School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
J Phys Chem A. 2011 Jun 16;115(23):5936-42. doi: 10.1021/jp110332v. Epub 2011 May 6.
The interaction and autoionization of HCl on low-temperature (80-140 K) water ice surfaces has been studied using low-energy (5-250 eV) electron-stimulated desorption (ESD) and temperature programmed desorption (TPD). There is a reduction of H(+) and H(2)(+) and a concomitant increase in H(+)(H(2)O)(n=1-7) ESD yields due to the presence of submonolayer quantities of HCl. These changes are consistent with HCl induced reduction of dangling bonds required for H(+) and H(2)(+) ESD and increased hole localization necessary for H(+)(H(2)O)(n=1-7) ESD. For low coverages, this can involve nonactivated autoionization of HCl, even at temperatures as low as 80 K; well below those typical of polar stratospheric cloud particles. The uptake and autoionization of HCl is supported by TPD studies which show that for HCl doses ≤0.5 ± 0.2 ML (ML = monolayer) at 110 K, desorption of HCl begins at 115 K and peaks at 180 K. The former is associated with adsorption of a small amount of molecular HCl and is strongly dependent on the annealing history of the ice. The latter peak at 180 K is commensurate with desorption of HCl via recombinative desorption of solvated separated ion pairs. The activation energy for second-order desorption of HCl initially in the ionized state is 43 ± 2 kJ/mol. This is close to the zero-order activation energy for ice desorption.
HCl 在低温（80-140 K）水冰表面上的相互作用和自电离已通过低能（5-250 eV）电子刺激解吸（ESD）和程序升温解吸（TPD）进行了研究。由于存在亚单层量的 HCl，H(+)和 H(2)(+) 的产生减少，并且 H(+)(H(2)O)(n=1-7) ESD 产率相应增加。这些变化与 HCl 诱导悬空键减少有关，这是 H(+)和 H(2)(+) ESD 所需的，并且为 H(+)(H(2)O)(n=1-7) ESD 所需的空穴定位增加。对于低覆盖率，这甚至可以涉及非活化的 HCl 自电离，即使在低至 80 K 的温度下；远低于典型的极性平流层云粒子的温度。HCl 的吸收和自电离得到 TPD 研究的支持，该研究表明对于 110 K 时的 HCl 剂量≤0.5±0.2 ML（ML=单层），HCl 的解吸始于 115 K 并在 180 K 处达到峰值。前者与少量分子 HCl 的吸附有关，并且强烈依赖于冰的退火历史。后者在 180 K 处的峰值与通过溶剂化分离的离子对的重组解吸而通过解吸的 HCl 相对应。初始处于离子化状态的 HCl 的二级解吸的活化能最初为 43±2 kJ/mol。这接近于冰解吸的零级活化能。
