Department of Chemistry, National University of Ireland Maynooth , Maynooth, Co. Kildare, Ireland.
J Phys Chem A. 2013 Sep 26;117(38):9168-78. doi: 10.1021/jp404695a. Epub 2013 Sep 13.
Optical absorption spectra of thin film samples, formed by the codeposition of zinc vapor with D2 and CH4, have been recorded with synchrotron radiation. With sufficiently low metal vapor flux, samples deposited at 4 K were found to consist exclusively of isolated zinc atoms for both solids. The atomic absorption bands in the quantum solids D2 and CH4 were found to exhibit large bandwidths, behavior related to the high lattice frequencies of these low mass solids. The reactivity of atomic zinc was promoted with (1)P state photolysis leading to the first recording of electronic absorption spectra for the molecules ZnD2 and CH3ZnH in the vacuum ultraviolet (VUV) region. (3)P state luminescence of atomic zinc observed in the Zn/CH4 system points to the involvement of the spin triplet state in the relaxation of CH3ZnH system as it evolves into the C3v ground state. This state is not involved in the relaxation of the higher symmetry molecule ZnD2. Time dependent density functional theory (TD-DFT) calculations were conducted to predict the electronic transitions of the inserted molecular species. Comparisons with experimental data indicate the predicted transition energies are approximately 0.5 eV less than the recorded values. Possible reasons for the discrepancy are discussed. The molecular photochemistry of ZnD2 and CH3ZnH observed in the VUV was modeled successfully with a simple four-valence electron AH2 Walsh-type diagram.
利用同步辐射，记录了由锌蒸气与 D2 和 CH4 共沉积形成的薄膜样品的光学吸收光谱。在足够低的金属蒸气通量下，对于两种固体，在 4 K 下沉积的样品被发现仅由孤立的锌原子组成。在量子固体 D2 和 CH4 中的原子吸收带表现出大的带宽，这种行为与这些低质量固体的高晶格频率有关。原子锌的反应性通过（1）P 态光解促进，从而首次在真空紫外（VUV）区域记录了分子 ZnD2 和 CH3ZnH 的电子吸收光谱。在 Zn/CH4 体系中观察到的原子锌的（3）P 态发光表明，在 CH3ZnH 体系弛豫过程中涉及到自旋三重态，因为它演变成 C3v 基态。这种状态不涉及对称性更高的分子 ZnD2 的弛豫。进行了时间依赖的密度泛函理论（TD-DFT）计算，以预测插入分子物种的电子跃迁。与实验数据的比较表明，预测的跃迁能量比记录的值约低 0.5 eV。讨论了产生差异的可能原因。ZnD2 和 CH3ZnH 的分子光化学在 VUV 中被成功地用简单的四价电子 AH2 Walsh 型图进行了建模。
