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Characterization and source analysis of water-soluble ions in PM2.5 at a background site in Central China 期刊论文
ATMOSPHERIC RESEARCH, 2020, 239
作者:  Xie, Yajun;  Lu, Haibo;  Yi, Aijun;  Zhang, Zhongyi;  Zheng, Nengjian;  Fang, Xiaozhen;  Xiao, Huayun
收藏  |  浏览/下载:31/0  |  提交时间:2020/08/18
PM2.5  SNA  Water-soluble ions characteristics  Formation mechanism  Source identification  Central China  
Upstream Ultra-Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Romanelli, N.;  DiBraccio, G.;  Gershman, D.;  Le, G.;  Mazelle, C.;  Meziane, K.;  Boardsen, S.;  Slavin, J.;  Raines, J.;  Glass, A.;  Espley, J.
收藏  |  浏览/下载:40/0  |  提交时间:2020/05/13
Mercury  foreshock  ULF waves  backstreaming ions  bow shock  magnetic field  
Quantum entanglement between an atom and a molecule 期刊论文
NATURE, 2020, 581 (7808) : 273-+
作者:  Trisos, Christopher H.;  Merow, Cory;  Pigot, Alex L.
收藏  |  浏览/下载:44/0  |  提交时间:2020/07/03

Conventional information processors convert information between different physical carriers for processing, storage and transmission. It seems plausible that quantum information will also be held by different physical carriers in applications such as tests of fundamental physics, quantum enhanced sensors and quantum information processing. Quantum controlled molecules, in particular, could transduce quantum information across a wide range of quantum bit (qubit) frequencies-from a few kilohertz for transitions within the same rotational manifold(1), a few gigahertz for hyperfine transitions, a few terahertz for rotational transitions, to hundreds of terahertz for fundamental and overtone vibrational and electronic transitions-possibly all within the same molecule. Here we demonstrate entanglement between the rotational states of a (CaH+)-Ca-40 molecular ion and the internal states of a Ca-40(+) atomic ion(2). We extend methods used in quantum logic spectroscopy(1,3) for pure-state initialization, laser manipulation and state readout of the molecular ion. The quantum coherence of the Coulomb coupled motion between the atomic and molecular ions enables subsequent entangling manipulations. The qubit addressed in the molecule has a frequency of either 13.4 kilohertz(1) or 855 gigahertz(3), highlighting the versatility of molecular qubits. Our work demonstrates how molecules can transduce quantum information between qubits with different frequencies to enable hybrid quantum systems. We anticipate that our method of quantum control and measurement of molecules will find applications in quantum information science, quantum sensors, fundamental and applied physics, and controlled quantum chemistry.


Quantum entanglement is realized between rotational levels of a molecular ion with energy differences spanning several orders of magnitude and long-lived internal states of a single atomic ion.


  
Chemical characterization and source analysis of water-soluble inorganic ions in PM2.5 from a plateau city of Kunming at different seasons 期刊论文
ATMOSPHERIC RESEARCH, 2020, 234
作者:  Guo, Wei;  Zhang, Zhongyi;  Zheng, Nengjian;  Luo, Li;  Xiao, Huayun;  Xiao, Hongwei
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/02
PM2.5  Water-soluble inorganic ions (WSIIs)  Source identification  Seasonality  Kunming  
Measurement of mercury, other trace elements and major ions in wet deposition at Jomsom: The semi-arid mountain valley of the Central Himalaya 期刊论文
ATMOSPHERIC RESEARCH, 2020, 234
作者:  Tripathee, Lekhendra;  Guo, Junming;  Kang, Shichang;  Paudyal, Rukumesh;  Sharma, Chhatra Mani;  Huang, Jie;  Chen, Pengfei;  Ghimire, Prakriti Sharma;  Sigdel, Madan;  Sillanpaa, Mika
收藏  |  浏览/下载:23/0  |  提交时间:2020/07/02
Mercury  Trace elements  Major ions  Wet deposition  Semi-arid region  Himalayas  
Detection of metastable electronic states by Penning trap mass spectrometry 期刊论文
NATURE, 2020, 581 (7806) : 42-+
作者:  Rauch, Jennifer N.;  Luna, Gabriel;  Guzman, Elmer;  Audouard, Morgane;  Challis, Collin;  Sibih, Youssef E.;  Leshuk, Carolina;  Hernandez, Israel;  Wegmann, Susanne;  Hyman, Bradley T.;  Gradinaru, Viviana;  Kampmann, Martin;  Kosik, Kenneth S.
收藏  |  浏览/下载:27/0  |  提交时间:2020/07/03

