《科学》(20211119出版)一周论文导读

编译 | 未玖 Science, 19 NOVEMBER 2021, VOL 374, ISSUE 6570 …

编译 | 未玖

Science, 19 NOVEMBER 2021, VOL 374, ISSUE 6570

《科学》2021年11月19日,第374卷,6570期

天文学Astronomy

The depth of Jupiter’s Great Red Spot constrained by Juno gravity overflights

朱诺号重力测量限制了木星大红斑的深度

▲ 作者:MARZIA PARISI, YOHAI KASPI, ELI GALANTI, DANIELE DURANTE, SCOTT J. BOLTON, STEVEN M. LEVIN, ET AL.

▲ 链接:

https://www.science.org/doi/10.1126/science.abf1396

▲ 摘要

木星的大红斑(GRS)是太阳系中最大的大气涡旋,已被观测了至少两个世纪。目前尚不清楚该涡旋在可见云顶下延伸的深度。

研究组使用朱诺号航天器与木星12次相遇的数据,包括两次直接飞越GRS的数据,评估了GRS的重力特征。因GRS的存在造成的局部密度异常导致探测器视向速度发生偏移。

使用两种不同的方法来推断GRS深度产生了一致的结果,研究组得出结论,GRS在木星大气层顶部以下500公里的范围内。

▲ Abstract

Jupiter’s Great Red Spot (GRS) is the largest atmospheric vortex in the Solar System and has been observed for at least two centuries. It has been unclear how deep the vortex extends beneath its visible cloud tops. We examined the gravity signature of the GRS using data from 12 encounters of the Juno spacecraft with the planet, including two direct overflights of the vortex. Localized density anomalies due to the presence of the GRS caused a shift in the spacecraft line-of-sight velocity. Using two different approaches to infer the GRS depth, which yielded consistent results, we conclude that the GRS is contained within the upper 500 kilometers of Jupiter’s atmosphere.

Microwave observations reveal the deep extent and structure of Jupiter’s atmospheric vortices

微波观测揭示木星大气涡旋的深度和结构

▲ 作者:S. J. BOLTON, S. M. LEVIN, T. GUILLOT, C. LI, Y. KASPI, G. ORTON, ET AL.

▲ 链接:

https://www.science.org/doi/10.1126/science.abf1015

▲ 摘要

木星的大气层充斥着由大小不一涡旋组成的区域和风带,其中最大的是大红斑。这些特征如何随深度变化尚不清楚,其结构的理论范围从浅层气象特征一直到深层对流的表层表现。

研究组使用朱诺号航天器的微波辐射计观测大气涡旋。他们发现漩涡的根部延伸到比水预期凝结深度更深的地方,并且确定了密度逆温层。该研究结果限制了木星涡漩的三维结构及其在云层下的延伸。

▲ Abstract

Jupiter’s atmosphere has a system of zones and belts punctuated by small and large vortices, the largest being the Great Red Spot. How these features change with depth is unknown, with theories of their structure ranging from shallow meteorological features to surface expressions of deep-seated convection. We present observations of atmospheric vortices using the Juno spacecraft’s Microwave Radiometer. We found vortex roots that extend deeper than the altitude at which water is expected to condense, and we identified density inversion layers. Our results constrain the three-dimensional structure of Jupiter’s vortices and their extension below the clouds.

物理学Physics

Quantum mechanical double slit for molecular scattering

分子散射量子力学双缝

▲ 作者:HAOWEN ZHOU, WILLIAM E. PERREAULT, NANDINI MUKHERJEE AND RICHARD N. ZARE

▲ 链接:

https://www.science.org/doi/10.1126/science.abl4143

▲ 摘要

在双缝实验中观察到的干涉最能证明粒子的波动特性。研究组利用斯塔克诱导绝热拉曼通道,通过旋转振动激发双轴(v=2,j=2)态下的分子氘(D2),构建了一个量子力学双缝干涉仪,其中v和j分别表示振动和旋转量子数。

在D2(v=2,j=2)→ D2(v=2,j′=0)通过与基态氦冷碰撞的旋转弛豫中,双轴态中的两个相干耦合键轴方向充当两个狭缝,产生两种不可区分的量子力学路径,连接碰撞系统的初始和最终状态。

当研究组通过分别构造D2的单轴态来解耦键轴的两个方向时,干涉消失了,因此明确建立了双轴态的双缝作用。这种双缝设计为分子碰撞的相干控制开辟了新途径。

▲ Abstract

Interference observed in a double-slit experiment most conclusively demonstrates the wave properties of particles. We construct a quantum mechanical double-slit interferometer by rovibrationally exciting molecular deuterium (D2) in a biaxial (v = 2, j = 2) state using Stark-induced adiabatic Raman passage, where v and j represent the vibrational and rotational quantum numbers, respectively. In D2 (v = 2, j = 2) → D2 (v = 2, j′ = 0) rotational relaxation via a cold collision with ground state helium, the two coherently coupled bond axis orientations in the biaxial state act as two slits that generate two indistinguishable quantum mechanical pathways connecting initial and final states of the colliding system. The interference disappears when we decouple the two orientations of the bond axis by separately constructing the uniaxial states of D2, unequivocally establishing the double-slit action of the biaxial state. This double slit opens new possibilities in the coherent control of molecular collisions.

