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首页> 外文期刊>The Journal of Chemical Physics >Photoexcitation of iodide ion-pyrimidine clusters above the electron detachment threshold: Intracluster electron transfer versus nucleobase-centred excitations
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Photoexcitation of iodide ion-pyrimidine clusters above the electron detachment threshold: Intracluster electron transfer versus nucleobase-centred excitations

机译：电子脱离阈值高于电子脱离阈值的碘化物离子嘧啶簇的光筛：颅内电子转移与核碱基含量为中心的激励

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Laser photodissociation spectroscopy of the I-center dot thymine (I-center dot T) and I-center dot cytosine (I-center dot C) nucleobase clusters has been conducted for the first time across the regions above the electron detachment thresholds to explore the excited states and photodissociation channels. Although photodepletion is strong, only weak ionic photofragment signals are observed, indicating that the clusters decay predominantly by electron detachment. The photodepletion spectra of the I-center dot T and I-center dot C clusters display a prominent dipole-bound excited state (I) in the vicinity of the vertical detachment energy(similar to 4.0 eV). Like the previously studied I-center dot uracil (I-center dot U) cluster [W. L. Li et al., J. Chem. Phys. 145, 044319 (2016)], the I-center dot T cluster also displays a second excited state (II) centred at 4.8 eV, which we similarly assign to a pi-pi* nucleobase-localized transition. However, no distinct higher-energy absorption bands are evident in the spectra of the I-center dot C. Time-dependent density functional theory (TDDFT) calculations are presented, showing that while each of the I-center dot T and I-center dot U clusters displays a single dominant pi-pi* nucleobase-localized transition, the corresponding pi-pi* nucleobase transitions for I-center dot C are split across three separate weaker electronic excitations. I- and deprotonated nucleobase anion photofragments are observed upon photoexcitation of both I-center dot U and I-center dot T, with the action spectra showing bands (at 4.0 and 4.8 eV) for both the I- and deprotonated nucleobase anion production. The photofragmentation behaviour of the I-center dot C cluster is distinctive as its I(-)photofragment displays a relatively flat profile above the expected vertical detachment energy. We discuss the observed photofragmentation profiles of the I-center dot pyrimidine clusters, in the context of the previous time-resolved measurements, and conclude th
机译：的I-中心点胸腺嘧啶的激光光解光谱（I-中心点T）和I-中心点胞嘧啶（I-中心点C）的核碱基簇已经首次上方的电子脱离阈值探索已经进行各区域激发态和光解渠道。虽然photodepletion强，只有弱离子光碎片信号被观察到，这表明由簇电子脱离主要衰减。的I-中心点T和I-中心点C个群集中的photodepletion光谱显示在垂直剥离用能量（类似于4.0eV）的附近的突出偶极结合的激发态（I）。像先前研究的I-中心点尿嘧啶（I-中心点U）簇[W. L. Li等人。，J。化学式物理。 145，044319（2016）]中，I-中心点T-簇还显示在为4.8eV为中心的第二激发态（II），这是我们类似地分配给的π-π*核碱基本地化过渡。然而，没有明显的高能量吸收带中的I-中心点C.时间依赖密度泛函理论的光谱明显的（TDDFT）的计算被呈现，显示出而每个I-中心点T和I-中心的点ü簇显示单个显性π-π*核碱基本地化过渡，相应的π-π*跃迁的核碱基为I-中心点C是在三个单独的较弱的电子激发分裂。 I-和去质子化的核碱基阴离子photofragments是对双方I-中心点U和I-中心点的T激发观察到的，与示出带的作用光谱（在4.0和4.8电子伏特），用于两个I-和去质子化的核碱基阴离子产生。的I-中心C点簇的光碎片化行为是显着特征，它的I（ - ）光碎片显示预期垂直剥离用能量以上的相对平坦的轮廓。我们讨论了I-中心点嘧啶集群的观测光碎片化配置文件，在之前的时间分辨测量的情况下，并得出结论日

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