Double minimum potential well, enhancement

Historically, the first method for enhancing one-photon PA so that lower-u, more deeply bound vibrational levels could be directly produced was the use of upper-state potential energy curves having two minima with an intervening barrier [107, 122]. Such double-minimum potentials are well known in the alkali metal dimers (e.g., [123-125]). The 0 state of Cs2 has been studied in some detail because the production of molecules in more deeply bound levels is favored [126,127]. Other promising double-minimum states have been proposed for study [40,128]. Of particular significance in each case is the energy and intemuclear distance at which... 

The characterization of the X and a state levels of homonuelear and heteronuclear alkali dimer molecules formed by decay of the upper levels formed by photoassociation is discussed next. Resonance-enhanced multiphoton ionization is shown to be a powerful technique for establishing the population of vibrational levels formed in the X and a states near the dissociation limit. A new ion depletion technique for observing rotational and hyperfine structure as well for these levels near dissoeiation is also discussed. To reach lower levels, especially in the ground X state, it is useful to select specific photoassociation approaches such as double minimum excited-state potentials, resonant coupling of two (or more) excited state potentials, and stimulated Raman transfer from levels near dissociation to low levels (e.g., the collisionally stable V = 0,J = 0 level). 

---