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In-orbit operation of an atomic clock based on laser-cooled ⁸⁷Rb atoms.

ABSTRACT: Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth's radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10^-13τ^-1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

SUBMITTER: Liu L

PROVIDER: S-EPMC6057979 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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In-orbit operation of an atomic clock based on laser-cooled <sup>87</sup>Rb atoms.

Liu Liang L Lü De-Sheng DS Chen Wei-Biao WB Li Tang T Qu Qiu-Zhi QZ Wang Bin B Li Lin L Ren Wei W Dong Zuo-Ren ZR Zhao Jian-Bo JB Xia Wen-Bing WB Zhao Xin X Ji Jing-Wei JW Ye Mei-Feng MF Sun Yan-Guang YG Yao Yuan-Yuan YY Song Dan D Liang Zhao-Gang ZG Hu Shan-Jiang SJ Yu Dun-He DH Hou Xia X Shi Wei W Zang Hua-Guo HG Xiang Jing-Feng JF Peng Xiang-Kai XK Wang Yu-Zhu YZ

Nature communications 20180724 1

Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of ...[more]

PMID: 30042419

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Project description:In addition to amide hydrogen bonds and the hydrophobic effect, interactions involving π-bonded sp 2 atoms of amides, aromatics and other groups occur in protein self-assembly processes including folding, oligomerization and condensate formation. These interactions also occur in aqueous solutions of amide and aromatic compounds, where they can be quantified. Previous analysis of thermodynamic coefficients quantifying net-favorable interactions of amide compounds with other amides and aromatics revealed that interactions of amide sp 2 O with amide sp 2 N unified atoms (presumably C=O···H-N hydrogen bonds) and amide/aromatic sp 2 C (lone pair-π, n-π * ) are particularly favorable. Sp 3 C-sp 3 C (hydrophobic), sp 3 C-sp 2 C (hydrophobic, CH-π), sp 2 C-sp 2 C (hydrophobic, π-π) and sp 3 C-sp 2 N interactions are favorable, sp 2 C-sp 2 N interactions are neutral, while sp 2 O-sp 2 O and sp 2 N-sp 2 N self-interactions and sp 2 O-sp 3 C interactions are unfavorable. Here, from determinations of favorable effects of fourteen amides on naphthalene solubility at 10, 25 and 45 °C, we dissect amide-aromatic interaction free energies into enthalpic and entropic contributions and find these vary systematically with amide composition. Analysis of these results yields enthalpic and entropic contributions to intrinsic strengths of interactions of amide sp 2 O, sp 2 N, sp 2 C and sp 3 C unified atoms with aromatic sp 2 C atoms. For each interaction, enthalpic and entropic contributions have the same sign and are much larger in magnitude than the interaction free energy itself. The amide sp 2 O-aromatic sp 2 C interaction is enthalpy-driven and entropically unfavorable, consistent with direct chemical interaction (e.g. lone pair-π) while amide sp 3 C- and sp 2 C-aromatic sp 2 C interactions are entropy-driven and enthalpically unfavorable, consistent with hydrophobic effects. These findings are relevant for interactions involving π-bonded sp 2 atoms in protein processes.Table of contents graphic

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In-orbit operation of an atomic clock based on laser-cooled ⁸⁷Rb atoms.

Publications

In-orbit operation of an atomic clock based on laser-cooled <sup>87</sup>Rb atoms.

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In-orbit operation of an atomic clock based on laser-cooled 87Rb atoms.

Publications

In-orbit operation of an atomic clock based on laser-cooled <sup>87</sup>Rb atoms.

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OmicsDI is part of the ELIXIR infrastructure

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In-orbit operation of an atomic clock based on laser-cooled ⁸⁷Rb atoms.