弱束缚负离子的新电子能谱

弱耦合囚禁离子机械振子的间接冷却

Indirect Cooling of Weakly Coupled Trapped-Ion Mechanical Oscillators

本文提出利用囚禁势参量调制将弱冷却辐射耦合模式与强冷却辐射耦合模式耦合，实现囚禁离子晶体中难以直接冷却运动模式的间接近基态冷却，并在多种同种及混合离子晶体中验证了该方法的有效性。

Magnetized Plasma Sheath in the Presence of Negative Ions

The sheath formation in a weakly magnetized collisionless electronegative plasma consisting of electrons, negative and positive ions has been numerically investigated using the hydrodynamic equations. The electrons and negative ions are assumed to follow Boltzmann relation. A sheath formation criterion has been analytically derived. The paper focuses on studying the sheath structure by varying the electronegativity. It has been observed that the presence of negative ions has a substantial effect on the sheath structure. The observations made in the present work have profound significance on pr…

电子在SF6上的附着和SF6 -负离子的寿命

Electron attachment to SF6 and lifetimes of SF6- negative ions

研究了SF6分子对低能电子的俘获过程。我们的方法是基于Gauyacq和Herzenberg [J. Phys. B 17，1155（1984）]的模型，其中电子运动通过弱束缚或虚s态耦合到完全对称的振动模式。通过调整模型的两个自由参数，我们实现了对测量的电子附着截面的精确描述，并与完全对称模的振动激发截面有很好的一致性。该模型的扩展提供了一个限制的特征时间的分子内振动弛豫在高激发SF6-。通过计算SF6-的总振动谱密度，我们估算了长寿命负离子的振动费什巴赫共振宽度。我们还分析了可能的宽度分布及其对寿命测量的影响，并研究了亚稳态SF6-的非指数衰减特性。

Algorithmic Ground-state Cooling of Weakly-Coupled Oscillators using Quantum Logic

Most ions lack the fast, cycling transitions that are necessary for direct laser cooling. In most cases, they can still be cooled sympathetically through their Coulomb interaction with a second, coolable ion species confined in the same potential. If the charge-to-mass ratios of the two ion types are too mismatched, the cooling of certain motional degrees of freedom becomes difficult. This limits both the achievable fidelity of quantum gates and the spectroscopic accuracy. Here we introduce a novel algorithmic cooling protocol for transferring phonons from poorly- to efficiently-cooled modes. …

Controlling the nature of a charged impurity in a bath of Feshbach dimers

We theoretically study the dynamics of a trapped ion that is immersed in an ultracold gas of weakly bound atomic dimers created by a Feshbach resonance. Using quasi-classical simulations, we find a crossover from dimer dissociation to molecular ion formation depending on the binding energy of the dimers. The location of the crossover strongly depends on the collision energy and the time-dependent fields of the Paul trap. Deeply bound dimers lead to fast molecular ion formation, with rates approaching the Langevin collision rate $Γ'_\text{L}\approx4.8\times10^{-9}\,$cm$^3$s$^{-1}$. The kinetic …

Vibrational quenching of cold molecular ions immersed in their parent gas

Hybrid ion-atom systems provide an excellent platform for studies of state-resolved quantum chemistry at low temperatures, where quantum effects may be prevalent. Here we study theoretically the process of vibrational relaxation of an initially weakly bound molecular ion due to collisions with the background gas atoms. We show that this inelastic process is governed by the universal long-range part of the interaction potential, which allows for using simplified model potentials applicable to multiple atomic species. The product distribution after the collision can be estimated by making use of…

超低能离子中性化学：离子-原子混合阱中laser冷却的Ca^+离子与Rb原子反应碰撞的动力学

Ion-neutral chemistry at ultralow energies: Dynamics of reactive collisions between laser-cooled Ca^+ ions and Rb atoms in an ion-atom hybrid trap

在离子-原子混合阱中研究了激光冷却Ca^+离子与Rb原子的冷化学反应。在碰撞能< E_{coll} >/kB = 20 mK-20 K范围内测定了反应的反应速率常数。在使用单个局域化Ca^+离子的实验中，能量最低。使用共振激发质谱法研究产物分支比。利用CaRb^+势能曲线的高级量子化学计算和辐射通道的量子散射计算，分析了该体系中反应过程的动力学（非辐射和辐射电荷转移以及导致CaRb^+分子离子形成的辐射缔合）。对于目前的低能散射实验，它表明，反应速率常数的能量依赖性是由长程相互作用与经典的朗之万模型，但它们的大小是由短程非绝热和辐射耦合，只有弱依赖于渐近能量。碰撞的量子特性的预测表现在发生狭窄的形状共振在定义明确的碰撞能量。目前的结果突出了冷离子中性反应碰撞中的普遍和系统特定的现象。

三体系统旋转激发束缚态的高精度计算

Highly accurate calculations of the rotationally excited bound states in three-body systems

提出了一种有效的优化策略，用于构造各种三体系统的高精度束缚态波函数。我们的程序似乎是非常有效的计算弱束缚态和各种激发态，包括旋转激发态，即与$L \ge 1$的状态。对$ddμ, dtμ$和$ttμ$ μ子分子离子的$P^{*}(L = 1)-$激发态、非对称$pdμ, ptμ$和$dtμ$离子的$P(L = 1)-$态以及He原子的$2^{1}P(L = 1)-$和$2^{3}P(L = 1)-$态的计算表明了我们方法的有效性.

Black-body radiation induced photodissociation and population redistribution of weakly bound states in H$_2^+$

Molecular hydrogen ions in weakly bound states close to the first dissociation threshold are attractive quantum sensors for measuring the proton-to-electron mass ratio and hyperfine-induced ortho-para mixing. The experimental accuracy of previous spectroscopic studies relying on fast ion beams could be improved by using state-of-the-art ion trap setups. With the electric dipole moment vanishing in H$_2^+$ and preventing fast spontaneous emission, radiative lifetimes of the order of weeks are found. We include the effect of black-body radiation that can lead to photodissociation and rovibronic …

Classical molecular dynamic simulations and modelling of inverse-bremsstrahlung heating in low Z weakly-coupled plasmas

Classical molecular-dynamics simulations (CMDS) have been conducted to investigate one of the main mechanism responsible for absorption of radiation by matter namely stimulated inverse bremsstrahlung. CMDS of two components plasmas (electrons and ions) for a large range of electron densities, electron temperatures, for ionization $Z=1$, were carried out with 2 million particles using the code LAMMPS. A parameterized model (with 6 adjustable constants), which encompasses most theoretical models proposed in the past to quantify heating rate by stimulated inverse bremsstrahlung, serves as a refer…

光激发大尺寸He纳米液滴中光谱分辨的共振原子间库仑衰变

Spectroscopically resolved resonant interatomic Coulombic decay in photoexcited large He nanodroplets

本研究利用大尺寸氦纳米液滴，发现弱同步辐射下低、高于电离阈值均能发生ICD，揭示次级过程的关键作用，并证明ICD可用于监测弱键合纳米系统弛豫动力学。