2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/23647The role of $S$-mixing in the quantum tunneling of the magnetization in nanomagnets has been investigated. We show that the effect on the tunneling frequency is huge and that the discrepancy (more than 3 orders of magnitude in the tunneling frequency) between spectroscopic and relaxation measurements in Fe$_8$ can be resolved if $S$-mixing is taken into account.REVTEX, 10 pages, 3 jpg figures, to appear in PRLOther Condensed Mattertext