Design and Construction of a Grazing Incidence X-Ray Reflection System for Liquid-Vapor Interfaces

我们利用传统的x射线管（Cu K_< α >,2.2kW）研制了一种掠入射的液-气界面x射线反射装置。由于液体表面是水平的限制，需要一种特殊的几何形状。我们设备的主要特点如下。使用不对称切割的Ge（111）晶体单色材料产生高度准直和单色的x射线光束。利用探测量子效率高、量化噪声低、动态范围宽的成像板作为二维区域探测器。样品位置缓慢升高，以补偿测量期间的蒸发。用环形法测量表面张力的装置与反射装置相结合，使原位测量成为可能。该系统通过测量自由水面的x射线反射率剖面进行了测试。我们得到的结果与使用同步辐射的Braslau et al.（1985）报道的结果一致。对几种液态烷烃和醇进行了研究，并根据分子大小和形状的表面粗糙度特征解释了反射率分布。尽管使用传统的x射线管，但我们的反射系统的动量传递分辨率高于Braslau等人的同步辐射系统。

We have developed a grazing incidence x-ray reflection apparatus for liquid-vapor interfaces using a conventional x-ray tube (Cu K_<alpha>,2.2kW). A special geometry has been necessitated by the restriction that the liquid surface is horizontal. The main features of our apparatus are as follows. Highly collimated and monochromated x-ray beams are generated using an asymmetrically cut Ge (111) crystal monochromater. An imaging plate, which has a high detective quantum efficiency, a low quantization noise and a wide dynamic range is used as a 2-dimensional area detector. The sample position is slowly elevated to compensate for evaporation during measurements. A device for surface tension measurement by the ring method has been combined with the reflection apparatus so that in situ measurements may be possible.This system was tested by measuring X-ray reflectivity profiles from the free surface of water. We obtained a good agreement with the result reported by Braslau et al. (1985) who used synchrotron radiation. Several liquid alkanes and alcohols have been investigated and the reflectivity profiles have been interpreted in terms of a surface roughness characteristic of the size and shape of the molecules.In spite of using a conventional x-ray tube, the resolution in the momentum transfer of our reflection system is higher than that of synchrotron radiation system by Braslau et al..