State-of-the-art optical clocks(1) achieve precisions of 10(-18) or better using ensembles of atoms in optical lattices(2,3) or individual ions in radio-frequency traps(4,5). Promising candidates for use in atomic clocks are highly charged ions(6) (HCIs) and nuclear transitions(7), which are largely insensitive to external perturbations and reach wavelengths beyond the optical range(8) that are accessible to frequency combs(9). However, insufficiently accurate atomic structure calculations hinder the identification of suitable transitions in HCIs. Here we report the observation of a long-lived metastable electronic state in an HCI by measuring the mass difference between the ground and excited states in rhenium, providing a non-destructive, direct determination of an electronic excitation energy. The result is in agreement with advanced calculations. We use the high-precision Penning trap mass spectrometer PENTATRAP to measure the cyclotron frequency ratio of the ground state to the metastable state of the ion with a precision of 10(-11)-an improvement by a factor of ten compared with previous measurements(10,11). With a lifetime of about 130 days, the potential soft-X-ray frequency reference at 4.96 x 10(16) hertz (corresponding to a transition energy of 202 electronvolts) has a linewidth of only 5 x 10(-8) hertz and one of the highest electronic quality factors (10(24)) measured experimentally so far. The low uncertainty of our method will enable searches for further soft-X-ray clock transitions(8,12) in HCIs, which are required for precision studies of fundamental physics(6).


Penning trap mass spectrometry is used to measure the electronic transition energy from a long-lived metastable state to the ground state in highly charged rhenium ions with a precision of 10(-11).


  
A general carbonyl alkylative amination for tertiary amine synthesis 期刊论文
NATURE, 2020
作者:  Ouyang, David;  He, Bryan;  Ghorbani, Amirata;  Yuan, Neal;  Ebinger, Joseph;  Langlotz, Curtis P.;  Heidenreich, Paul A.;  Harrington, Robert A.;  Liang, David H.;  Ashley, Euan A.;  Zou, James Y.
收藏  |  浏览/下载:26/0  |  提交时间:2020/07/03

The ubiquity of tertiary alkylamines in pharmaceutical and agrochemical agents, natural products and small-molecule biological probes(1,2) has stimulated efforts towards their streamlined synthesis(3-9). Arguably the most robust method for the synthesis of tertiary alkylamines is carbonyl reductive amination(3), which comprises two elementary steps: the condensation of a secondary alkylamine with an aliphatic aldehyde to form an all-alkyl-iminium ion, which is subsequently reduced by a hydride reagent. Direct strategies have been sought for a '  higher order'  variant of this reaction via the coupling of an alkyl fragment with an alkyl-iminium ion that is generated in situ(10-14). However, despite extensive efforts, the successful realization of a '  carbonyl alkylative amination'  has not yet been achieved. Here we present a practical and general synthesis of tertiary alkylamines through the addition of alkyl radicals to all-alkyl-iminium ions. The process is facilitated by visible light and a silane reducing agent, which trigger a distinct radical initiation step to establish a chain process. This operationally straightforward, metal-free and modular transformation forms tertiary amines, without structural constraint, via the coupling of aldehydes and secondary amines with alkyl halides. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of complex tertiary amines.


The synthesis of tertiary amines is achieved through a carbonyl alkylative amination reaction facilitated by visible light, in which an aldehyde and an amine condense to form an iminium ion that subsequently reacts with alkyl radical.


  
Ionic solids from common colloids 期刊论文
NATURE, 2020, 580 (7804) : 487-+
作者:  Delord, T.;  Huillery, P.;  Nicolas, L.;  Hetet, G.
收藏  |  浏览/下载:25/0  |  提交时间:2020/07/03

Oppositely charged colloidal particles are assembled in water through an approach that allows electrostatic interactions to be precisely tuned to generate macroscopic single crystals.


