Life and death of a cold BaRb$^+$ molecule inside an ultracold cloud of Rb atoms

Vibrational quenching and reactive processes of weakly bound molecular ion-atom collisions at cold temperatures

We present a study of vibrational quenching and chemical processes of molecular ions immersed in an ultracold atomic gas by means of the quasi-classical trajectory (QCT) method. In particular, BaRb$^+(v)$ + Rb collisions are studied at cold temperatures revealing a highly efficient energy transfer between the translational degrees of freedom and internal degrees of the molecular ion. Thus leading to a large vibrational quenching cross section which follows the Langevin capture model prediction. These results play a key role on the understanding of relaxation phenomena of cold molecular ions in…

Birth, life, and death of a dipolar supersolid

In the short time since the first observation of supersolid states of ultracold dipolar atoms, substantial progress has been made in understanding the zero-temperature phase diagram and low-energy excitations of these systems. Less is known, however, about their finite-temperature properties, particularly relevant for supersolids formed by cooling through direct evaporation. Here, we explore this realm by characterizing the evaporative formation and subsequent decay of a dipolar supersolid by combining high-resolution in-trap imaging with time-of-flight observables. As our atomic system cools …

The RbSr $^2Σ^+$ ground state investigated via spectroscopy of hot & ultracold molecules

We report on spectroscopic studies of hot and ultracold RbSr molecules, and combine the results in an analysis that allows us to fit a potential energy curve (PEC) for the X(1)$^2Σ^+$ ground state bridging the short-to-long-range domains. The ultracold RbSr molecules are created in a $μ$K sample of Rb and Sr atoms and probed by two-colour photoassociation spectroscopy. The data yield the long-range dispersion coefficients $C_6$ and $C_8$, along with the total number of supported bound levels. The hot RbSr molecules are created in a $1000 \,$K gas mixture of Rb and Sr in a heat-pipe oven and pr…

Ba $^+$离子与超冷Rb原子碰撞的交感冷却：理论展望

Sympathetic cooling of the Ba$^+$ ion by collisions with ultracold Rb atoms: theoretical prospects

本文应用最新的{ \em ab initio}方法在Born-Oppenheimer近似下计算了（BaRb）$^+$分子离子的势能曲线。描述在大原子间距离的静电，感应和色散相互作用的长程系数也报道。控制X $^1Σ\to ^1Σ, ^1Π$的电跃迁偶极矩作为极化传播子的第一留数，用线性响应耦合簇方法计算，仅限于单激发和双激发。非绝热的径向和角耦合矩阵元素，以及自旋轨道耦合矩阵元素已被评估使用多参考配置相互作用方法限制到一个大的活动空间的单和双激发。利用这些耦合，得到了与实验相关的0 $^+$和1态的自旋-轨道耦合（相对论）势能曲线。最后，由非相对论结果和自旋轨道本征矢得到了相对论跃迁矩和非绝热耦合矩阵元。采用电子结构输入计算了Ba $^+$离子与Rb原子的碰撞截面。在这些计算中使用了非相对论和相对论势。我们的结果表明，非弹性截面对应的从Rb原子的Ba $^+$离子的电荷转移是远远小于弹性的一个在很宽的范围内的能量高达1 mK。这表明Ba $^+$离子通过与超冷Rb原子碰撞而产生的共振冷却是可能的。