以稀土和锕系为中心的重元素化学在材料、核能和环境科学中十分重要。但其理论研究因涉及复杂的电子强相关和显著的相对论效应（特别是多组态和旋-轨耦合效应），一直是化学科学中困难领域之一。长期以来重元素气态分子实验数据的缺乏阻碍着其理论的发展。本项目将采用申请团队新近发展的红外光解离谱学方法制备和表征一系列重要的稀土和锕系化合物，揭示其结构和成键的规律，并为理论计算提供准确可靠的实验参考数据；根据实验数据和最近发展的电子强相关理论，发展和验证精确可靠的适合稀土和锕系金属体系的计算方法， 理论计算将为重元素化合物的波谱、能谱归属及结构鉴定提供可靠的理论佐证。借助于理论与实验的紧密结合，阐明4f-5d/5f-6d电子、相对论效应和电子相关效应等对稀土和锕系化合物的分子结构、谱学性质、电子结构及成键规律和反应特性的影响。在结构化学前沿领域，发展重元素化学的光谱方法和成键理论模型，开展具有创新性的研究。

Heavy-element chemistry involving rare-earth (RE) and actinide (An) elements has played a significant role in materials, nuclear energy, and environmental science. However, theoretical studies on heavy-element compounds are difficult due to complicated strong electron correlation effects and significant relativistic effects, especially the multi-configurational and spin-orbit coupling effects. The lack of experimental data on the gaseous molecules of heavy-element compounds obstructs the validation of theoretical models. In this project, we will prepare and characterize a series of RE and An compounds using advanced Infrared Photodissociation Spectroscopy (IRPD) to reveal the structure and bonding features. The experimental work will provide accurate data for benchmarking theoretical models and validate the computational predictions. We will develop realistic theoretical models and approaches for heavy-element compounds, and improve computer algorithms for these systems. The theoretical investigations will provide confirmation and reliable interpretation of the experimental infrared, electronic spectra, photoelectron spectra, and electronic structures. Through this combined experimental and theoretical effort, we will elucidate the role played by 4f-5d/5f-6d electrons, relativistic effects, and electron correlation in the molecular structures, spectroscopic properties, electronic structures, and chemical bonding involving heavy-elements. The project aims at carrying out innovative, cutting-edge spectroscopic structural chemistry research in nuclear and rare-earth chemistry using state-of-the-art experimental and theoretical methods.