用D／max－rBX光机实现EXAFS测量

EXAFS Measurement in D/max-rB X-ray Dmractometer

分析了同步辐射和普通Ｘ射线源的巨大差别，计算了在Ｄ／ｍａｘ－ｒＢＸ光机上进行ＥＸＡＦＳ（ＥｘｔｎｄｅｄＸ－ｒａｙＡｂｓｏｒｐｔｉｏｎＦｉｎｅＳｔｒｕｃｔｕｒｅ）测量光强计数、能量分辨率、高次谐波等主要参数的限度。为了获得能够用于结构研究的ＥＸＡＦＳ谱线，采取了一系列措施，如选用合适的靶材、工作电压电流、单色器晶体、狭缝、单道分析器等。作者强调探测器的有限线性范围是产生系统误差的主要原因之一，在实验室ＥＳＡＦＳ测量中，总存在ｘ射线光强与分辨能力的矛盾与协调问题，为此，计数率必须控制在２×１０４ＣＰＳ以下。最后，报道了在ＲｉｇａｋｕＤ／ｍａｘ－ｒＢＸ射线衍射仪上的一个实例结果。并分析了实验室测量的局限性。

he great difference between synchrotron radiation sources andconventiOnalX-ray sources in EXAFS measurements is analyed. The limits of X-ray intensltycounts, energy resolu-tion and higher harmonics in the use of D/ max- rB X-ray diffractometer are calclllated.Proper precautions (target material, oporating voltage and current, monochromator cryStal,slit width,single channel analyzer)are taken to provide EXAFS spectra of acceptable qua- luty for structural study.It is emphasised that a major source of the systematic errors arises from the finite dynamic range of detectors,so the count rate must be under 2 × 104cps。There is always a trade-off between intensity and resolution in EXAFS measurements at lab-oratories. Finally,a real EXAFS measurement result by the use of Rigaku D/max-rB X-ray diffractometer at the lab of Hohai Univ. is reported. The limitation of laboratory EX-AFS is analysed.