Lias S G, Ausloos P
Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.
J Res Natl Bur Stand A Phys Chem. 1971 Nov-Dec;75A(6):591-605. doi: 10.6028/jres.075A.048.
Ions of the formula have been generated with different initial energies by ionizing ethylene ( , where the ion is formed with an initial energy of > 11.51 eV), cyclobutane (initial energy of , > 10.84 eV), methylcyclopropane (> 10.15 eV), 1-CH (> 9.58 eV), and -CH (> 9.06 eV) with 11.6-11.8 eV photons, and in some cases also with 10 eV photons and with gamma radiation. The structures of the ions have been determined from the structures of the CH products formed in charge transfer reaction between the ions and charge acceptors such as dimethylamine and nitric oxide, as well as from the structures of the butanes formed in transfer reactions with methylcyclopentane- ( ). At low pressures the ions initially formed in ethylene, cyclobutane, and methylcyclopropane isomerize to the thermodynamically most stable configurations, and . The structure predominates in all the experiments. As the pressure is raised, the ion yield diminishes as that of increases, indicating that when the precursor of the ion is collisionally deactivated, it ends up as . At high pressures, ions are intercepted; their yield increases with increasing pressure, indicating that is an intermediate which isomerizes further unless it is collisionally deactivated. The ion formed in methylcyclopropane (initial energy > 10.15 eV) is more easily deactivated than that formed in cyclobutane (initial energy > 10.84 eV). That the isomerization of the ion to lower energy structures such as and requires excess internal energy is demonstrated by the fact that in the photolysis with 10 eV photons, a negligible amount of isomerization is observed, but with 11.6-11.8 eV photons, more than half of the ions isomerize to the structure at a pressure of 2 torr. Isomerization of the low energy ions formed in the photolysis of -CH to other structures is relatively unimportant at 11.6-11.8 eV. Taking the ratio as an indicator of the amount of energy removed by collisions from the intermediate species under conditions where only and ions are intercepted, it is shown that the efficiency of energy transfer from the ions to helium, hydrogen, neon, krypton, xenon, nitrogen, and carbon dioxide is related to the polarizability of the added deactivator.
通过用11.6 - 11.8 eV光子电离乙烯（ ，其中 离子形成时的初始能量> 11.51 eV）、环丁烷（初始能量 ，> 10.84 eV）、甲基环丙烷（> 10.15 eV）、1 - CH（> 9.58 eV）和 - CH（> 9.06 eV），在某些情况下还用10 eV光子和γ辐射，已产生了具有不同初始能量的通式为 的离子。离子的结构已根据离子与电荷受体如二甲胺和一氧化氮之间的电荷转移反应中形成的CH产物的结构，以及与甲基环戊烷 - （ ）的 转移反应中形成的丁烷的结构来确定。在低压下，最初在乙烯、环丁烷和甲基环丙烷中形成的 离子异构化为热力学上最稳定的构型 和 。在所有实验中 结构占主导。随着压力升高， 离子产率降低而 的产率增加，这表明当 离子的前体通过碰撞失活时，最终会变成 。在高压下， 离子被截获；它们的产率随压力增加而增加，表明 是一种中间体，除非通过碰撞失活，否则会进一步异构化。在甲基环丙烷（初始能量> 10.15 eV）中形成的 离子比在环丁烷（初始能量> 10.84 eV）中形成的 离子更容易失活。 离子异构化为能量较低的结构如 和 需要过量的内能，这一事实由以下现象证明：在10 eV光子的光解中，观察到的异构化量可忽略不计，但在11.6 - 11.8 eV光子作用下，在2托的压力下，超过一半的 离子异构化为 结构。在11.6 - 11.8 eV下， - CH光解中形成的低能量 离子异构化为其他结构相对不太重要。以 比值作为在仅截获 和 离子的条件下，碰撞从中间 物种去除的能量量的指标，结果表明离子向氦、氢、氖、氪、氙、氮和二氧化碳的能量转移效率与添加的失活剂的极化率有关。
