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We theoretically investigate the ionization of neonlike atoms by an intense ultrashort circularly polarized laser pulse as a function of wavelength, spanning the regime from single-photon ionization to multiphoton and tunneling ionization. In order to determine the dependence of the ionization probabilities on the magnetic quantum number of the initial state, we perform ab initio numerical calculations of the corresponding time-dependent Schr\"odinger equation in the single-active-electron approximation. Specific emphasis of our analysis is given to the intermediate-wavelength regime of about 50 nm to 300 nm, in which the trend in the ionization probability of counterrotating electrons strongly differs from those for electrons in the other two initial magnetic sublevels. Theoretical analysis and numerical results indicate that the enhanced emission of counterrotating electrons occurs via photon absorption channels, which are only accessible for electrons rotating opposite to the rotation direction of the external electric field. Physical mechanisms behind the enhancement are identified as threshold effects, in which the emission into continuum states with low angular momentum quantum numbers is favored, and resonant enhanced ionization involving transitions via specific excited states in the atom. Numerical results showing the strong population in the relevant excited states, specifically those with low angular momentum quantum number, for the ionization of counterrotating electrons, and the overall similar trends in ionization and excitation for electrons with the other two initial magnetic quantum numbers support our interpretation. Overall, these effects lead to a change in the ionization ratio of co- to counterrotating electrons by two orders of magnitude from 10:1 to 1:10. This strong selectivity in the emission of electrons may lead to new opportunities in the generation of ultrashort spin-polarized electron pulses.

Characterization of ultrashort vacuum and deep ultraviolet pulses is important in view of applications of those pulses for spectroscopic and dynamical imaging of atoms, molecules, and materials. We present an extension of the autocorrelation technique, applied for measurement of the pulse duration via a single Gaussian function. Analytic solutions for two-photon ionization of atoms by Gaussian pulses are used along with an expansion of the pulse to be characterized using multiple Gaussians at multi-color central frequencies. This approach allows one to use two-photon autocorrelation signals to characterize isolated ultrashort pulses and pulse trains, i.e., the time-dependent amplitude and phase variation of the electric field. The potential of the method is demonstrated using vacuum and deep ultraviolet pulses and pulse trains obtained from numerical simulations of macroscopic high harmonic spectra.

We present results of a theoretical study on how one can infer the time- dependent amplitude and phase variation of the electric field of a vacuum ultraviolet pulse from autocorrelation ionization measurements.

With unprecedented losses in biodiversity, the need for stronger environmental policy has emerged as a conservation priority. Yet recovery planning for imperiled species remains a cumbersome, slow legislative process. In the present article, we examine features of recovery planning for species listed under Canada's Species at Risk Act to determine those influencing recovery planning duration. We found that the time to completion of recovery strategies increases with the number of jurisdictions concurrently listing the species, greater land tenure diversity, species population size, and road density. Species at risk in Canada with no listing status in the United States also suffered longer delays. To achieve a more efficient, timely, and defensible implementation of recovery planning, we recommend that governments prioritize recovery planning on the basis of risk level, promote transjurisdictional collaboration among listing agencies, anticipate and mitigate conservation challenges associated with multitenured and developed landscapes, and adopt procedures that enhance compliance with legislated timelines for recovery planning.

Summary Energetic balance is a central driver of individual survival and population change, yet estimating energetic costs in free- and wide-ranging animals presents a significant challenge. Animal-borne activity monitors (using accelerometer technology) present a promising method of meeting this challenge and open new avenues for exploring energetics in natural settings. To determine the behaviours and estimated energetic costs associated with a given activity level, three captive reindeer (Rangifer tarandus tarandus) at the Toronto Zoo were fitted with collars and observed for 53 h. Activity patterns were then measured over 13 months for 131 free-ranging woodland caribou (R. t. caribou) spanning 450 000 km2 in northern Ontario. The captive study revealed a positive but decelerating relationship between activity level and energetic costs inferred from previous behavioural studies. Field-based measures of activity were modelled against individual displacement, vegetation abundance (Normalized Difference Vegetation Index), snow depth and temperature, and the best fit model included all parameters and explained over half of the variation in the data. Individual displacement was positively related to activity levels, suggesting that broad differences in energetic demands are influenced by variation in movement rates. After accounting for displacement, activity was highest at intermediate levels of vegetation abundance, presumably due to foraging behaviour. Snow depth, probably associated with digging for winter forage, moderately increased activity. Activity levels increased significantly at the coldest winter temperatures, suggesting the use of behavioural thermoregulation by caribou. These interpretations of proximate causal factors should be regarded as hypotheses subject to validation under normal field conditions. These results illustrate the landscape characteristics that increase energetic demands for caribou and confirm the great potential for the use of accelerometry in studies of animal energetics.