《科學》（20200925出版）一周論文導讀

編譯 | 未玖

Science, 25 SEPTEMBER 2020, VOL 369, ISSUE 6511

《科學》2020年9月25日，第369卷，6511期

物理學Physics

Photon-recoil imaging: Expanding the view of nonlinear x-ray physics

光子反衝成像：非線性X射線物理學的新視野

▲ 作者：U. Eichmann, H. Rottke, S. Meise, J.-E. Rubensson, J. Söderström, M. Agåker, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6511/1630

▲ 摘要

解決電子波函數的超快相干演變一直是非線性X射線物理學的目標。實現這個目標的第一步是研究使用來自X射線自由電子雷射器的強脈衝來激發X射線拉曼散射（SXRS）。

早期SXRS實驗依賴於脈衝在密集諧振介質中傳播時的信號放大。相比之下，研究組的方法揭示了來自主要輻射源的光子直接與單個原子相互作用的基本過程。他們介紹了一種實驗方案，可檢測到散射中性原子而非散射光子。

研究組進行了氖原子K層的SXRS測量和定量理論分析，該方法將成為探索非線性X射線物理研究的有力工具。

▲ Abstract

Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. A first step toward this goal is the investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser. Earlier SXRS experiments relied on signal amplification during pulse propagation through dense resonant media. By contrast, our method reveals the fundamental process in which photons from the primary radiation source directly interact with a single atom. We introduce an experimental protocol in which scattered neutral atoms rather than scattered photons are detected. We present SXRS measurements at the neon K edge and a quantitative theoretical analysis. The method should become a powerful tool in the exploration of nonlinear x-ray physics.

材料學Material Science

Inducing metallicity in graphene nanoribbons via zero-mode superlattices

通過零能模超晶格在石墨烯納米帶中誘導金屬性

▲ 作者：Daniel J. Rizzo, Gregory Veber, Jingwei Jiang, Ryan McCurdy, Ting Cao, Christopher Bronner, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6511/1597

▲ 摘要

在石墨烯納米帶（GNR）中設計和製造穩固的金屬性極具挑戰，因為當在納米尺度上構建石墨烯時，橫向量子限制和多電子相互作用會引起電子帶隙。自下而上合成的最新進展可設計和表徵原子級精密的GNR，但實現GNR金屬性的策略卻一直不清楚。

研究組通過將零能模的對稱超晶格插入半導體GNR中，展示了一種在GNR中誘導金屬性的通用技術。研究組使用掃描隧道光譜以及第一原理密度泛函理論和緊束縛計算來驗證所得的金屬性。

研究結果表明，通過有意破壞子晶格的對稱性來控制零模波函數的重疊，可在很大範圍內調節GNR中的金屬帶寬。

▲ Abstract

The design and fabrication of robust metallic states in graphene nanoribbons (GNRs) are challenging because lateral quantum confinement and many-electron interactions induce electronic band gaps when graphene is patterned at nanometer length scales. Recent developments in bottom-up synthesis have enabled the design and characterization of atomically precise GNRs, but strategies for realizing GNR metallicity have been elusive. Here we demonstrate a general technique for inducing metallicity in GNRs by inserting a symmetric superlattice of zero-energy modes into otherwise semiconducting GNRs. We verify the resulting metallicity using scanning tunneling spectroscopy as well as first-principles density-functional theory and tight-binding calculations. Our results reveal that the metallic bandwidth in GNRs can be tuned over a wide range by controlling the overlap of zero-mode wave functions through intentional sublattice symmetry breaking.

地球科學Earth Science

High-impact marine heatwaves attributable to human-induced global warming

人類引起的全球變暖引發高影響力海洋熱浪

▲ 作者：Charlotte Laufkötter, Jakob Zscheischler, Thomas L. Frölicher.

▲ 連結：

https://science.sciencemag.org/content/369/6511/1621

▲ 摘要

海洋熱浪（MHW）是指在特定區域中海洋溫度極高的時期。在過去的二十年裡，MHW發生在地球的所有海洋盆地中，對海洋生物和生態系統造成了嚴重威脅。然而，對於大多數單獨MHW而言，尚不清楚它們在多大程度上因人類引起的氣候變化而改變。

研究組表明，由於人為氣候變化，大多數文獻記載的、大型的和影響力大的MHW的持續時間、強度和累積強度均大幅增加，出現概率已增加了20倍以上。

在工業化之前的氣候中，MHW每數百至數千年才發生一次，升溫1.5℃後預計每十年至百年發生一次，升溫3℃後預計每幾年便會發生一次。因此，制定雄心勃勃的氣候目標對於減少大量MHW影響風險是必不可少的。

▲ Abstract

Marine heatwaves (MHWs)—periods of extremely high ocean temperatures in specific regions—have occurred in all of Earth’s ocean basins over the past two decades, with severe negative impacts on marine organisms and ecosystems. However, for most individual MHWs, it is unclear to what extent they have been altered by human-induced climate change. We show that the occurrence probabilities of the duration, intensity, and cumulative intensity of most documented, large, and impactful MHWs have increased more than 20-fold as a result of anthropogenic climate change. MHWs that occurred only once every hundreds to thousands of years in the preindustrial climate are projected to become decadal to centennial events under 1.5°C warming conditions and annual to decadal events under 3°C warming conditions. Thus, ambitious climate targets are indispensable to reduce the risks of substantial MHW impacts.

