S. Magnier et P. Millie, POTENTIAL CURVES FOR THE GROUND AND NUMEROUS HIGHLY EXCITED ELECTRONIC STATES OF K-2 AND NAK, Physical review. A, 54(1), 1996, pp. 204-218
Potential curves of the K-2 and NaK molecules have been computed in th
e framework of pseudopotential methods, over a wide range of interatom
ic distances. At short internuclear distances, the agreement with expe
rimental data is excellent, the mean deviation between theoretical and
experimental spectroscopic constants being 1% for the two alkali dime
rs. At large interatomic separation, wells and avoided crossings are o
bserved in adiabatic potential curves of highly excited states correla
ted to the asymptotes close to K[4p]+K[4p] and Na[3p]+K[4p]. For examp
le, the well depths of the (1) Sigma(+) states reach 2650 cm(-1) for K
-2 and 4330 cm(-1) in the case of NaK. We demonstrate that they corres
pond to pseudocrossings between covalent states (dissociating into K[n
l]+K[n'1'] or Na[nl]+K[n'l']) and ionic states (correlated to K++K- fo
r K-2, Na++K-, or Na-+K+ for NaK, the negative ion being in the ground
state or an autoionizing state). As for Na-2, these structures may pl
ay a crucial role in the interpretation of low-energy collisions.