Quantum chemical methods for studying photon and electron-driven processes

天普大学的Spiridoula Matsika获得了化学学部化学理论、模型和计算方法项目的奖励，以开发和应用理论方法来更好地理解电子驱动过程。电子在自然界中无处不在。电子与原子和分子的碰撞在生物学、化学和技术中都是必不可少的。电子驱动现象的例子可以在星际化学、辐射化学、环境化学、废物储存库的稳定性、微电子设备材料的等离子体处理和其他应用中找到。电子驱动过程的一个主要复杂之处在于，所涉及的状态是亚稳定的，因为它们可以通过一个被称为自脱离的过程失去电子。Matsika和她的研究小组开发了量子力学方法来治疗电子驱动过程中的亚稳态及其行为。他们运用这些方法来更好地了解辐射对DNA的损害。低能电子可以导致DNA链断裂，因此低能电子与DNA的相互作用是非常重要的。本研究将由一个由本科生、研究生和博士后组成的研究小组进行。电子驱动过程与光引发过程有几个相似之处，Matsika小组和其他人在后一个领域取得的进展可以用来增强前一个过程中可用的工具。在光激发现象和电子驱动现象中都产生了远离平衡态和短寿命的电子激发态。在这两种情况下，非绝热事件是至关重要的，锥形相交是规则而不是豁免。本工作的具体目标是：1)建立高效的亚稳态多参考构型相互作用（MRCI）方法。复合吸收电位（CAP）方法与MRCI方法相结合，得到了这些态的能量和寿命。结合传统的MRCI方法和CAP/MRCI方法，研究了与共振相关的势能面、锥形交叉点和非绝热事件。2)利用第(1)部分开发的方法对核碱基的解离电子附着（DEA）进行理论研究。为了解决核碱基中的DEA，首先确定共振，然后探索导致DEA的途径和实验观察到的产物。所开发的方法将在可公开获得的计算软件中实施。

Spiridoula Matsika of Temple University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to develop and apply theoretical methods to better understand electron-driven processes. Electrons are ubiquitous in nature. Collisions of electrons with atoms and molecules are essential in biology and chemistry, as well as in technology. Examples of electron-driven phenomena can be found in interstellar chemistry, radiation chemistry, environmental chemistry, stability of waste repositories, plasma processing of materials for microelectronic devices and other applications. A major complication in electron-driven processes is that the in that the states that are involved are meta-stable since they can lose the electron via a process known as autodetachment. Matsika and her research group develop quantum mechanical approaches to treat metastable states and their behavior in electron-driven processes. They apply these methods to better understand DNA damage by radiation.. Low energy electrons can cause DNA strands to break and thus the interaction of low energy electrons with DNA is of major importance. This research will be carried out by a research team involving collaboration of undergraduate and graduate students with postdoctoral associates.Electron-driven processes have several similarities to photo-initiated processes, and progress made by the Matsika group and others in the latter field can be used to enhance the tools available in the former processes. In both photo-initiated and electron-driven phenomena electronically excited states are generated which are far from equilibrium and short lived. Nonadiabatic events are crucial and conical intersections are the rule rather than the exemption in both cases. Specific goals of this work are: 1) Development of efficient multireference configuration interaction (MRCI) methods for metastable states. The complex absorbing potential (CAP) approach is used in combination with MRCI to obtain both the energies and lifetimes of these states. A combination of conventional MRCI methods and CAP/MRCI are used to study potential energy surfaces, conical intersections, and nonadiabatic events related to resonances. 2) Theoretical studies of dissociative electron attachment (DEA) in nucleobases using the approaches developed in part (1). In order to address DEA in nucleobases the resonances are identified first, followed by explorations of the pathways leading to DEA and the experimentally observed products. The methodology developed will be implemented in publicly available computational software.