EPR OF [TIO4/LI]B0 AND RELATED CENTERS IN X-IRRADIATED ALPHA-QUARTZ

The centre [TiO4/Li]B0 in crystalline quartz has been studied in detail by single-crystal electron paramagnetic resonance (EPR) spectroscopy. Between 35 and 120 K, [TiO4/Li]B0 exhibits C2 symmetry. The hyperfine matrix of Li-7 and the hyperfine and nuclear quadrupole matrices of the low-abundance isotope Ti-49 have been measured at both temperatures. A comparison with [TiO4/Li]A0 is made and a model is proposed for the spin population distribution in [TiO4/Li]B0 as well as for the location for the lithium ion within the centre. A third lithium centre, [TiO4/Li]gamma-0, was also discovered, but has not yet been fully characterized. Another newly discovered species, called [TiO4/Na]beta-0, has also been studied. Between 35 and 100 K. [TiO4/Na]B0 exhibits C1 symmetry. The line widths of the signals from [TiO4/Li]B0, [TiO4/Li]gamma-0 and [TiO4/Na]beta-0 were studied as a function of temperature in the range ca 35-120 K, above which the signals broadened beyond observability. All three centres were found to decay slowly at room temperature over several days.