Mozejko Paweł, Bass Andrew D, Parenteau Luc, Sanche Léon
Groupe en Sciences des Radiations, Faculté de Medecine, Université de Sherbrooke, Sherbrooke, Québec J1H5N4 Canada.
J Chem Phys. 2004 Nov 22;121(20):10181-9. doi: 10.1063/1.1807813.
The results of D(-) ion desorption induced by 3-20 eV electrons incident on condensed CD(4), C(2)D(6), C(3)D(8), C(2)D(4), and C(2)D(2) are presented. These compounds were deposited in submonolayer amounts on the surfaces of multilayer solid films of Kr and nonporous and porous amorphous ice. While desorption of the D(-) anions proceeds via well-known processes, i.e., dissociative electron attachment (DEA) and dipolar dissociation, significant perturbations of these processes due to presence of the different film substrates are observed. We have shown that it is possible to distinguish between the character and nature of these perturbations. The presence of the nonporous ice perturbs the D(-) desorption intensity by affecting the intrinsic properties of the intermediate anion states through which dissociation proceeds. On the other hand, the presence of the porous ice introduces extrinsic effects, which can affect electron energy losses prior to their interaction with the hydrocarbon molecule and/or the energies and intensities of the fragment species after dissociation. Simple mechanisms responsible for the observed variations in the intensities of desorbed anionic signals are proposed and discussed. Electron transfer from transient anion states to electron states of the substrate film or nearby hydrocarbon molecules appear as the most efficient mechanism to reduce the magnitude of the DEA process.
本文展示了3 - 20电子伏特的电子入射到凝聚态的CD₄、C₂D₆、C₃D₈、C₂D₄和C₂D₂上所引发的D⁻离子解吸结果。这些化合物以亚单层的量沉积在氪的多层固体薄膜以及无孔和多孔非晶冰的表面。虽然D⁻阴离子的解吸通过众所周知的过程进行，即解离电子附着（DEA）和偶极解离，但由于不同薄膜基底的存在，这些过程受到了显著干扰。我们已经表明，可以区分这些干扰的特征和性质。无孔冰的存在通过影响解离过程所经过的中间阴离子态的固有性质来干扰D⁻解吸强度。另一方面，多孔冰的存在引入了外在效应，这可能会影响电子在与烃分子相互作用之前的能量损失以及解离后碎片物种的能量和强度。文中提出并讨论了导致观察到的解吸阴离子信号强度变化的简单机制。从瞬态阴离子态到基底薄膜或附近烃分子的电子态的电子转移似乎是降低DEA过程幅度的最有效机制。
