Gao Han-Wen, Choi Hyun Wook, Hui Jie, Chen Wei-Jia, Kocheril G Stephen, Wang Lai-Sheng
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
J Chem Phys. 2023 Sep 21;159(11). doi: 10.1063/5.0170325.
We report a study on the electronic structure and chemical bonding of the BiB molecule using high-resolution photoelectron imaging of cryogenically cooled BiB- anion. By eliminating all the vibrational hot bands, we can resolve the complicated detachment transitions due to the open-shell nature of BiB and the strong spin-orbit coupling. The electron affinity of BiB is measured to be 2.010(1) eV. The ground state of BiB- is determined to be 2Π(3/2) with a σ2π3 valence electron configuration, while the ground state of BiB is found to be 3Σ-(0+) with a σ2π2 electron configuration. Eight low-lying spin-orbit excited states [3Σ-(1), 1Δ(2), 1Σ+(0+), 3Π(2), 3Π(1), 1Π(1)], including two forbidden transitions, [3Π(0-) and 3Π(0+)], are observed for BiB as a result of electron detachment from the σ and π orbitals of BiB-. The angular distribution information from the photoelectron imaging is found to be critical to distinguish detachment transitions from the σ or π orbital for the spectral assignment. This study provides a wealth of information about the low-lying electronic states and spin-orbit coupling of BiB, demonstrating the importance of cryogenic cooling for obtaining well-resolved photoelectron spectra for size-selected clusters produced from a laser vaporization cluster source.
我们报道了一项关于BiB分子电子结构和化学键合的研究，该研究使用了低温冷却的BiB⁻阴离子的高分辨率光电子成像技术。通过消除所有振动热谱带，由于BiB的开壳层性质和强自旋轨道耦合，我们能够解析复杂的离解跃迁。测得BiB的电子亲和能为2.010(1) eV。确定BiB⁻的基态为具有σ²π³价电子构型的²Π(3/2)，而BiB的基态为具有σ²π²电子构型的³Σ⁻(0⁺)。由于电子从BiB⁻的σ和π轨道离解，观察到BiB的八个低自旋轨道激发态[³Σ⁻(1)、¹Δ(2)、¹Σ⁺(0⁺)、³Π(2)、³Π(1)、¹Π(1)]，包括两个禁戒跃迁[³Π(0⁻)和³Π(0⁺)]。发现光电子成像的角分布信息对于区分光谱归属中来自σ或π轨道的离解跃迁至关重要。这项研究提供了关于BiB的低电子态和自旋轨道耦合的丰富信息，证明了低温冷却对于从激光蒸发团簇源产生的尺寸选择团簇获得分辨率良好的光电子能谱的重要性。
