Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
J Am Chem Soc. 2023 Mar 8;145(9):5512-5522. doi: 10.1021/jacs.3c00246. Epub 2023 Feb 21.
The critical dipole moment to bind an electron was empirically determined to be 2.5 debye, even though smaller values were predicted theoretically. Herein, we report the first observation of a polarization-assisted dipole-bound state (DBS) for a molecule with a dipole moment below 2.5 debye. Photoelectron and photodetachment spectroscopies are conducted for cryogenically cooled indolide anions, where the neutral indolyl radical has a dipole moment of 2.4 debye. The photodetachment experiment reveals a DBS only 6 cm below the detachment threshold along with sharp vibrational Feshbach resonances. Rotational profiles are observed for all of the Feshbach resonances, which are found to have surprisingly narrow linewidths and long autodetachment lifetimes attributed to weak coupling between vibrational motions and the nearly free dipole-bound electron. Calculations suggest that the observed DBS has π-symmetry stabilized by the strong anisotropic polarizability of indolyl.
虽然理论上预测的数值更小，但经验确定的能结合一个电子的临界偶极矩为 2.5 德拜。在此，我们报告了首例对低于 2.5 德拜偶极矩的分子的极化辅助偶极束缚态 (DBS)的观测。低温冷却的吲哚阴离子进行光电离和光电子光谱学实验，其中中性吲哚自由基的偶极矩为 2.4 德拜。光电子解离实验仅在离解阈值以下 6 cm 处揭示了 DBS，同时伴有尖锐的振动 Feshbach 共振。所有的 Feshbach 共振都观察到了旋转轮廓，它们具有令人惊讶的窄线宽和长的自离解寿命，这归因于振动运动和几乎自由的偶极束缚电子之间的弱耦合。计算表明，观察到的 DBS 具有由吲哚基强各向异性极化率稳定的π对称性。
