Non-Adiabatic Dynamics in Liquid Jets Studied by Time-Resolved XUV Photoelectronic Spectroscopy

通过时间分辨 XUV 光电光谱研究液体射流中的非绝热动力学

基本信息

批准号：
2154629
负责人：
Daniel Neumark
金额：
$ 38.28万
依托单位：
University of California-Berkeley
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2154629&HistoricalAwards=false
关键词：
Non Adiabatic Dynamics Liquid Jets

项目摘要

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Daniel Neumark and his research group at the University of California-Berkeley are carrying out experiments that probe the interaction of nucleic acid constituents with ultraviolet light. All nucleic acids have strong absorption bands in the ultraviolet at photon energies that are sufficient to dissociate these species into reactive free radicals, a process that would have significant negative biological consequences. However, electronic relaxation is known to compete with dissociation, rapidly channeling the electronically excited nucleic acids to their ground electronic states and releasing the excess energy harmlessly as heat. The team led by Prof. Neumark will perform novel time-resolved experiments to map out the pathways for electronic relaxation of nucleic acids in aqueous solution from the instant of photoexcitation to the ultimate production of ground state molecules, thus providing new insights into the electronic relaxation of these species. The results of these studies are not only of interest in fundamental chemical physics but also have potential impact in radiation chemistry and biology. The broader impacts of the project also include advanced training opportunities for students, including mentoring efforts that seek to enhance the advancement of female scientists and the recruitment of research students from groups that are underrepresented in science.Time-resolved photoelectron spectroscopy (TRPES) in liquid water microjets will be carried out in which solute molecules are excited with ultraviolet pump pulses and ionized using femtosecond extreme ultraviolet (XUV) pulses at 22 eV. These experiments probe the non-adiabatic relaxation dynamics of mono- and di-nucleotides subsequent to photoexcitation of their pi-pi* transitions around 4.7 eV. The energy of the 22 eV probe photons is sufficiently high to ionize these species not only in the initially excited states formed by UV excitation, but also in any electronic states that serve as intermediates in the overall relaxation mechanism as well as in the ground state. Hence, these experiments have the potential to provide a complete dynamical mapping of the electronic states that play a role in the relaxation of photoexcited mono- and di-nucleotides. Specifically, the research team will examine whether photoexcited nucleobases relax through optically dark states and also will probe the formation of transient exciplexes in photoexcited dinucleotides. A secondary goal of this project is to generate femtosecond pulses around 100 eV, a photon energy sufficient to eject core electrons from halogens and transition metals. Initial steps toward this capability will be undertaken during the current grant period toward the longer-term goal of enabling transformative new measurements of the excited-state dynamics of solvated molecules using core ionization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在化学结构，动力学和机制-A（CSDM-A）计划的支持下，丹尼尔·诺伊克（Daniel Neumark）教授及其加州大学 - 伯克利分校的研究小组正在进行探测核酸组成量与紫外线的相互作用的实验。所有核酸在光子能量的紫外线中均具有强吸收带，足以将这些物种分离为反应性自由基，这一过程将具有显着的负面生物学后果。然而，已知电子弛豫与解离竞争，将电子激发的核酸迅速传递到其地面电子状态，并随着热量无害释放多余的能量。由Neumark教授领导的团队将执行新颖的时间分辨实验，以绘制从光激发的瞬间到基态分子的最终产生的水溶液中核酸的电子弛豫的途径，从而为这些物种的电子松弛提供了新的见解。这些研究的结果不仅对基本化学物理学感兴趣，而且对放射化学和生物学产生了潜在的影响。 The broader impacts of the project also include advanced training opportunities for students, including mentoring efforts that seek to enhance the advancement of female scientists and the recruitment of research students from groups that are underrepresented in science.Time-resolved photoelectron spectroscopy (TRPES) in liquid water microjets will be carried out in which solute molecules are excited with ultraviolet pump pulses and ionized using femtosecond extreme ultraviolet （XUV）22 eV的脉冲。这些实验探测了在4.7 eV左右的PI-PI*转变后，单核苷酸和二核苷酸的非绝热弛豫动力学。 22 eV探针光子的能量足够高，不仅在紫外线激发形成的最初激发态中，而且在任何作为整体弛豫机制中的中间体以及基态中的中间体中的任何电子状态都将这些物种电离。因此，这些实验具有对电子状态的完整动力学映射的潜力，这些映射在光激发单核苷酸和二核苷酸的放松中起作用。具体而言，研究小组将检查光激发核碱是否通过光学黑色状态放松，并且还将探测光激发二核苷酸中的瞬时分离。该项目的次要目标是生成大约100 eV的飞秒脉冲，这是一种足以从卤素和过渡金属中驱射核心电子的光子能量。将在当前赠款期间实现朝着这种能力的初步步骤，以实现长期目标，即使用核心电离实现溶剂化分子激发的动态的变革性新测量。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子和更广泛的影响来评估NSF的法定任务，并被认为是值得的。