The surface chemistry of ionic liquid-treated CsPbBr3 quantum dots.

The power conversion efficiencies of lead halide perovskite thin film solar cells have surged in the short time since their inception. Compounds, such as ionic liquids (ILs), have been explored as chemical additives and interface modifiers in perovskite solar cells, contributing to the rapid increase in cell efficiencies. However, due to the small surface area-to-volume ratio of the large grained polycrystalline halide perovskite films, an atomistic understanding of the interaction between ILs and perovskite surfaces is limited. Here, we use quantum dots (QDs) to study the coordinative surface interaction between phosphonium-based ILs and CsPbBr3. When native oleylammonium oleate ligands are exchanged off the QD surface with the phosphonium cation as well as the IL anion, a threefold increase in photoluminescent quantum yield of as-synthesized QDs is observed. The CsPbBr3 QD structure, shape, and size remain unchanged after ligand exchange, indicating only a surface ligand interaction at approximately equimolar additions of the IL. Increased concentrations of the IL lead to a disadvantageous phase change and a concomitant decrease in photoluminescent quantum yields. Valuable information regarding the coordinative interaction between certain ILs and lead halide perovskites has been elucidated and can be used for informed pairing of beneficial combinations of IL cations and anions.

Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene.

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the so-called "perfluoro effect", the resulting electronic structure and photochemical reactivity of hexafluorobenzene is still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4π-electrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ∼100 nm Stokes shift in fluorescence-in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway toward hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

Nonadiabatic Coupling Effects in the 800 nm Strong-Field Ionization-Induced Coulomb Explosion of Methyl Iodide Revealed by Multimass Velocity Map Imaging and Ab Initio Simulation Studies.

The Coulomb explosion (CE) of jet-cooled CH3I molecules using ultrashort (40 fs), nonresonant 805 nm strong-field ionization at three peak intensities (260, 650, and 1300 TW cm-2) has been investigated by multimass velocity map imaging, revealing an array of discernible fragment ions, that is, Iq+ (q ≤ 6), CHn+ (n = 0-3), CHn2+ (n = 0, 2), C3+, H+, H2+, and H3+. Complementary ab initio trajectory calculations of the CE of CH3IZ+ cations with Z ≤ 14 identify a range of behaviors. The CE of parent cations with Z = 2 and 3 can be well-described using a diatomic-like representation (as found previously) but the CE dynamics of all higher CH3IZ+ cations require a multidimensional description. The ab initio predicted Iq+ (q ≥ 3) fragment ion velocities are all at the high end of the velocity distributions measured for the corresponding Iq+ products. These mismatches are proposed as providing some of the clearest insights yet into the roles of nonadiabatic effects (and intramolecular charge transfer) in the CE of highly charged molecular cations.

Communication: Multi-mass velocity map imaging study of the ultraviolet photodissociation of dimethyl sulfide using single photon ionization and a PImMS2 sensor.

This study of the photodissociation of dimethyl sulfide at λ = 227.5 nm demonstrates the opportunities (and some of the challenges) of product detection using vacuum ultraviolet photoionization combined with recently developed multi-mass imaging methods. The capability of imaging different charged products simultaneously allows determination of the primary fragmentation dynamics through, for example, product fragment momentum and angular distribution matching and reveals potential complications from dissociative ionization, product alignment-dependent photoionization probabilities, and the effects of space charging.

Solitary drinkers in Great Britain: How do their sociodemographic characteristics, consumption patterns, and drinking occasions differ from those who drink with others?

OBJECTIVE: Inequalities in alcohol-related harm may arise partly from differences in drinking practices between population groups. One under-researched practice associated with harm is consuming alcohol alone. We identify sociodemographic characteristics associated with drinking alone and the occasion-level characteristics associated with occasions when people drink alone. METHOD: A cross-sectional analysis of one-week drinking diaries collected between 2015 and 2019 was conducted using event-level data on 271,738 drinking occasions reported by 83,952 adult drinkers in Great Britain. Our two dependent variables were a binary indicator of reporting at least one solitary drinking occasion in the diary-week at the individual-level and a binary indicator of drinking alone at the occasion-level (event-level). RESULTS: Individual-level characteristics associated with solitary drinking were being a man (OR 1.88, 95%CI [1.80,1.96]), aged over 50 (OR 2.60, 95%CI [2.40,2.81]), not in a relationship (OR 3.39, 95%CI [3.20, 3.59]), living alone (OR 2.51, 95%CI [2.37, 2.66]), and a high-risk drinker (OR 1.54, 95%CI [1.52,1.59]). Occasion-level characteristics associated with solitary drinking were that they were more likely to occur in the off-trade (OR 3.08, 95%CI [2.95,3.21]), Monday-Thursday (OR 1.36, 95%CI [1.27,1.47]), and after 10pm (OR 1.36, 95%CI [1.27,1.47]) controlling for geographic region and the month the interview took place. CONCLUSIONS: Characteristics of solitary drinking largely align with characteristics we associated with drinking problems. Those who partake in at least one solitary drinking occasion are overall more likely to consume alcohol at risky levels, however, the number of drinks consumed in each occasion was lower during a solitary drinking occasion.

High-Throughput Screening for Ultrafast Photochemical Reaction Discovery.

