Tunneling isomerization of molecules with symmetric double well potentials are associated with periodic nuclear fluxes, from the reactant R to the product P and back to R. Halfway between R and P the fluxes achieve their maximum values at the potential barrier. For molecules in the lowest tunneling doublet (v = 0) the rises and falls to and from the maximum values are approximately bell-shaped. Upon excitation to higher tunneling doublets v = 1, 2, etc., however, this shape is replaced by symmetric “staircase patterns” of the fluxes, with v + 1 stepping up and down in the domains of R and P, respectively. The quantum derivation of the phenomenon is universal. It is demonstrated here for a simple model of nuclear fluxes during tunneling isomerization of ammonia along the umbrella inversion mode, with application to separation of isotopomers.