Bond Dissociation Energies and Electronic Structure of Small Transition Metal and Lanthanide Molecules

在化学系化学结构、动力学和机制-A（CSDM-A）项目的支持下，犹他州大学的Michael莫尔斯教授正在使用激光光谱学研究含有d-和f-区金属的小分子的电子结构和化学键合，重点是提供键离解和电离能的高度精确值。这些测量将是有用的，为更大的系统相关的d-和f-块元素的催化和技术应用开发准确和有效的计算方法。莫尔斯博士将研究化学键的广泛趋势，因为在这项工作中，一个移动的周期表，并将调查金属键合到化学相关的p-区元素，如硅和锗的离解能是否有很强的相关性。莫尔斯教授和他的学生将使用共振双光子电离光谱学研究中性d-和f-块分子，和低温冷却离子光解离实验研究含金属的阳离子。除了培训直接参与该项目的研究生外，莫尔斯博士还为高中化学教师组织了一年两次的研讨会，在那里他介绍了他们选择的物理化学主题。其他讲者亦会就化学教育研究及教育心理学发表演讲。在这个项目中，莫尔斯小组将利用激光烧蚀金属样品，使氦与少量反应气体发生脉冲超音速膨胀，以产生感兴趣物种的分子束。然后，他们将使用一个激光脉冲，这是扫描，以激发分子的电子和第二个激光脉冲，以激发分子。 然后使用飞行时间质谱法检测离子。具有高电子态密度的分子，例如开放的d-和f-亚壳层分子，当它们被激发到高于其解离能时，在亚纳秒时间尺度上分裂，导致离子信号急剧下降。这提供了对键能的高度精确的测量。莫尔斯团队还能够利用这些物种中的高密度电子态来高精度地测量电离能。使用不同的仪器，研究小组正在使用类似的方法来测量一系列d区和f区低温冷却离子的解离阈值。中性分子及其阳离子的键离解能然后可以与中性分子和金属原子的电离能结合使用热化学循环，以确认所有四个测量值的准确性。这些研究很可能是特别有用的密度泛函理论方法的发展，精确计算的分子含有d-和f-块elements.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Michael Morse of the University of Utah is using laser spectroscopy to study the electronic structure and chemical bonding in small molecules that contain d- and f-block metals, with emphasis on providing highly precise values of bond dissociation and ionization energies. These measurements will be useful for developing accurate and efficient computational methods for larger systems relevant to the catalytic and technological applications of the d- and f-block elements. Dr. Morse will examine the broad trends in chemical bonding as one moves across the periodic table in this work, and will investigate whether the dissociation energies of metals bonded to chemically related p-block elements, such as silicon and germanium, are strongly correlated. Professor Morse and his students will use resonant two-photon ionization spectroscopy to study neutral d- and f-block molecules, and cryo-cooled ion photodissociation experiments to study metal-containing cations. In addition to training the graduate students who are directly involved in this project, Dr. Morse also organizes a biannual workshop for high school chemistry teachers, where he presents on physical chemistry topics that they have selected. Other speakers also present on chemical education research and educational psychology.In this project, the Morse group will employ laser ablation of a metal sample in a pulsed supersonic expansion of helium with small amounts of a reactant gas to generate a molecular beam of the species of interest. They will then use a one laser pulse, which is scanned, to excite the molecule electronically and a second laser pulse to ionize the molecule. Ions will then be detected using time-of-flight mass spectrometry. Molecules with a high density of electronic states, such as the open d- and f-subshell molecules, fall apart on a subnanosecond time scale when they are excited above their dissociation energy, causing a sharp drop in ion signal. This provides a highly precise measurement of the bond energy. The Morse team is also able to use the high density of electronic states in these species to measure ionization energies to high precision. Employing a different instrument, the research team is using similar methods to measure the threshold for dissociation in a range of d- and f-block cryo-cooled ions. The bond dissociation energies of the neutral molecules and their cations can then be combined with the ionization energies of the neutral molecules and of the metal atoms using a thermochemical cycle to confirm the accuracy of all four measured values. These studies are likely to be particularly useful for the development of density functional theory methods for accurate computations of molecules containing the d- and f-block elements.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.