High-repetition-rate lasers present an opportunity to extend ultrafast spectroscopy from a detailed probe of singular model photochemical systems to a routine analysis technique in training machine learning models to aid the design cycle of photochemical syntheses. We bring together innovations in line scan cameras and micro-electro-mechanical grating modulators with sample delivery via high-pressure liquid chromatography pumps to demonstrate a transient absorption spectrometer that can characterize photoreactions initiated with ultrashort ultraviolet pulses in a time scale of minutes. Furthermore, we demonstrate that the ability to rapidly screen an important class of photochemical system, pyrimidine nucleosides, can be used to explore the effect of conformational modification on the evolution of excited-state processes.

Recovery From Severe Mental Health Problems: A Systematic Review of Service User and Informal Caregiver Perspectives.

Introduction: The recovery approach aims to have users' perspectives at the heart of service development and research; it is a holistic perspective that considers social needs, personal growth and inclusion. In the last decade recovery-oriented research and practice has increased greatly, however, a comprehensive model of recovery considering exclusively the perspectives of people with lived experience has not been devised. Aims: This review aimed to develop a framework and contextualize service users' and informal caregivers' understanding of recovery from severe mental health problems. Methods: We systematically searched 6 databases including key terms related to knowledge, experience and narratives AND mental health AND personal recovery. The search was supplemented with reference sourcing through gray literature, reference tracking and expert consultation. Data analysis consisted of a qualitative meta-synthesis using constant comparative methods. Results: Sixty-two studies were analyzed. A pattern emerged regarding the recovery paradigms that the studies used to frame their findings. The resulting recovery framework included the domains Social recovery; Prosperity (Legal, political, and economic recovery); Individual Recovery; and Clinical Recovery Experience (SPICE). Service users' definitions of recovery tended to prioritize social aspects, particularly being accepted and connecting with others, while caregivers focused instead on clinical definitions of recovery such as symptom remission. Both groups emphasized individual aspects such as becoming self-sufficient and achieving personal goals, which was strongly linked with having economic means for independence. Conclusions: The recovery model provided by this review offers a template for further research in the field and a guide for policy and practice. Predominant definitions of recovery currently reflect understandings of mental health which focus on an individual perspective, while this review found an important emphasis on socio-political aspects. At the same time, only a small number of studies took place in low-income countries, focused on minoritized populations, or included caregivers' perspectives. These are important gaps in the literature that require further attention. Systematic Review Registration: The review protocol was registered on PROSPERO (CRD42017076450); https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=76450.

Ultraviolet photochemistry of ethane: implications for the atmospheric chemistry of the gas giants.

Chemical processing in the stratospheres of the gas giants is driven by incident vacuum ultraviolet (VUV) light. Ethane is an important constituent in the atmospheres of the gas giants in our solar system. The present work describes translational spectroscopy studies of the VUV photochemistry of ethane using tuneable radiation in the wavelength range 112 ≤ λ ≤ 126 nm from a free electron laser and event-triggered, fast-framing, multi-mass imaging detection methods. Contributions from at least five primary photofragmentation pathways yielding CH2, CH3 and/or H atom products are demonstrated and interpreted in terms of unimolecular decay following rapid non-adiabatic coupling to the ground state potential energy surface. These data serve to highlight parallels with methane photochemistry and limitations in contemporary models of the photoinduced stratospheric chemistry of the gas giants. The work identifies additional photochemical reactions that require incorporation into next generation extraterrestrial atmospheric chemistry models which should help rationalise hitherto unexplained aspects of the atmospheric ethane/acetylene ratios revealed by the Cassini-Huygens fly-by of Jupiter.

Quantifying rival bond fission probabilities following photoexcitation: C-S bond fission in t-butylmethylsulfide.

We illustrate a new, collision-free experimental strategy that allows determination of the absolute probabilities of rival bond fission processes in a photoexcited molecule - here t-butylmethylsulfide (BSM). The method combines single photon ('universal') ionization laser probe methods, simultaneous imaging of all probed fragments (multi-mass ion imaging) and the use of an appropriate internal calibrant (here dimethylsulfide). Image analysis allows quantification of the dynamics of the rival B-SM and BS-M bond fission processes following ultraviolet (UV) excitation of BSM and shows the former to be twice as probable, despite the only modest (∼2%) differences in the respective ground state equilibrium C-S bond lengths or bond strengths. Rationalising this finding should provide a stringent test of the two close-lying, coupled excited states of 1A'' symmetry accessed by UV excitation in BSM and related thioethers, of the respective transition dipole moment surfaces, and of the geometry dependent non-adiabatic couplings that enable the rival C-S bond fissions.

Exploring the Dynamics of the Photoinduced Ring-Opening of Heterocyclic Molecules.

Excited states formed by electron promotion to an antibonding σ* orbital are now recognized as key to understanding the photofragmentation dynamics of a broad range of heteroatom containing small molecules: alcohols, thiols, amines, and many of their aromatic analogues. Such excited states may be populated by direct photoexcitation, or indirectly by nonadiabatic transfer of population from some other optically excited state (e.g., a ππ* state). This Perspective explores the extent to which the fast-growing literature pertaining to such (n/π)σ*-state mediated bond fissions can inform and enhance our mechanistic understanding of photoinduced ring-opening in heterocyclic molecules.