We report a \^{23}Na and \^{27}Al nuclear magnetic resonance (NMR)investigation of low-silica X (LSX) zeolite with chemical formulaNa_{12}Al_{12}Si_{12}O_{48} (Na_{12}-LSX) loaded with n additional guest sodiumatoms. Na_{n}/Na_{12}-LSX exhibits an insulator-to-metal transition aroundn=11.6, which is accompanied by a significant enhancement of bulk magneticsusceptibility. Paramagnetic moments are thermally activated in the metallicNa_{12}/Na_{12}-LSX with an activation energy of around 0.1 eV. At the sametime, a new shifted component (SC) appears in the \^{23}Na NMR, whose large andpositive NMR shift scales with bulk magnetic susceptibility. Its spin-latticerelaxation rate 1/T_{1} is governed by the fluctuations determined by the sameactivation energy as obtained from the bulk magnetic susceptibility data. Thetimescale of these fluctuations is typical for atomic motions, which suggeststrong electron-phonon coupling, a hallmark of polaron states. Theinsulator-to-metal transition in Na_{n}/Na_{12}-LSX is thus discussed within apolaron model.
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