NMR-STUDY OF LI-7 AND B-11 NUCLEI IN NONLINEAR-OPTICAL LIB3O5 SINGLE-CRYSTAL

The nuclear magnetic resonances of the Li-7 and B-11 nuclei in a singl e crystal of LiB3O5 (LBO), grown by the top seeded slow cooling method , have been investigated by empolying Bruker MSL 200S pulsed NMR spect rometer at room temperature. There have been some NMR studies on this crystal but no experimental determination of the quadrupole interactio n parameter. We observed the NMR signals consistent with crystallograp hic data around the Larmor frequency of 77.77 MHz for Li-7 nucleus and 64.20 MHz for B-11 nucleus. Through angular dependence measurements o f the spectra on the ab-, bc-, and ca-plane, the electric field gradie nt (EFG) tensors of the nuclei are determined. The quadrupole coupling constant (e(2)qQ/h) and asymmetry parameter (eta) are as follows; Li- 7 : e(2)qQ/h\ = 144 +/- 4 kHz, eta = 0.62 +/- 0.05, B-11(1) : \e(2)qQ/ h\ = 2.60 +/- 0.10 MHz, eta = 0.47 +/- 0.25, B-11(2) : \e(2)qQ/h\ = 17 4 +/- 4 kHz, eta = 0.56 +/- 0.01, B-11(3) : \e(2)qQ/h\ = 2.52 +/- 0.10 MHz, eta = 0.51 +/- 0.22.