We analyze three-body nonadditive interactions and characterize critical points on potential energy surfaces of the lowest A2B (A,B = Li, Na, K, Rb, Cs) quartet states using high-level ab initio calculations. Our calculations indicate that near equilibrium geometries, large nonadditive effects are stabilizing the systems.
We also show that trimer formation reactions are always energetically allowed even for low-lying rovibrational states of heteronuclear triplet-Sigma dimers.