Herman Zdenek
V. Cermák Laboratory, J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
J Am Soc Mass Spectrom. 2003 Dec;14(12):1360-72. doi: 10.1016/j.jasms.2003.09.002.
Surface-induced dissociation (SID) and reactions following impact of well-defined ion beams of polyatomic cations C2H5OH+, CH4+, and CH5+ (and its deuterated variants) at several incident angles and energies with self-assembled monolayers (SAM), carbon surfaces, and hydrocarbon covered stainless steel were investigated by the scattering method. Energy transfer and partitioning of the incident projectile energy into internal excitation of the projectile, translational energy of products, and energy transferred into the surface were deduced from the mass spectra and the translational energy and angular distributions of the product ions. Conversion of ion impact energy into internal energy of the recoiling ions peaked at about 17% of the incident energy for the perfluoro-hydrocarbon SAM, and at about 6% for the other surfaces investigated. Ion survival probability is about 30-50 times higher for closed-shell ions than for open-shell radical cations (e.g., 12% for CD5+ versus 0.3% for CD4+, at the incident angle of 60 degrees with respect to the surface normal). Contour velocity plots for inelastic scattering of CD5+ from hydrocarbon-coated and hydrocarbon-free highly oriented pyrolytic graphite (HOPG) surfaces gave effective masses of the surface involved in the scattering event, approximately matching that of an ethyl group (or two methyl groups) and four to five carbon atoms, respectively. Internal energy effects in impacting ions on SID were investigated by comparing collision energy resolved mass spectra (CERMS) of methane ions generated in a low pressure Nier-type electron impact source versus those generated in a Colutron source in which ions undergo many collisions prior to extraction and are essentially vibrationally relaxed. This comparison supports the hypothesis that internal energy of incident projectile ions is fully available to drive their dissociation following surface impact.
通过散射方法研究了表面诱导解离（SID）以及多原子阳离子C2H5OH+、CH4+和CH5+（及其氘代变体）在几个入射角和能量下与自组装单分子层（SAM）、碳表面和碳氢化合物覆盖的不锈钢发生碰撞后的反应。从质谱以及产物离子的平动能和角分布中推导出入射弹丸能量的转移和分配情况，即入射弹丸能量在弹丸内部激发、产物平动能以及转移到表面的能量之间的分配。对于全氟碳氢化合物SAM，离子碰撞能量转化为反冲离子内能的比例在入射能量的约17%时达到峰值，而对于其他所研究的表面，该比例约为6%。闭壳层离子的离子存活概率比开壳层自由基阳离子高约30 - 50倍（例如，相对于表面法线成60度入射角时，CD5+的离子存活概率为12%，而CD4+为0.3%）。CD5+从涂覆碳氢化合物和未涂覆碳氢化合物的高度取向热解石墨（HOPG）表面发生非弹性散射的等高线速度图给出了参与散射事件的表面有效质量，分别约与一个乙基（或两个甲基）和四到五个碳原子的有效质量相匹配。通过比较在低压尼尔型电子碰撞源中产生的甲烷离子与在科鲁特龙源中产生的甲烷离子的碰撞能量分辨质谱（CERMS），研究了碰撞离子的内能对表面诱导解离的影响。在科鲁特龙源中，离子在提取之前会经历多次碰撞，并且基本上处于振动弛豫状态。这种比较支持了这样的假设，即入射弹丸离子的内能在表面碰撞后可完全用于驱动其解离。
