Raut U, Teolis B D, Loeffler M J, Vidal R A, Famá M, Baragiola R A
Laboratory of Atomic and Surface Physics (LASP), University of Virginia, Charlottesville, Virginia 22904, USA.
J Chem Phys. 2007 Jun 28;126(24):244511. doi: 10.1063/1.2746858.
We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface area of the pores, signaled by infrared absorption by dangling bonds, precedes the decrease in the pore volume during irradiation. Our results imply that impacts from cosmic rays can cause compaction in the icy mantles of the interstellar grains, which can explain the absence of dangling bond features in the infrared spectrum of molecular clouds.
我们研究了在40K下高能离子对气相沉积非晶态固体水的压实作用。通过紫外-可见光谱、红外光谱和甲烷吸附/脱附对孔隙率进行了表征。这三种技术提供了关于辐照导致冰结构变化的不同且互补的观点。我们发现，在辐照过程中，由悬键的红外吸收所表明的孔隙内表面积的减小先于孔隙体积的减小。我们的结果表明，宇宙射线的撞击会导致星际尘埃冰质幔层的压实，这可以解释分子云红外光谱中悬键特征的缺失。
