Site-specific probing of charge transfer dynamics in organic photovoltaics

We report the site-specific probing of charge-transfer dynamics in a prototype system for organic photovoltaics (OPV) by picosecond time-resolved X-ray photoelectron spectroscopy. A layered system consisting of approximately two monolayers of C$_{60}$ deposited on top of a thin film of Copper-Phthalocyanine (CuPC) is excited by an optical pump pulse and the induced electronic dynamics are probed with 590 eV X-ray pulses. Charge transfer from the electron donor (CuPC) to the acceptor (C$_{60}$) and subsequent charge carrier dynamics are monitored by recording the time-dependent C 1$s$ core level photoemission spectrum of the system. The arrival of electrons in the C$_{60}$ layer is readily observed as a completely reversible, transient shift of the C$_{60}$ associated C 1$s$ core level, while the C 1$s$ level of the CuPC remains unchanged. The capability to probe charge transfer and recombination dynamics in OPV assemblies directly in the time domain and from the perspective of well-defined domains is expected to open additional pathways to better understand and optimize the performance of this emerging technology

Incidence of acute lower respiratory tract disease hospitalisations, including pneumonia, among adults in Bristol, UK, 2019, estimated using both a prospective and retrospective methodology

OBJECTIVES: To determine the disease burden of acute lower respiratory tract disease (aLRTD) and its subsets (pneumonia, lower respiratory tract infection (LRTI) and heart failure) in hospitalised adults in Bristol, UK. SETTING: Single-centre, secondary care hospital, Bristol, UK. DESIGN: We estimated aLRTD hospitalisations incidence in adults (≥18 years) in Bristol, UK, using two approaches. First, retrospective International Classification of Diseases 10th revision (ICD-10) code analysis (first five positions/hospitalisation) identified aLRTD events over a 12-month period (March 2018 to February 2019). Second, during a 21-day prospective review (19 August 2019 to 9 September 2019), aLRTD admissions were identified, categorised by diagnosis and subsequently annualised. Hospital catchment denominators were calculated using linked general practice and hospitalisation data, with each practice’s denominator contribution calculated based on practice population and per cent of the practices’ hospitalisations admitted to the study hospital. PARTICIPANTS: Prospective review: 1322 adults screened; 410 identified with aLRTD. Retrospective review: 7727 adult admissions. PRIMARY AND SECONDARY OUTCOME MEASURES: The incidence of aLRTD and its subsets in the adult population of Southmead Hospital, Bristol UK. RESULTS: Based on ICD-10 code analysis, annual incidences per 100 000 population were: aLRTD, 1901; pneumonia, 591; LRTI, 739; heart failure, 402. aLRTD incidence was highest among those ≥65 years: 65–74 (3684 per 100 000 adults), 75–84 (6962 per 100 000 adults) and ≥85 (11 430 per 100 000 adults). During the prospective review, 410/1322 (31%) hospitalised adults had aLRTD signs/symptoms and annualised incidences closely replicated retrospective analysis results. CONCLUSIONS: The aLRTD disease burden was high, increasing sharply with age. The aLRTD incidence is probably higher than estimated previously due to criteria specifying respiratory-specific symptoms or radiological change, usage of only the first diagnosis code and mismatch between case count sources and population denominators. This may have significant consequences for healthcare planning, including usage of current and future vaccinations against respiratory infection

Probing ultrafast C-Br bond fission in the UV photochemistry of bromoform with core-to-valence transient absorption spectroscopy.

UV pump-extreme UV (XUV) probe femtosecond transient absorption spectroscopy is used to study the 268 nm induced photodissociation dynamics of bromoform (CHBr3). Core-to-valence transitions at the Br(3d) absorption edge (∼70 eV) provide an atomic scale perspective of the reaction, sensitive to changes in the local valence electronic structure, with ultrafast time resolution. The XUV spectra track how the singly occupied molecular orbitals of transient electronic states develop throughout the C-Br bond fission, eventually forming radical Br and CHBr2 products. Complementary ab initio calculations of XUV spectral fingerprints are performed for transient atomic arrangements obtained from sampling excited-state molecular dynamics simulations. C-Br fission along an approximately CS symmetrical reaction pathway leads to a continuous change of electronic orbital characters and atomic arrangements. Two timescales dominate changes in the transient absorption spectra, reflecting the different characteristic motions of the light C and H atoms and the heavy Br atoms. Within the first 40 fs, distortion from C3v symmetry to form a quasiplanar CHBr2 by the displacement of the (light) CH moiety causes significant changes to the valence electronic structure. Displacement of the (heavy) Br atoms is delayed and requires up to ∼300 fs to form separate Br + CHBr2 products. We demonstrate that transitions between the valence-excited (initial) and valence + core-excited (final) state electronic configurations produced by XUV absorption are sensitive to the localization of valence orbitals during bond fission. The change in valence electron-core hole interaction provides a physical explanation for spectral shifts during the process of bond cleavage

