Relaxation Dynamics of Hydrated Thymine, Thymidine, and Thymidine Monophosphate Probed by Liquid Jet Time-Resolved Photoelectron Spectroscopy
Relaxation Dynamics of Hydrated Thymine, Thymidine, and Thymidine Monophosphate Probed by Liquid Jet Time-Resolved Photoelectron Spectroscopy
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DOI：
10.1021/acs.jpca.9b08258
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发表时间：
2019-12-19
影响因子：
2.9
通讯作者：
Neumark, Daniel M.
中科院分区：
文献类型：
--
作者：
Erickson, Blake A.;Heim, Zachary N.;Neumark, Daniel M.
利用时间分辨光电子能谱技术研究了胸腺嘧啶及其衍生物胸腺嘧啶和单磷酸胸腺嘧啶的弛豫动力学。研究了两个吸收带；第一种是明亮的pi pi*状态，使用范围为4.74-5.17 eV的可调紫外光填充，并使用6.20 eV的探测脉冲进行探测。通过反转这些脉冲的顺序，包含多个π π *状态的带被6.20 eV脉冲填充，低能量脉冲作为探针。在胸腺嘧啶和胸腺嘧啶中，较低的pi pi*态的衰减与泵浦光子能量无关，其衰减时间与400 fs相似，而单磷酸胸腺嘧啶的衰减时间在670 ~ 840 fs之间，与泵浦能量有关。计算量子力学/分子力学方案在XMS-CASPT2//CASSCF/AMBER理论水平上的应用表明，胸腺嘧啶和单磷酸胸腺嘧啶在溶液中存在的构象差异可以解释这种差异。发现在所有三种情况下，较高的pi pi*带的衰减速度与600 fs相似，但只有在使用5.17 eV探针脉冲时才能表征。值得注意的是，在这三个分子的任何一个实验中，都无法识别出来自n π *态的长寿命信号。
The relaxation dynamics of thymine and its derivatives thymidine and thymidine monophosphate are studied using time-resolved photoelectron spectroscopy applied to a water microjet. Two absorption bands are studied; the first is a bright pi pi* state which is populated using tunable-ultraviolet light in the range 4.74-5.17 eV and probed using a 6.20 eV probe pulse. By reversing the order of these pulses, a band containing multiple pi pi* states is populated by the 6.20 eV pulse and the lower energy pulse serves as the probe. The lower lying pi pi* state is found to decay in similar to 400 fs in both thymine and thymidine independent of pump photon energy, while thymidine monophosphate decays vary from 670 to 840 fs with some pump energy dependence. The application of a computational quantum mechanical/molecular mechanical scheme at the XMS-CASPT2//CASSCF/AMBER level of theory suggests that conformational differences existing between thymidine and thymidine monophosphate in solution account for this difference. The higher lying pi pi* band is found to decay in similar to 600 fs in all three cases, but it is only able to be characterized when the 5.17 eV probe pulse is used. Notably, no long-lived signal from an n pi* state can be identified in either experiment on any of the three molecules.