Ionization of the I 3d, 4s, and 4p orbitals in methyl iodide (CH₃I) has been studied by using synchrotron radiation to measure the total ion yield and by recording photoelectron spectra with linearly polarized radiation in two polarization orientations. The complete photoelectron spectrum of CH₃I has been recorded at several photon energies, and bands due to the C 1s, I 3d, 4s, 4p, and 4d atomic-like orbitals, as well as the molecular orbitals, have been observed and assigned. In the vicinity of the I 3d_5/2 and 3d_3/2 ionization thresholds at 626.8 and 638.3 eV, respectively, the ion yield displays weak structure in the pre-edge region due to transitions into valence or Rydberg states, and, at higher energies, a shoulder and a broad maximum attributed to the I 3d_5/2 → εf and the I 3d_3/2 → εf shape resonances, respectively. The absorption spectrum calculated using time-dependent density functional theory, within the Tamm-Dancoff approximation, has allowed assignments to be proposed for the valence and Rydberg states. The Stieltjes imaging technique has been used to simulate the absorption spectrum above the ionization threshold and indicates that transitions into the f(l = 3) continuum channel dominate. This conclusion has been corroborated by a Continuum Multiple Scattering–Xα (CMS–Xα) calculation. The asymmetric broadening of the photoelectron bands associated with the I 3d orbital, due to post collision interaction, is taken into account in our experimental analysis. Experimentally derived photoelectron anisotropy parameters for the I 3d orbital are in good agreement with the theoretical predictions obtained with the CMS–Xα approach. The I 3d shake-up/shake-off photoelectron spectrum has been recorded, and assignments have been proposed for several of the satellites. The M₄N₄₅N₄₅ and M₅N₄₅N₄₅ Auger electron yields have been measured, and that for the M₅N₄₅N₄₅ decay exhibits a maximum due to interchannel coupling between the 3d_5/2 and 3d_3/2 continua. The photoelectron band associated with the I 4p orbital has an unusual appearance. Based upon previous theoretical work for the analogous Xe 4p orbital, it appears that the initial I 4p⁻¹ hole state decays rapidly through Coster-Kronig and super-Coster-Kronig transitions. This leads to a redistribution of the spectral intensity associated with the I 4p orbital and results in a photoelectron spectrum containing a single structured band together with an extended continuum. Another continuum is observed on the high binding energy side of the peak due to the 4s orbital, and we assign this to super-Coster-Kronig transitions into the 4p^-14d⁻¹ continuum.

中文翻译：

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碘甲烷中碘3d，4s和4p轨道的光电离

通过使用同步加速器辐射测量总离子收率并通过记录线性极化辐射在两个偏振方向上的光电子能谱，研究了碘甲烷（CH ₃ I）中I 3d，4s和4p轨道的电离。已在几种光子能量下记录了CH ₃ I的完整光电子能谱，并观察到并归因于C 1s，I 3d，4s，4p和4d原子状轨道以及分子轨道而产生的能带。在I 3d _5/2和3d _3/2附近电离阈值分别为626.8和638.3 eV，由于过渡到化合价或Rydberg态，离子收率在前缘区域显示出较弱的结构，并且在较高的能量下，肩峰和宽的最大值归因于I 3d _{5 / 2} → εf和I 3d _3/2 → εf分别形成共振。在Tamm-Dancoff近似内，使用时变密度泛函理论计算的吸收光谱已允许为价态和Rydberg态提出分配。Stieltjes成像技术已被用于模拟高于电离阈值的吸收光谱，并表明过渡到f（l= 3）连续通道占主导地位。连续多次散射-Xα（CMS-Xα）计算结果证实了这一结论。在我们的实验分析中，考虑到由于碰撞后相互作用，与I 3d轨道相关的光电子能带的不对称展宽。实验得出的I 3d轨道的光电子各向异性参数与CMS–Xα方法获得的理论预测非常吻合。记录了I 3d摇动/摇动光电子谱，并已为若干颗卫星提出了分配方案。M ₄ N ₄₅ N ₄₅和M ₅ N ₄₅ N ₄₅已经测量了俄歇电子产额，并且由于3d _5/2和3d _3/2连续区之间的通道间耦合，M ₅ N ₄₅ N _45的衰变表现出最大值。与I 4p轨道相关的光电子带具有异常的外观。根据先前对类似Xe 4p轨道的理论工作，似乎初始I 4p ^-1空穴状态通过Coster-Kronig和super-Coster-Kronig跃迁迅速衰减。这导致与I 4p轨道相关的光谱强度的重新分布，并导致包含单个结构化谱带和扩展连续谱的光电子谱。另一个连续体上的峰的高结合能侧观察到由于轨道的4S，我们分配这对超科斯特-克勒尼希过渡到4P ^-1 4D ^-1连续统一体。