Singlet and triplet Σ+ excited states of NaH and KH: undulating potential energy curves

The 1Σ+ and 3Σ+ states of NaH dissociating into the 3s–5s states of Na and the 1Σ+ and 3Σ+ states of KH dissociating into the 4s–6p states of K are calculated using the effective core potential with the core polarization potential and the configuration interactions. Apart from ionic-neutral avoided crossings in cascade for the singlet states and neutral-neutral avoided crossings in both singlet and triplet states, all these states also show the undulating potential curves discovered recently: Phys. Rev. A 59 (1999) 1178–1186. The apparently complex potential curves are analyzed in this work.