四极阴离子的共振光谱
Resonant spectra of quadrupolar anions
摘要：
在四极束缚的阴离子中，一个额外的电子附着在中性分子的足够大的四极矩上，而中性分子缺乏永久的偶极矩。这些阴离子的束缚态和低共振态的性质对于理解一般开放量子系统的阈值行为是有意义的。在这项工作中，我们调查的性质四极阴离子极端晕系统，形成的旋转带，从亚临界到超临界电四极矩的过渡。我们解决了电子加分子的问题，使用非绝热耦合通道的形式主义，采用Berggren系综，其中明确包含束缚态，窄共振，和散射连续。我们证明了四极负离子的结合能和半径严格遵循两体晕系统的标度律。与偶极阴离子的情况相反，四极阴离子的基态带平滑地延伸到连续谱中，并且在脱离阈值以上可以识别出许多转动带。我们研究了阴离子束缚态在临界四极矩进入连续介质时的演化，并证明了相应的临界指数与二级相变是一致的。从各方面考虑，四极阴离子是研究边缘束缚开放量子系统的理想实验室。
英文摘要：
In quadrupole-bound anions, an extra electron is attached at a sufficiently large quadrupole moment of a neutral molecule, which is lacking a permanent dipole moment. The nature of the bound states and low-lying resonances of such anions is of interest for understanding the threshold behavior of open quantum systems in general. In this work, we investigate the properties of quadrupolar anions as extreme halo systems, the formation of rotational bands, and the transition from a subcritical to supercritical electric quadrupole moment. We solve the electron-plus-molecule problem using a non-adiabatic coupled-channel formalism by employing the Berggren ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. We demonstrate that binding energies and radii of quadrupolar anions strictly follow the scaling laws for two-body halo systems. Contrary to the case of dipolar anions, ground-state band of quadrupolar anions smoothly extend into the continuum, and many rotational bands could be identified above the detachment threshold. We study the evolution of a bound state of an anion as to dives into the continuum at a critical quadrupole moment and we show that the associated critical exponent is consistent with the second-order phase transition. Everything considered, quadrupolar anions represent a perfect laboratory for the studies of marginally bound open quantum systems.
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