From rock salt to nanoparticle superlattices, complex structure can emerge from simple building blocks that attract each other through Coulombic forces(1-4). On the micrometre scale, however, colloids in water defy the intuitively simple idea of forming crystals from oppositely charged partners, instead forming non-equilibrium structures such as clusters and gels(5-7). Although various systems have been engineered to grow binary crystals(8-11), native surface charge in aqueous conditions has not been used to assemble crystalline materials. Here we form ionic colloidal crystals in water through an approach that we refer to as polymer-attenuated Coulombic self-assembly. The key to crystallization is the use of a neutral polymer to keep particles separated by well defined distances, allowing us to tune the attractive overlap of electrical double layers, directing particles to disperse, crystallize or become permanently fixed on demand. The nucleation and growth of macroscopic single crystals is demonstrated by using the Debye screening length to fine-tune assembly. Using a variety of colloidal particles and commercial polymers, ionic colloidal crystals isostructural to caesium chloride, sodium chloride, aluminium diboride and K4C60 are selected according to particle size ratios. Once fixed by simply diluting out solution salts, crystals are pulled out of the water for further manipulation, demonstrating an accurate translation from solution-phase assembly to dried solid structures. In contrast to other assembly approaches, in which particles must be carefully engineered to encode binding information(12-18), polymer-attenuated Coulombic self-assembly enables conventional colloids to be used as model colloidal ions, primed for crystallization.


  
Mass spectrometry for future atomic clocks 期刊论文
NATURE, 2020, 581 (7806) : 35-36
作者:  Padian, Kevin
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/03

Measurement of a metastable electronic state in a highly charged ion.


Highly charged ions could form the basis of the next generation of ultra-precise clocks, using electronic transitions in the ions as the '  pendulum'  . An ingenious method for characterizing such transitions has been reported.


  
Control and single-shot readout of an ion embedded in a nanophotonic cavity 期刊论文
NATURE, 2020, 580 (7802) : 201-+
作者:  Rollie, Clare;  Chevallereau, Anne;  Watson, Bridget N. J.;  Chyou, Te-yuan;  Fradet, Olivier;  McLeod, Isobel;  Fineran, Peter C.;  Brown, Chris M.;  Gandon, Sylvain;  Westra, Edze R.
收藏  |  浏览/下载:45/0  |  提交时间:2020/07/03

Distributing entanglement over long distances using optical networks is an intriguing macroscopic quantum phenomenon with applications in quantum systems for advanced computing and secure communication(1,2). Building quantum networks requires scalable quantum light-matter interfaces(1) based on atoms(3), ions(4) or other optically addressable qubits. Solid-state emitters(5), such as quantum dots and defects in diamond or silicon carbide(6-10), have emerged as promising candidates for such interfaces. So far, it has not been possible to scale up these systems, motivating the development of alternative platforms. A central challenge is identifying emitters that exhibit coherent optical and spin transitions while coupled to photonic cavities that enhance the light-matter interaction and channel emission into optical fibres. Rare-earth ions in crystals are known to have highly coherent 4f-4f optical and spin transitions suited to quantum storage and transduction(11-15), but only recently have single rare-earth ions been isolated(16,17) and coupled to nanocavities(18,19). The crucial next steps towards using single rare-earth ions for quantum networks are realizing long spin coherence and single-shot readout in photonic resonators. Here we demonstrate spin initialization, coherent optical and spin manipulation, and high-fidelity single-shot optical readout of the hyperfine spin state of single Yb-171(3+) ions coupled to a nanophotonic cavity fabricated in an yttrium orthovanadate host crystal. These ions have optical and spin transitions that are first-order insensitive to magnetic field fluctuations, enabling optical linewidths of less than one megahertz and spin coherence times exceeding thirty milliseconds for cavity-coupled ions, even at temperatures greater than one kelvin. The cavity-enhanced optical emission rate facilitates efficient spin initialization and single-shot readout with conditional fidelity greater than 95 per cent. These results showcase a solid-state platform based on single coherent rare-earth ions for the future quantum internet.


Single ytterbium ion qubits in nanophotonic cavities have long coherence times and can be optically read out in a single shot, establishing them as excellent candidates for optical quantum networks.