Structure of interstellar carbonaceous dusts and their surface.

淬火碳质复合材料(QCC)是由碳氢等离子体喷射物凝聚而成的碳质材料。Sakata和他的同事们已经证明了QCC具有220 nm的吸收特征，这是一组与反射星云、撞击区域和行星星云中的红外发射特征相对应的红外吸收带，并显示出与反射星云中看到的扩展的红色发射相匹配的可见荧光。这些性质使QCC成为实验室中类似于星际介质中碳质物质的有力候选材料。高分辨率透射电子显微镜(HRTEM)显示，暗QCC是碳质洋葱状粒子的凝聚。每个粒子由多个壳组成，许多粒子的中心有一个空洞。HRTEM图像表明，颗粒结构中有许多缺陷位，通过氢气暴露QCC，暗QCC颗粒中的缺陷位很容易与氢分子反应。结果表明，暗-QCC的3.42、3.51、6.9、7.3、12.5微米红外吸收峰强度增大，而220 nm吸收峰稳定。另一方面，薄膜QCC在紫外光(222 Nm)照射和黑暗条件下都不与氢发生反应。为了阐明分子云化学，我们需要对候选材料的表面进行更多的研究。

Quenched Carbonaceous Composite (QCC) is a carbonaceous material condensed from an ejecta of hydrocarbon plasma. A.Sakata and his colleagues have shown that QCC has a 220 nm absorption feature, a set of infrared absorption bands that correspond to the infrared emission features in reflection nebulae, HIT regions, and planetary nebulae, and exhibits visible fluorescence matching the extended red emission seen in reflection nebulae. These properties make Q CC a strong candidate material as a laboratory analog to the carbonaceous material in the interstellar medium.High-resolution transmission electron micrographs (HRTEM) revealed that the dark-QCC is a coagulation of carbonaceous onion-like particles. Each particle consists of multiple shells, and many of the particles have a void at the center. The HRTEM images implied that the particles have many defected sites in their structure.By exposuring of the QCC with hydrogen gas, the defected sites in the dark-QCC particles were reacted with hydrogen molecules easily. As a result, peak intensities of infrared absorption bands at 3.42, 3.51, 6.9, 7.3, 12.5mum were increased, However, the 220 nm absorbance peak of the dark-QCC was stable. On the other hands, the filmy-QCC did not react with hydrogen both under irradiation of uv (222nm) and under dark condition.In order to clarify molecular cloud chemistry, we need more studies about the surface of the candidate materials.