海南蓬莱蓝宝石的光致发光谱学特征及意义

从光致发光光谱角度探讨了海南蓬莱蓝宝石的呈色机理.结果发现:与蓝宝石吸收光谱的500～700 nm吸收宽带相比,在500～720 nm发光波段内存在566.8 nm锐峰、600 nm左右肩峰和Cr~(3+)的694.2 nm特征峰.600 nm肩峰与其吸收峰镜像对称,566.8 nm处锐峰的产生原因复杂.600 nm肩峰可能与Fe~(2+)-Fe~(2+)离子对的电子跃迁有关;566.8 nm锐峰因532 nm激光激发Fe~(2+)-Ti~(4+)或Fe~(2+)-Fe~(3+)间的电荷迁移带,通过晶格造成Si~(4+)、Mg~(2+)等微量杂质离子敏化而产生.光致发光谱中呈现更多谱峰,能呈现离子跃迁时不同离子间发生的相互作用,为500～700 nm吸收宽带由不同致色机制的叠加给出了直接证明,是一种能全面地研究宝石矿物中致色元素能级结构的有效方法.

A Study on Photoluminescence Spectroscopy of Sapphire from Penglai, Hainan

Coloration mechanism of sapphire from Penglai Town, Hainan Province, was discussed with the method of photoluminescence (PL) spectra. Compared with 500 ～700 nm absorption wide spectral band, there are two peaks at 566. 8 and 600 nm, and a characteristic peak of Cr~(3+) at 694. 2 nm in the 500 ～ 720 nm luminescence spectra of sapphire. The 600 nm shoulder peak is mirror symmetrical to its corresponding absorption peak, and the causes of 566. 8 nm narrow peak are complex. The 600 nm shoulder peak could be due to the electron transition of the ex-change-coupled Fe~(2+) - Fe~(2+) pair, and the 566. 8 nm narrow peak could be due to the sensitization of Si~(4+) and Mg~(2+) i-ons through crystal lattice when Fe~(2+)- Ti~(4+) or Fe~(2+)- Fe~(3+) charge transfer bands is activated by 532 nm laser. More peaks are presented in PL spectra, providing a direct proof that PL spectra is the presentation of interactions among different coloration mechanisms. With further development, the technology of PL spectra might become an effective method for analyzing the energy level structures of colorgenous elements in gems.