辐照绿柱石的色心与赋色机制

COLOR CENTER AND COLORING MECHANISM OF IRRADIATED BERYL

在不同辐照剂量的带电粒子作用下 ,四川无色绿柱石因赋色而呈现浅蓝色、蓝绿色、黄绿色、浅黄色及橙黄色。紫外可见吸收光谱 ( UV-VIS)和阴极发光光谱 ( CLS)研究表明 ,辐照绿柱石中存在两组与赋色密切相关的色心组合 ,其一为相对稳定的[Fe3 + ] OH和 [Fe3 + 4] S心 ;其二则为不稳定的 [H0 ] i心和 F+ 心。二者对可见光的能量分别具有不同程度的选择性吸收和发射 ,由此产生特征的吸收与发射光谱。低温退火处理 ( 2 10°C) ,有助于消除辐照绿柱石中不稳定的色心 ,使相对稳定的 [Fe3 + ] OH心浓度再度聚集 ,并形成新的缺陷 (二次缺陷 ) ,进而提高稳定色心的主波长和饱和度。研究证实 ,二次缺陷形成的初始温度 ,可近似代表辐照绿柱石的最佳热固色温度点。经辐照与热固色作用而形成的黄色、橙黄色绿柱石的颜色相对稳定 ,并不因长期日照或低温受热( <2 80°C)而褪色。

Affected by the charged particles with different amounts of irradiation, the colorless beryl in Sichuan and Xinjiang Provinces are colored into light blue, blue green, yellow green, light yellow and orange yellow. The research on the UV VIS spectrum and CLS spectrum shows that two groups of color center assemblages associated with the coloring mechanism are present in the irradiated beryl crystal. The first group is defined as the centers of [Fe 3+ ] OH and [Fe 3+ 4] S, relatively stable, and the second is defined as the centers of i and F +, unstable. The two groups may selectively absorb and emit in different degrees the energy of the visible light, resulting in their corresponding characteristic absorptions and luminescence spectra. The low temperature annealing treatment (210 °C )may help to eliminate the unstable color center in the irradiated beryl, re concentrating the center of relatively stable [Fe 3+ ] OH resulting in new defects (secondary defects), and increasing the main wavelength and color saturation of the stable color. The research also indicates that the temperature resulting from the secondary defects may represent approximately the optimum temperature for the thermal color concentration. The colors of the irradiated yellow, orange yellow beryl are relatively stable and free of color deterioration resulting from long time sunshine or low temperature heat (<280 °C ).