Cardiovascular safety of mometasone/indacaterol and mometasone/indacaterol/glycopyrronium once-daily fixed-dose combinations in asthma:pooled analysis of phase 3 trials

OBJECTIVE: To evaluate cardiovascular safety of two new inhaled fixed-dose combinations for treatment of asthma: (i) the inhaled corticosteroid/long-acting beta2-agonist (ICS/LABA) mometasone furoate/indacaterol acetate (MF/IND), (ii) the ICS/LABA/long-acting muscarinic antagonist (LAMA) MF/IND/glycopyrronium bromide (GLY). METHODS: Patient-level data were pooled from four randomized trials, including 52-week studies PALLADIUM (n = 2216) and IRIDIUM (n = 3092), 24-week study ARGON (n = 1426), and 12-week study QUARTZ (n = 802). Cardio-/cerebrovascular (CCV) event frequencies were examined in the following comparisons: (1) LABA effect: pooled-dose MF/IND vs. pooled-dose MF; (2) LAMA effect: pooled-dose MF/IND/GLY vs. pooled-dose MF/IND; (3) ICS-dose effects: (a) high-dose MF/IND vs. medium-dose MF/IND, (b) high-dose MF/IND/GLY vs. medium-dose MF/IND/GLY; (4) intra-class effects: (a) high-dose MF/IND vs. Fluticasone/Salmeterol (F/S), (b) high-dose MF/IND/GLY vs. F/S + Tiotropium (TIO). Risk estimates (percentage of patients with ≥1 CCV event) and risk differences (RDs) with 95% confidence intervals (CIs) were calculated for each comparison. RESULTS: The frequency of CCV events was low, without notable differences between comparison groups. Risk estimates and corresponding RDs (95% CIs) were as follows: (1) pooled-dose MF/IND = 2.35%, pooled-dose MF = 2.18%, RD = 0.17% (-1.00%, 1.34%); (2) pooled-dose MF/IND/GLY = 3.65%, pooled-dose MF/IND = 3.77%, RD = -0.12% (-1.63%, 1.39%); (3a) high-dose MF/IND = 3.69%, medium-dose MF/IND = 3.35%, RD = 0.34% (-1.25%, 1.94%); (3b) high-dose MF/IND/GLY = 2.84%, medium-dose MF/IND/GLY = 2.02%, RD = 0.82% (-0.49%, 2.13%); (4a) high-dose MF/IND = 3.69%, F/S = 2.82%, RD = 0.87% (-0.66%, 2.40%); (4b) high-dose MF/IND/GLY = 1.26%, F/S + TIO = 1.05%, RD = 0.21% (-1.26%, 1.68%). CONCLUSIONS: There was no evidence of increased cardiovascular risk attributable to the addition of IND to MF or addition of GLY to MF/IND. Similarly, no evidence of increased cardiovascular risk was observed with an increase in the ICS-dose or relative to F/S ± TIO

New insights into the laser-assisted photoelectric effect from solid-state surfaces

Photoemission from a solid surface provides a wealth of information about the electronic structure of the surface and its dynamic evolution. Ultrafast pump-probe experiments are particularly useful to study the dynamic interactions of photons with surfaces as well as the ensuing electron dynamics induced by these interactions. Time-resolved laser-assisted photoemission (tr-LAPE) from surfaces is a novel technique to gain deeper understanding of the fundamentals underlying the photoemission process. Here, we present the results of a femtosecond time-resolved soft X-ray photoelectron spectroscopy experiment on two different metal surfaces conducted at the X-ray Free-Electron Laser FLASH in Hamburg. We study photoemission from the W 4f and Pt 4f core levels using ultrashort soft X-ray pulses in combination with synchronized infrared (IR) laser pulses. When both pulses overlap in time and space, laser-assisted photoemission results in the formation of a series of sidebands that reflect the dynamics of the laser-surface interaction. We demonstrate a qualitatively new level of sideband generation up to the sixth order and a surprising material dependence of the number of sidebands that has so far not been predicted by theory. We provide a semi-quantitative explanation of this phenomenon based on the different dynamic dielectric responses of the two materials. Our results advance the understanding of the LAPE process and reveal new details of the IR field present in the surface region, which is determined by the dynamic interplay between the IR laser field and the dielectric response of the metal surfaces.Comment: 18 pages, 3 figure

Angular momentum in rotating superfluid droplets

The angular momentum of rotating superfluid droplets originates from quantized vortices and capillary waves, the interplay between which remains to be uncovered. Here, the rotation of isolated submicrometer superfluid 4He droplets is studied by ultrafast x-ray diffraction using a free electron laser. The diffraction patterns provide simultaneous access to the morphology of the droplets and the vortex arrays they host. In capsule-shaped droplets, vortices form a distorted triangular lattice, whereas they arrange along elliptical contours in ellipsoidal droplets. The combined action of vortices and capillary waves results in droplet shapes close to those of classical droplets rotating with the same angular velocity. The findings are corroborated by density functional theory calculations describing the velocity fields and shape deformations of a rotating superfluid cylinder