白钨矿结构的钨、钼酸盐晶体的光吸收边及其起因

Optical Absorption Edges and their Origin of Scheelite Structured Tungstate and Molybdate Crystals

比较了一些白钨矿结构的钨、钼酸盐晶体（如未掺杂的ＣａＷＯ４、ＰｂＷＯ４、ＣａＭｏＯ４、Ｐｂ－ＭｏＯ４晶体）的透射光谱，发现这些晶体的光吸收边的相对位置用普遍认同的观点，即白钨矿结构的钨、钼酸盐晶体的光吸收边起源于具有Ｔｄ对称性的Ｗ（Ｍｏ）Ｏ２－４基团内的电子从ｔ１轨道向２ｅ轨道的转移激发，不能给出圆满阐释，而应代之以新的观点。作者认为这类晶体的光吸收边可能起因于Ｄ２ｄ对称的Ｗ（Ｍｏ）Ｏ２－４基团内的电子从１ａ２轨道向２ｂ１轨道的转移激发，并借助于离子极化的模型对这些未掺杂晶体以及分别掺Ｌａ、Ｍｏ和Ｎｂ的ＰｂＷＯ４晶体的光吸收边的相对位置进行了定性解释。

The transmission spectra and optical absorption edges (OAEs) of some scheelite structured crystals, such as undoped CaWO 4, PbWO 4, CaMoO 4 and PbMoO 4 crystals, were comparatively studied. It was found that the relative location of their OAEs can not be explained from a widely adopted viewpoint that the OAEs originate from electron transfer from t 1 orbital to 2e orbital of W(Mo)O 2- 4 group with T d symmetry. But it can be explained with the electron transfer from 1a 2 orbital to 2b 1 orbital within the W(Mo)O 2- 4 group with D 2d  symmetry. The OAEs of the above mentioned crystals and the PbWO 4 crystals doped with lanthanum, niobium and molybdenum respectively were interpreted briefly from the present viewpoint and the ion polarization model.