and o mega(e) = 99.1 cm(-1) for the excited state. The calculated D-e's are within the error bars of the experimentally determined one for the gro und state favoring the low end and underestimate the corresponding one for the excited state by about 7% The equilibrium separations (R-e's) for the two states have not been experimentally determined, however o ur results accurately reproduce the estimated shift, Delta R-e, betwee n the two states. The interaction is mainly electrostatic for the grou nd state for which the contribution of dynamic electron correlation wa s found to be more important than for the excited state. (C) 1997 Amer ican Institute of Physics.