Structure and Bonding in Double Rydberg Anions and Related Species

双里德伯阴离子和相关物种的结构和键合

• 批准号: 1565760
• 负责人: Joseph Ortiz
• 金额: $ 42万
• 依托单位: Auburn University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1565760&HistoricalAwards=false
• 关键词: Structure; Bonding; Double; Rydberg; Anions

J. V. (Vince) Ortiz of Auburn University is supported by an award from the Chemical Theory, Models and Computational program in the Chemistry division to develop and apply computational approaches based on quantum mechanics to study an unusual type of molecular ion, known as double Rydberg anions (DRAS). At an early stage in their education, students of chemistry learn the importance of pairs of negatively charged electrons in understanding chemical bonding. In two familiar types of electron pairs, those involved in chemical bonding between atoms and those that are confined in a non-bonding fashion to a single atom, the electron pairs are called "valence electrons" because they can be found relatively close to the atomic nucleus. In quantum mechanics, these electrons are described by interference between atomic-orbital waves. Recent experiments and calculations have shown that positively charged molecular ions are capable of binding two electrons with diffuse orbital waves in species known as double Rydberg anions (DRAs). A new kind of electron pair in which the electrons may be found further from the atomic nucleus occurs in DRAs, for example, NH4-, a positively charged ammonium cation with two diffuse weakly bound electrons. Ortiz and his research group develop and use sophisticated theoretical and computational methods to predict the existence of new DRAs and related species and to understand the interactions between electrons which permit DRAs to exist. Educational activities that are coordinated with this research are directed toward students and scientists with a variety of cultural experiences and academic backgrounds. New, fundamental concepts in chemical bonding will be integrated immediately into educational and outreach activities and will enable students and scientists to predict and understand a greater variety of chemical phenomena. To gain a better understanding of the electron correlation between two diffuse electrons that is essential for the formation of double Rydberg anions, transition amplitudes that connect states of these anions to those of uncharged radicals or closed-shell cations are analyzed. These amplitudes, known as Dyson orbitals and Dyson geminals, are generated in electron propagator and two-electron propagator calculations of electron binding energies. The effects of hydrogen bonds and of chemical substitutions on the structure and stability of the double Rydberg anions are explored and the photoelectron spectra of larger double Rydberg anions are being assigned. Correlation states in these photoelectron spectra which correspond to excited states of uncharged, Rydberg radicals also are also being assigned and predicted. Potential generalizations of the double Rydberg concept to anions with atoms of the fourth through sixth periods are based on closed-shell configurations of united-atom limits and isoelectronic relationships. Experimentalists who synthesize, isolate and characterize molecular anions in the gas phase are or will be provided reliable predictions on the stability and spectral properties of species with unprecedented patterns of electronic structure. Deeper insight into chemical bonding in double Rydberg anions will follow from an analysis of Dyson orbitals and geminals that connect these ions to Rydberg radicals and their cationic cores. Novel theoretical and computational techniques that are adapted to the search for such species will be published for the benefit of those who develop ab initio methodology. Ortiz continues his many efforts to recruit, educate and promote female and minority scientists. Among these activities are the training of graduate students, seminars and short courses, lectures to student and professional groups, popularizations for secondary-school students, scientific conferences, exchange programs, and organizational efforts for minority students and professionals. Students and young professionals are exposed to highly novel patterns of chemical bonding that alter the paradigms encountered in basic chemistry courses.

奥本大学的J. V.（Vince）Ortiz获得了化学系化学理论、模型和计算项目的一项奖励，以开发和应用基于量子力学的计算方法来研究一种不寻常的分子离子，称为双里德伯阴离子（DRAS）。在教育的早期阶段，化学专业的学生学习带负电荷的电子对理解化学键的重要性。 在两种熟悉的电子对中，那些参与原子之间的化学键合的电子对和那些以非键合方式被限制在单个原子上的电子对，这些电子对被称为“价电子”，因为它们可以相对接近原子核。在量子力学中，这些电子被描述为原子轨道波之间的干涉。 最近的实验和计算表明，带正电荷的分子离子能够结合两个电子与扩散轨道波的物种称为双里德伯阴离子（DRA）。 一种新的电子对，其中的电子可能会被发现远离原子核出现在DRA中，例如，NH 4-，一个带正电荷的铵阳离子与两个扩散的弱束缚电子。 Ortiz和他的研究小组开发并使用复杂的理论和计算方法来预测新DRA和相关物种的存在，并了解允许DRA存在的电子之间的相互作用。 与这项研究相协调的教育活动是针对具有各种文化经验和学术背景的学生和科学家的。化学键的新的基本概念将立即纳入教育和推广活动，使学生和科学家能够预测和理解更多种类的化学现象。为了更好地了解两个扩散电子之间的电子相关性，这是必不可少的双里德堡阴离子的形成，过渡振幅，这些阴离子的不带电的自由基或闭壳层阳离子的连接状态进行了分析。这些振幅被称为戴森轨道和戴森孪子，是在电子传播子和双电子传播子计算电子结合能时产生的。探讨了氢键和化学取代对双里德伯阴离子结构和稳定性的影响，并对较大的双里德伯阴离子的光电子能谱进行了归属。 在这些光电子光谱中对应于不带电的激发态的相关态，Rydberg自由基也被分配和预测。 双里德伯概念对第四至第六周期原子的阴离子的潜在推广是基于联合原子极限和等电子关系的闭壳层构型。 合成、分离和表征气相分子阴离子的实验学家正在或将获得关于具有前所未有的电子结构模式的物种的稳定性和光谱特性的可靠预测。 更深入地了解化学键在双里德伯阴离子将遵循从戴森轨道和双子连接这些离子的里德伯自由基和它们的阳离子核心的分析。 新的理论和计算技术，适用于搜索这些物种将出版的利益，那些谁开发从头算方法。 奥尔蒂斯继续他的许多努力，招募，教育和促进女性和少数民族科学家。 这些活动包括研究生培训、研讨会和短期课程、学生和专业团体讲座、中学生普及活动、科学会议、交流方案以及少数民族学生和专业人员的组织工作。 学生和年轻的专业人士接触到改变基础化学课程中遇到的范式的化学键合的高度新颖的模式。