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1. Molecular understanding of new-particle formation from <i>α</i>-pinene between −50 and +25 °C

   https://doi.org/10.5194/acp-20-9183-2020  

   Simon, Mario ; Dada, Lubna ; Heinritzi, Martin ; Scholz, Wiebke ; Stolzenburg, Dominik ; Fischer, Lukas ; Wagner, Andrea C. ; Kürten, Andreas ; Rörup, Birte ; He, Xu-Cheng ; et al ( January 2020 , Atmospheric Chemistry and Physics)

   Abstract. Highly oxygenated organic molecules (HOMs) contributesubstantially to the formation and growth of atmospheric aerosol particles,which affect air quality, human health and Earth's climate. HOMs are formedby rapid, gas-phase autoxidation of volatile organic compounds (VOCs) suchas α-pinene, the most abundant monoterpene in the atmosphere. Due totheir abundance and low volatility, HOMs can play an important role innew-particle formation (NPF) and the early growth of atmospheric aerosols,even without any further assistance of other low-volatility compounds suchas sulfuric acid. Both the autoxidation reaction forming HOMs and theirNPF rates are expected to be strongly dependent ontemperature. However, experimental data on both effects are limited.Dedicated experiments were performed at the CLOUD (Cosmics Leaving OUtdoorDroplets) chamber at CERN to address this question. In this study, we showthat a decrease in temperature (from +25 to −50 ∘C) results ina reduced HOM yield and reduced oxidation state of the products, whereas theNPF rates (J1.7 nm) increase substantially.Measurements with two different chemical ionization mass spectrometers(using nitrate and protonated water as reagent ion, respectively) providethe molecular composition of the gaseous oxidation products, and atwo-dimensional volatility basis set (2D VBS) model provides their volatilitydistribution. The HOM yield decreases with temperature from 6.2 % at 25 ∘C to 0.7 % at −50 ∘C. However, there is a strongreductionmore »of the saturation vapor pressure of each oxidation state as thetemperature is reduced. Overall, the reduction in volatility withtemperature leads to an increase in the nucleation rates by up to 3orders of magnitude at −50 ∘C compared with 25 ∘C. Inaddition, the enhancement of the nucleation rates by ions decreases withdecreasing temperature, since the neutral molecular clusters have increasedstability against evaporation. The resulting data quantify how the interplaybetween the temperature-dependent oxidation pathways and the associatedvapor pressures affect biogenic NPF at the molecularlevel. Our measurements, therefore, improve our understanding of purebiogenic NPF for a wide range of tropospherictemperatures and precursor concentrations.« less
2. Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units

   https://doi.org/10.1039/c7py01790a  

   Adachi, Yohei ; Ooyama, Yousuke ; Ren, Yi ; Yin, Xiaodong ; Jäkle, Frieder ; Ohshita, Joji ( January 2018 , Polymer Chemistry)

   Conjugated polymers composed of tricoordinate boron and π-conjugated units possess extended conjugation with relatively low-lying LUMOs arising from p B –π interactions. However, donor–acceptor (D–A) polymers that feature triorganoboranes alternating with highly electron-rich donors remain scarce. We present here a new class of hybrid D–A polymers that combine electron-rich dithienosiloles or dithienogermoles with highly robust tricoordinate borane acceptors. Polymers of modest to high molecular weight are readily prepared by Pd-catalyzed Stille coupling reaction of bis(halothienyl)boranes and distannyldithienosiloles or -germoles. The polymers are obtained as dark red solids that are stable in air and soluble in common organic solvents. Long wavelength UV-vis absorptions at ca. 500–550 nm indicate effective π-conjugation and pronounced D–A interactions along the backbone. The emission maxima occur at wavelengths longer than 600 nm in solution and experience further shifts to lower energy with increasing solvent polarity, indicative of strong intramolecular charge transfer (ICT) character of the excited state. The powerful acceptor character of the borane comonomer units in the polymer structures is also evident from cyclic voltammetry (CV) analyses that reveal relatively low-lying LUMO levels of the polymers, enhancing the D–A interaction. Density functional theory (DFT) calculations on model oligomers further support these experimental observations.
3. Artificial intelligence-enhanced quantum chemical method with broad applicability

   https://doi.org/10.1038/s41467-021-27340-2  

   Zheng, Peikun ; Zubatyuk, Roman ; Wu, Wei ; Isayev, Olexandr ; Dral, Pavlo O. ( December 2021 , Nature Communications)

