The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA.
J Chem Phys. 2011 Jan 21;134(3):034703. doi: 10.1063/1.3528116.
The sticking coefficient for D(2)O impinging on crystalline D(2)O ice was determined for incident translational energies between 0.3 and 0.7 eV and for H(2)O on crystalline H(2)O ice at 0.3 eV. These experiments were done using directed molecular beams, allowing for precise control of the incident angle and energy. Experiments were also performed to measure the intensity and energy of the scattered molecules as a function of scattering angle. These results show that the sticking coefficient was near unity, slightly increasing with decreasing incident energy. However, even at the lowest incident energy, some D(2)O did not stick and was scattered from the ice surface. We observe under these conditions that the sticking probability asymptotically approaches but does not reach unity for water sticking on water ice. We also present evidence that the scattered fraction is consistent with a binary collision; the molecules are scattered promptly. These results are especially relevant for condensation processes occurring under nonequilibrium conditions, such as those found in astrophysical systems.
D(2)O 撞击晶态 D(2)O 冰的附着系数，对于 0.3 到 0.7 eV 的入射平移能，以及对于 0.3 eV 的 H(2)O 在晶态 H(2)O 冰上的附着系数，已被确定。这些实验是使用定向分子束进行的，允许精确控制入射角和能量。实验还进行了测量散射分子的强度和能量作为散射角的函数。这些结果表明，附着系数接近 1，随着入射能量的降低略有增加。然而，即使在最低的入射能量下，也有一些 D(2)O 没有附着并从冰表面散射。在这些条件下，我们观察到，对于水在水冰上的附着，附着概率渐近地接近但不达到 1。我们还提供了证据表明，散射部分与二进制碰撞一致;分子被迅速散射。这些结果对于在非平衡条件下发生的冷凝过程特别相关，例如在天体物理系统中发现的那些。
