School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom.
J Chem Phys. 2010 Aug 28;133(8):084302. doi: 10.1063/1.3469798.
Relative partial photoionization cross-sections and angular distribution parameters, beta, have been measured for the first, I(+)((3)P(2))<--I((2)P(3/2)), and fourth, I(+)((1)D(2))<--I((2)P(3/2)), (5p)(-1) photoelectron (PE) bands of atomic iodine, by performing angle-resolved constant-ionic-state (CIS) measurements on these PE bands in the photon energy range 11.0-23.0 eV. Three Rydberg series, two ns and one nd series, which converge to the I(+) (3)P(1) limit at 11.33 eV and four Rydberg series, two ns and two nd series, which converge to the I(+) (1)D(2) limit at 12.15 eV were observed in the first PE band CIS spectra. The fourth band CIS spectrum showed structure in the 12.9-14.1 eV photon energy range, which is also seen in the first band CIS spectra. This structure arises from excitation to ns and nd Rydberg states that are parts of series converging to the I(+) (1)S(0) limit we reported on earlier, as well as 5s-->5p excitations in the photon energy range 17.5-22.5 eV. These atomic iodine CIS spectra show reasonably good agreement with the equivalent spectra obtained for atomic bromine. The beta-plots for the first PE band recorded up to the I(+) (3)P(1) and I(+) (1)D(2) limits only show resonances corresponding to some of the 5p-->nd excitations observed in the first band CIS spectra scanned to the I(+) (1)D(2) limit (12.15 eV). These plots are interpreted in terms of an angular momentum transfer model with the positive values of beta obtained on resonances corresponding to parity allowed j(t)=1 and 3 channels and the off-resonance negative beta values corresponding to parity unfavored channels, where j(t) is the quantum number for angular momentum transfer between the molecule, and the ion and photoelectron. The beta-plots recorded for iodine are significantly different from those obtained for atomic bromine. Comparison of the experimental CIS spectra and beta-plots with available theoretical results highlights the need for higher level calculations which include factors such as configuration interaction in the initial and final states, relativistic effects including spin-orbit interaction, and autoionization via resonant Rydberg states.
已通过在 11.0-23.0 eV 的光子能量范围内对这些光电子带进行角度分辨的恒离化态（CIS）测量，首次测量了碘原子的第一，I(+)((3)P(2))<--I((2)P(3/2)) 和第四，I(+)((1)D(2))<--I((2)P(3/2))，(5p)(-1)光电子（PE）带的相对部分光电离截面和角分布参数β。在第一 PE 带 CIS 光谱中观察到三个 Rydberg 系列，两个 ns 和一个 nd 系列，它们在 11.33 eV 处收敛到 I(+) (3)P(1)极限，以及四个 Rydberg 系列，两个 ns 和两个 nd 系列，它们在 12.15 eV 处收敛到 I(+) (1)D(2)极限。在第一个 PE 带 CIS 光谱中观察到在 12.9-14.1 eV 光子能量范围内的结构，在第一个带 CIS 光谱中也观察到这种结构。这种结构源自 ns 和 nd Rydberg 态的激发，这些态是我们之前报道的收敛到 I(+) (1)S(0)极限的系列的一部分，以及在 17.5-22.5 eV 光子能量范围内的 5s-->5p 激发。这些碘原子 CIS 光谱与我们为溴原子获得的等效光谱相当吻合。记录的第一 PE 带的β图仅在记录到 I(+) (3)P(1)和 I(+) (1)D(2)极限时，仅显示与第一带 CIS 光谱扫描到 I(+) (1)D(2)极限（12.15 eV）时观察到的一些 5p-->nd 激发相对应的共振对应的β值。这些图是根据角动量转移模型解释的，其中获得的正β值对应于宇称允许的 j(t)=1 和 3 通道，而与非共振负β值对应于宇称不利的通道，其中 j(t) 是分子与离子和光电子之间角动量转移的量子数。记录的碘原子的β图与溴原子的β图有显著差异。将实验 CIS 光谱和β图与可用的理论结果进行比较，突出了需要进行更高水平的计算，包括初始和最终状态中的组态相互作用、相对论效应（包括自旋轨道相互作用）以及通过共振 Rydberg 态的自电离。
