Benchmark nonperturbative calculations for the electron-impact ionization of Li(2s) and Li(2p)

Three independent nonperturbative calculations are reported for the electron-impact ionization of both the ground and first excited states of the neutral lithium atom. The time-dependent close-coupling, the R matrix with pseudostates, and the converged close-coupling methods yield total integral cross sections that are in very good agreement with each other, while perturbative distorted-wave calculations yield cross sections that are substantially higher. These nonperturbative calculations provide a benchmark for the continued development of electron-atom experimental methods designed to measure both ground and excited state ionization

Unsustainable fuelwood extraction from South African savannas

Wood and charcoal supply the majority of sub-Saharan Africa’s rural energy needs. The long-term supply of fuelwood is in jeopardy given high consumption rates. Using airborne light detection and ranging (LiDAR), we mapped and investigated savanna aboveground biomass across contrasting land uses, ranging from densely populated communal areas to highly protected areas in the Lowveld savannas of South Africa. We combined the LiDAR observations with socio-economic data, biomass production rates and fuelwood consumption rates in a supply–demand model to predict future fuelwood availability. LiDAR-based biomass maps revealed disturbance gradients around settlements up to 1.5 km, corresponding to the maximum distance walked to collect fuelwood. At current levels of fuelwood consumption (67% of households use fuelwood exclusively, with a 2% annual reduction), we calculate that biomass in the study area will be exhausted within thirteen years. We also show that it will require a 15% annual reduction in consumption for eight years to a level of 20% of households using fuelwood before the reduction in biomass appears to stabilize to sustainable levels. The severity of dwindling fuelwood reserves in African savannas underscores the importance of providing affordable energy for rural economic development.The CSIR researchers were funded by the CSIR Strategic Research Panel and the Department of Science and Technology’s Earth Observation Unit. SUCSES study (Sustainability in Communal Socio-Ecological Systems) which provided data on fuelwood use in Justicia was funded by the South African National Research Foundation. The airborne campaign and analysis was funded by the Andrew Mellon Foundation.http://iopscience.iop.org/1748-9326am201

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

Application of the time-dependent close-coupling approach to few-body atomic and molecular ionizing collisions

We review the recent progress made in applying the time-dependent close-coupling approach to ionizing collisions of electrons, photons, and ions with small atoms and molecules. The last twenty years have seen a proliferation of non-perturbative approaches applied to fundamental atomic and molecular scattering processes. Such processes form the building blocks of describing the dynamics of plasmas over a wide range of temperatures and densities, and also provide insight into the long-range Coulomb interactions between charged particles. Studies of the few-body Coulomb problem presented in electron, photon, or ion-impact ionization of small atoms and molecules, by direct solution of the time-dependent Schrödinger equation, are particularly useful because the complicated three-body boundary conditions of more than one continuum particle in a Coulomb potential are not required. With the continuing growth and increasing availability of high-performance computing resources, such methods can now be applied to a wide variety of scattering processes. The recent progress made using such a time-dependent approach is described in this colloquium. In this paper, we focus on the recent results obtained for one-, two-, and three-electron systems, thus building on a previous review of the time-dependent close-coupling method [M.S. Pindzola et al., J. Phys. B 40, R39 (2007)], which also described the application to multi-electron targets

Dielectronic recombination data for dynamic finite-density plasmas - v. the lithium isoelectronic sequence

Dielectronic recombination data for the lithium isoelectronic sequence has been calculated as part of the assembly of a dielectronic recombination database necessary for modelling of dynamic finite-density plasmas (Badnell et al. 2003). Dielectronic recombination coefficients for a selection of ions from this sequence are presented and the results discussed

Diagnosing bitter pit in apple during storage by chlorophyll fluorescence as a non-destructive Tool

Bitter pit is an important physiological disorder of apple that can develop on the tree but is most prevalent during storage. Delaying fruit maturation after harvest through controlled atmosphere storage and application of 1-MCP SmartFreshTM) can delay the onset of symptoms; however, significant losses may occur in long-term stored apples. It is hard to detect internal bitter pit using external examination alone. Current predictive methods are based on destructive internal quality assessments and mineral analysis. A non-destructive method to detect and predict the propensity of fruit to develop bitter pit at harvest and during the early stages of storage would improve store management practices. High risk ‘Bramley’ orchards were identified from over 100 orchards surveyed across the south east of UK in 2010/11. A subsample of susceptible orchards with fruit that consistently developed bitter pit in storage as well as orchards where fruit remained free from problems were selected. Trials were conducted over two consecutive seasons (2012/13 and 2013/14) to evaluate changes of chlorophyll fluorescence in SmartFreshTM treated and untreated ‘Bramley’ apples during storage. The relationship between chlorophyll fluorescence profiles and bitter pit incidence were similar in the presence or absence of SmartFreshTM. In the early stages of storage, the chlorophyll fluorescence profiles were able to distinguish between SmartFreshTM treated and untreated samples and correlated well with fruit maturity, rate of ethylene production and onset of bitter pit; however, they were less discriminatory in determining the severity of bitter pit in long-term storage. The most discriminant chlorophyll fluorescence characteristics correlated to bitter pit were identified. Models have been developed to predict the likely incidence and development of bitter pit during storage, although they are not capable of estimating severity of the disorder

Interference effects in L-shell atomic double photoionization

Angular correlation pattern in two-electron continuum is very similar in double photoionization (DPI) of a neutral atom γ + A → A2+ + 2e- and electron-impact ionization of the corresponding singly charged ion e- + A+ → A2+ + 2e-. This allows us to i

Kinetic Energy Release Effects on the Angular Disributions from the Photoionization of H+2

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