   Abstract High-level quantum mechanical (QM) calculations are indispensable for accurate explanation of natural phenomena on the atomistic level. Their staggering computational cost, however, poses great limitations, which luckily can be lifted to a great extent by exploiting advances in artificial intelligence (AI). Here we introduce the general-purpose, highly transferable artificial intelligence–quantum mechanical method 1 (AIQM1). It approaches the accuracy of the gold-standard coupled cluster QM method with high computational speed of the approximate low-level semiempirical QM methods for the neutral, closed-shell species in the ground state. AIQM1 can provide accurate ground-state energies for diverse organic compounds as well as geometries for even challenging systems such as large conjugated compounds (fullerene C 60 ) close to experiment. This opens an opportunity to investigate chemical compounds with previously unattainable speed and accuracy as we demonstrate by determining geometries of polyyne molecules—the task difficult for both experiment and theory. Noteworthy, our method’s accuracy is also good for ions and excited-state properties, although the neural network part of AIQM1 was never fitted to these properties.
4. Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor

   https://doi.org/10.1038/s41467-022-30801-x  

   Dobryden, Illia ; Korolkov, Vladimir V. ; Lemaur, Vincent ; Waldrip, Matthew ; Un, Hio-Ieng ; Simatos, Dimitrios ; Spalek, Leszek J. ; Jurchescu, Oana D. ; Olivier, Yoann ; Claesson, Per M. ; et al ( June 2022 , Nature Communications)

   The field of organic electronics has profited from the discovery of new conjugated semiconducting polymers that have molecular backbones which exhibit resilience to conformational fluctuations, accompanied by charge carrier mobilities that routinely cross the 1 cm²/Vs benchmark. One such polymer is indacenodithiophene-co-benzothiadiazole. Previously understood to be lacking in microstructural order, we show here direct evidence of nanosized domains of high order in its thin films. We also demonstrate that its device-based high-performance electrical and thermoelectric properties are not intrinsic but undergo rapid stabilization following a burst of ambient air exposure. The polymer’s nanomechanical properties equilibrate on longer timescales owing to an orthogonal mechanism; the gradual sweating-out of residual low molecular weight solvent molecules from its surface. We snapshot the quasistatic temporal evolution of the electrical, thermoelectric and nanomechanical properties of this prototypical organic semiconductor and investigate the subtleties which play on competing timescales. Our study documents the untold and often overlooked story of a polymer device’s dynamic evolution toward stability.
5. The ELFIN Mission

   https://doi.org/10.1007/s11214-020-00721-7  

   Angelopoulos, V. ; Tsai, E. ; Bingley, L. ; Shaffer, C. ; Turner, D. L. ; Runov, A. ; Li, W. ; Liu, J. ; Artemyev, A. V. ; Zhang, X.-J. ; et al ( August 2020 , Space Science Reviews)

   Abstract The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or heretoforth simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar (∼93 ∘ inclination), nearly circular, low-Earth (∼450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (T orbit ∼ 90 min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50 keV to 5 MeV electrons with $\Delta $ Δ E/E < 40% and a fluxgate magnetometer (FGM) on a ∼72 cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC tomore »5 Hz Nyquist (nominally) with <0.3 nT/sqrt(Hz) noise at 1 Hz. The spinning satellites (T spin $\,\sim $ ∼ 3 s) are equipped with magnetorquers (air coils) that permit spin-up or -down and reorientation maneuvers. Using those, the spin axis is placed normal to the orbit plane (nominally), allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250 keV – 5 MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018 and launched by the ELaNa XVIII program on a Delta II rocket (with IceSatII as the primary). Mission operations are currently funded by NASA. Working under experienced UCLA mentors, with advice from The Aerospace Corporation and NASA personnel, more than 250 undergraduates have matured the ELFIN implementation strategy; developed the instruments, satellite, and ground systems and operate the two satellites. ELFIN’s already high potential for cutting-edge science return is compounded by concurrent equatorial Heliophysics missions (THEMIS, Arase, Van Allen Probes, MMS) and ground stations. ELFIN’s integrated data analysis approach, rapid dissemination strategies via the SPace Environment Data Analysis System (SPEDAS), and data coordination with the Heliophysics/Geospace System Observatory (H/GSO) optimize science yield, enabling the widest community benefits. Several storm-time events have already been captured and are presented herein to demonstrate ELFIN’s data analysis methods and potential. These form the basis of on-going studies to resolve the primary mission science objective. Broad energy precipitation events, precipitation bands, and microbursts, clearly seen both at dawn and dusk, extend from tens of keV to >1 MeV. This broad energy range of precipitation indicates that multiple waves are providing scattering concurrently. Many observed events show significant backscattered fluxes, which in the past were hard to resolve by equatorial spacecraft or non-pitch-angle-resolving ionospheric missions. These observations suggest that the ionosphere plays a significant role in modifying magnetospheric electron fluxes and wave-particle interactions. Routine data captures starting in February 2020 and lasting for at least another year, approximately the remainder of the mission lifetime, are expected to provide a very rich dataset to address questions even beyond the primary mission science objective.« less