[en] Metastable ion Coulomb crystal (ICC) in the polychromatic optical superlattice (OSL) created by so-called rectified gradient forces is studied. Our analysis is based on the numerical solution of the nonlinear stochastic differential equations taking into account the trapping and dissipative forces, their quantum fluctuations, and Coulomb repulsion of ions. The key question is how long will this metastable highly ordered crystalline structure persist. The critical parameter determining the ICC destruction times t_d is the OSL period L (at fixed intensity values of the optical fields). Our simulations demonstrate that t_d of the ICC, consisting of several tens of mercury ions, experiences giant changes (by four orders of magnitude) at relatively slight variations of the optical superlattice period L in the range from 0.35 to 0.70 mm. We have shown that the dependence t_d (L) can be approximated by the Arrhenius-like equation with an effective activation energy which is nonlinearly dependent on the OSL period L. These results explain the ultrahigh sensitivity t_d (L) to the OSL period L and show how to adjust L to ensure all-optical confinement of ICC in the OSL from a fraction of a second to one and half minutes. Graphical abstract:

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