Atomic and Molecular Physics Division, Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138.
Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 8410501, Israel.
Proc Natl Acad Sci U S A. 2023 Jul 11;120(28):e2303586120. doi: 10.1073/pnas.2303586120. Epub 2023 Jul 3.
The unique optical cycling efficiency of alkaline earth metal-ligand molecules has enabled significant advances in polyatomic laser cooling and trapping. Rotational spectroscopy is an ideal tool for probing the molecular properties that underpin optical cycling, thereby elucidating the design principles for expanding the chemical diversity and scope of these platforms for quantum science. We present a comprehensive study of the structure and electronic properties in alkaline earth metal acetylides with high-resolution microwave spectra of 17 isotopologues of MgCCH, CaCCH, and SrCCH in their ground electronic states. The precise semiexperimental equilibrium geometry of each species has been derived by correcting the measured rotational constants for electronic and zero-point vibrational contributions calculated with high-level quantum chemistry methods. The well-resolved hyperfine structure associated with the H, C, and metal nuclear spins provides further information on the distribution and hybridization of the metal-centered, optically active unpaired electron. Together, these measurements allow us to correlate trends in chemical bonding and structure with the electronic properties that promote efficient optical cycling essential to next-generation experiments in precision measurement and quantum control of complex polyatomic molecules.
碱土金属-配体分子独特的光学循环效率使得多原子激光冷却和俘获技术取得了重大进展。旋转光谱是探测支撑光学循环的分子特性的理想工具，从而阐明了扩展这些平台在量子科学中的化学多样性和应用范围的设计原则。我们通过对处于基态的 17 种 MgCCH、CaCCH 和 SrCCH 的同位素的高分辨率微波光谱，对碱土金属乙炔的结构和电子性质进行了全面研究。通过用高精度量子化学方法计算的电子和零点振动贡献来校正测量的转动常数，从而推导出每个物种的精确半实验平衡几何形状。与 H、C 和金属核自旋相关的精细结构提供了有关金属中心、光学活性未配对电子的分布和杂化的进一步信息。这些测量结果使我们能够将化学键合和结构的趋势与促进下一代精密测量和复杂多原子分子量子控制实验中所需的有效光学循环的电子性质联系起来。
