Effect of air annealing on the spectral properties of Ce : Y3Al5O12 single crystals grown by the temperature gradient technique

Five absorption hands, at 227, 300 340, 370 and 457nm, were observed in the optical absorption spectrum of Ce:Y3Al5O12 (Ce:YAG) crystals grown by the temperature gradient technique (TGT). The absorption bands at 227, 340, and 457 nm were identified Lis belonging to the Ce3+ -ion in the YAG crystal. A near UV optical emission band at 398nm was observed. with an excitation spectrum containing two bands, at 235 and 370nm. No fluorescence was detected under 300 nm excitation. The pair of absorption bands at 235 and 370 nm and the absorption band at 300 nm were attributed to the F- and F+-type color centers, respectively. The color centers model was also applied to explain the spectral changes in the Ce:YAG (TGT) crystal, including the reduction in the Ce 31 -ion absorption intensity, after annealing in an oxidizing atmosphere (air). (C) 2004 Elsevier B.V. All rights reserved.

Color centers and charge state change in Ce : YAG crystals grown by temperature gradient techniques

Color centers and impurity defects of Ce:YAG crystals grown in reduction atmosphere by temperature gradient techniques have been investigated by means of gamma irradiation and thermal treatments. Four absorption bands associated with color centers or impurity defects at 235, 255, 294 and 370 nm were observed in as-grown crystals. Changes in optical intensity of the 235 and 370 nm bands after gamma irradiation indicate that they are associated with F+-type color center. Charge state change processes of Fe3+ impurity and Ce3+ ions take place in the irradiation process. The variations of Ce3+ ions concentration clearly indicate that Ce4+ ions exist in Ce:YAG crystals and gamma irradiations could increase the concentration of Ce3+ ions. Annealing treatments and the changes in optical density suggest that a heterovalent impurity ion associated with the 294 nm band seems to be present in the crystals. (c) 2005 Elsevier B.V. All rights reserved.

豌豆β-微管蛋白基因的分离

微管蛋白是在进化过程中最为保守的蛋白质中的一组。高等植物的微管蛋白基因与酵母的微管蛋白基因具有同源性。据此进行了如下实验：从豌豆（A561），大豆（黑农26）苗中提出的核DNA用EcoRI、BamHI和SalI限制性内切酶酶切，经Southern转移与32P标记的酵母β-微管蛋白cDNA进行杂交。从杂交图谱上可以看出豌豆、大豆均有两个拷贝的β-微管蛋白基因。豌豆核DNA经BamHI酶切后的5kb和10kb两个片段从电泳凝胶中回收，插入到puc9质粒中，宿主菌为JM83。然后以酵母β-微管蛋白基因为探针，用菌落原位杂交和Southern斑点杂交的方法筛选出含有豌豆β-微管蛋白基因编码序列的克隆。所克隆到的DNA序列的限制性酶切图谱及序列分析尚有待进一步研究。