化學Chemistry

Stable perovskite solar cells with efficiency exceeding 24.8% and 0.3-V voltage loss

效率超過24.8%、電壓損耗為0.3V的穩定鈣鈦礦太陽能電池

▲ 作者：Mingyu Jeong, In Woo Choi, Eun Min Go, Yongjoon Cho, Minjin Kim, Byongkyu Lee, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6511/1615

▲ 摘要

進一步改善和穩定鈣鈦礦太陽能電池（PSC）的性能對於實現下一代光伏產品的商業可行性至關重要。

考慮到氟化對共軛材料的能級、疏水性和非共價相互作用的益處，研究組開發了經典空穴傳輸材料（HTM）Spiro-OMeTAD的兩種氟化異構體，並將其用作製備PSC的HTM。

研究組通過實驗、原子分析和理論分析研究了由結構異構引起的結構-性質關係，製備的PSC效率高達24.82％（損耗僅為0.3V電壓，認證效率為24.64％），在潮溼條件下未封裝亦可保持長期穩定性（500小時後效率保持87％）。在大面積電池中也實現了22.31％的效率。

▲ Abstract

Further improvement and stabilization of perovskite solar cell (PSC) performance are essential to achieve the commercial viability of next-generation photovoltaics. Considering the benefits of fluorination to conjugated materials for energy levels, hydrophobicity, and noncovalent interactions, two fluorinated isomeric analogs of the well-known hole-transporting material (HTM) Spiro-OMeTAD are developed and used as HTMs in PSCs. The structure–property relationship induced by constitutional isomerism is investigated through experimental, atomistic, and theoretical analyses, and the fabricated PSCs feature high efficiency up to 24.82% (certified at 24.64% with 0.3-volt voltage loss), along with long-term stability in wet conditions without encapsulation (87% efficiency retention after 500 hours). We also achieve an efficiency of 22.31% in the large-area cell.

Rotational resonances in the H2CO roaming reaction are revealed by detailed correlations

詳細關聯揭示H2CO漫遊反應中的旋轉共振

▲ 作者：Mitchell S. Quinn, Klaas Nauta, Meredith J. T. Jordan, Joel M. Bowman, Paul L. Houston, Scott H. Kable, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6511/1592

▲ 摘要

自16年前被發現以來，漫遊已成為分子光化學中普遍存在的機理。人們已了解漫遊機理的一般特徵，但對於勢能面（PES）如何決定反應結果的細節仍知之甚少。研究組對甲醛（H2CO）光解離進行了詳細的實驗，並確定了分子氫和一氧化碳產物的全相關量子態分布。

這些實驗揭示了此前從未發現的雙峰一氧化碳旋轉分布。經典軌跡計算表明，當PES將反應導向順式和反式O–C–H···H臨界幾何結構時，共振引發了這些特徵，分別產生回彈和剝離機制。

這些微妙而普遍的影響在這個典型的漫遊反應中顯示出額外的複雜性，研究組希望這是普遍的，他們還為漫遊預測理論提供了詳細基準。

▲ Abstract

Since its discovery 16 years ago, roaming has become a ubiquitous mechanism in molecular photochemistry. Its general features are now understood, but little detail is known about how the potential energy surface (PES) determines reaction outcomes. We performed detailed experiments on formaldehyde (H2CO) photodissociation and determined fully correlated quantum state distributions of the molecular hydrogen and carbon monoxide products. These experiments reveal previously undetected bimodal carbon monoxide rotational distributions. Insights from classical trajectory calculations demonstrate that these features arise from resonances as the PES directs the reaction into cis and trans O–C–H···H critical geometries, which produce rebound and stripping mechanisms, respectively. These subtle and pervasive effects demonstrate additional complexity in this prototypical roaming reaction, which we expect to be general. They also provide detailed benchmarks for predictive theories of roaming.

Synthetic connectivity, emergence, and self-regeneration in the network of prebiotic chemistry

前生命化學網絡中的合成連接、出現和自我再生

▲ 作者：Agnieszka Wołos, Rafał Roszak, Anna Żądło-Dobrowolska, Wiktor Beker, Barbara Mikulak-Klucznik, Grzegorz Spólnik, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6511/eaaw1955

▲ 摘要

前生命化學的挑戰是從少數原始底物中追蹤生命關鍵組成部分的合成過程。

研究組報告了一種正向合成算法，可在一般公認的條件下從這些底物中生成一個完整的前生命化學反應網絡，包含已報導的和先前未確定的通往生物靶標的途徑，以及非生物分子的合理合成。

該網絡還表現出三種形式的非凡化學反應：網絡中的分子可充當下遊反應類型的催化劑；形成功能化學系統，包括自我再生循環；產生與生物分化的原始形式有關的表面活性劑。

為了支持這些觀點，研究組使用計算機預測了幾種生物分子的前生命合成，以及亞氨基二乙酸的多步自我再生循環。

▲ Abstract

The challenge of prebiotic chemistry is to trace the syntheses of life’s key building blocks from a handful of primordial substrates. Here we report a forward-synthesis algorithm that generates a full network of prebiotic chemical reactions accessible from these substrates under generally accepted conditions. This network contains both reported and previously unidentified routes to biotic targets, as well as plausible syntheses of abiotic molecules. It also exhibits three forms of nontrivial chemical emergence, as the molecules within the network can act as catalysts of downstream reaction types; form functional chemical systems, including self-regenerating cycles; and produce surfactants relevant to primitive forms of biological compartmentalization. To support these claims, computer-predicted, prebiotic syntheses of several biotic molecules as well as a multistep, self-regenerative cycle of iminodiacetic acid were validated by experiment.