Observation of Pauli blocking in light scattering from quantum degenerate fermions

量子简并费米子光散射中泡利阻塞的观测

▲ 作者:AMITA B. DEB AND NIELS KJÆRGAARD

▲ 链接:

https://www.science.org/doi/10.1126/science.abh3470

▲ 摘要

泡利不相容原理禁止无法区分的费米子占据相同的量子力学状态。其影响是深远的;例如,它解释了原子的电子壳层结构。

研究组对超冷原子群的光散射进行了测量。对于量子简并区的费米气体,他们观察到与类似制备的玻色气体相比,散射有明显的抑制。

观察到的荧光减少和相应的透光率增加是泡利阻塞的结果,其中费米-狄拉克统计限制了大费米海中散射原子的可访问态数目。该工作证实了量子气体光学响应的基本结果,或可有助于冷却和测温方案。

▲ Abstract

The Pauli exclusion principle forbids indistinguishable fermions from occupying the same quantum mechanical state. The implications of this are profound; for example, it accounts for the electronic shell structure of atoms. Here, we performed measurements on the scattering of light from ultracold ensembles of atoms. For a Fermi gas in the quantum degenerate regime, we observed a marked suppression in scattering compared with a similarly prepared Bose gas. The observed decrease in fluorescence and the corresponding increase in light transmission results from Pauli blocking, where Fermi-Dirac statistics limits the number of accessible states for a scattering atom in a large Fermi sea. Our work confirms a fundamental result on the optical response of quantum gases and may contribute to cooling and thermometry schemes.

Pauli blocking of atom-light scattering

原子光散射的泡利阻塞

▲ 作者:CHRISTIAN SANNER, LINDSAY SONDERHOUSE, ROSS B. HUTSON, LINGFENG YAN, WILLIAM R. MILNER AND JUN YE

▲ 链接:

https://www.science.org/doi/10.1126/science.abh3483

▲ 摘要

量子系统中耦合态之间的跃迁率取决于可用最终态的密度。通过降低原子跃迁附近的电磁真空模式的密度,可以抑制激发原子态的辐射衰减。同样,当原子运动嵌入费米海时,降低其可用动量模式的密度将抑制自发辐射和光子散射率。

研究组报道了在量子简并费米气体中抑制光散射的实验证明。他们系统地测量了抑制因子对锶量子气体的温度和费米能量的依赖性,并实现了与热气体相比高达2倍的散射率抑制。

▲ Abstract

Transition rates between coupled states in a quantum system depend on the density of available final states. The radiative decay of an excited atomic state has been suppressed by reducing the density of electromagnetic vacuum modes near the atomic transition. Likewise, reducing the density of available momentum modes of the atomic motion when it is embedded inside a Fermi sea will suppress spontaneous emission and photon scattering rates. Here we report the experimental demonstration of suppressed light scattering in a quantum degenerate Fermi gas. We systematically measured the dependence of the suppression factor on the temperature and Fermi energy of a strontium quantum gas and achieved suppression of scattering rates by up to a factor of 2 compared with a thermal gas.

材料科学Materials Science

Gradient cell–structured high-entropy alloy with exceptional strength and ductility

具有超高强度和塑性的梯度胞结构高熵合金

▲ 作者:QINGSONG PAN, LIANGXUE ZHANG, RUI FENG, QIUHONG LU, KE AN, ANDREW CHIHPIN CHUANG, ET AL.

▲ 链接:

https://www.science.org/doi/10.1126/science.abj8114

▲ 摘要

与传统材料类似,大多数多组分高熵合金(HEAs)在获得强度的同时会失去塑性。在该项研究中,研究组在具有面心立方结构的稳定单相HEA中可控地引入梯度纳米级位错胞结构,从而在没有明显塑性损失的情况下提高强度。

当施加应变时,样品-水平结构梯度诱导高密度的微小堆垛层错(SF)和孪晶逐渐形成,从大量的低角度位错胞中形核。此外,SF诱导的塑性和由此产生的细化结构,加上高密度聚集的位错,有助于塑性、强度增加和加工硬化。

这些发现为在纳米尺度上使用梯度位错胞的调控特性提供了一个有前景的范例,并推进了人们对HEA内在变形行为的基本理解。

▲ Abstract

Similar to conventional materials, most multicomponent high-entropy alloys (HEAs) lose ductility as they gain strength. In this study, we controllably introduced gradient nanoscaled dislocation cell structures in a stable single-phase HEA with face-centered cubic structure, thus resulting in enhanced strength without apparent loss of ductility. Upon application of strain, the sample-level structural gradient induces progressive formation of a high density of tiny stacking faults (SFs) and twins, nucleating from abundant low-angle dislocation cells. Furthermore, the SF-induced plasticity and the resultant refined structures, coupled with intensively accumulated dislocations, contribute to plasticity, increased strength, and work hardening. These findings offer a promising paradigm for tailoring properties with gradient dislocation cells at the nanoscale and advance our fundamental understanding of the intrinsic deformation behavior of HEAs.

为您推荐

发表评论

您的电子邮箱地址不会被公开。 必填项已用*标注

此站点使用Akismet来减少垃圾评论。了解我们如何处理您的评论数据