6533b7d3fe1ef96bd125fe28

RESEARCH PRODUCT

Optical Properties of Natural and Synthetic Beryl Crystals

subject

description

The results of investigation of photoluminescence and UV-Visible absorption spectra of natural beryl crystals from Ural Mountains before and after fast neutron irradiation and synthetic crystal grown in Belarus and Russia are presented. Photoluminescence (PL) spectra of synthetic beryl crystals contain a broad band with maxima 740 nm excited both by UV light (λex = 260 nm, 271 nm) and laser excitation (λex =263 nm). This band is connected with Fe 2+ ions. The temperature lowering down to 8 K leads to appearance of narrow lines in the 680 - 720 nm regions. Emission lines observed in the luminescence spectra are connected with electron transition 2 Eg→ 4 A2g of the Cr 3+ ions: R-lines (682.5 nm) arise from isolated Cr 3+ ions occupying AI 3+ sites; N-lines (691, 698, 703, 706 and 711 nm) arise from several types of exchange-coupled pairs of Cr 3+ ions occupying first, second and third nearest and related neighbour AI 3 + sites. It is shown that the absorption bands in the 690-580 nm region of natural pale blue beryl crystals caused by neutron irradiation belong to a complex center, which consists of Cr 3+ ions and radiation defect - F or F + - center. Presence of Fe 2+ ions contributes to the persistence of the complex defect.