MAGNETIC AND OPTICAL-PROPERTIES OF SODIUM CLUSTERS IN ZEOLITE LTA

Cationic Na clusters are formed in the alpha and beta cages of Na-form LTA by incorporating Na atoms from vapor. The maximum number of Na at oms incorporated is 4.9 per unit cell. Ac magnetic susceptibilities an d optical reflection spectra are measured as a function of Na loading density. Na clusters show diamagnetism independent of Na loading densi ty while K clusters in K-LTA and Rb clusters in Rb-LTA show ferromagne tism at certain loading densities. All Na clusters contain therefore a n even number of the electrons, which are supplied from 3s-electrons o f the guest Na atoms, irrespective of the cages they are formed. The e lectron-phonon interaction plays an important role in stabilizing the singlet state. In the reflection spectra of highly loaded sample, a st rong band is observed at 1.95 eV. An oscillator strength of this band exceeds unity per cluster by a great deal. This band is assigned to su rface-plasmon-like excitation of Na cluster formed in alpha cage.