Marc D. Davidson

Excess-photon detachment of negative chlorine ions with 100 fs laser pulses

Multiphoton detachment spectra of Cl-, showing excess-photon absorption, have been obtained using short (100 fs) and intense (up to 5*1016 W m-2) optical pulses with a wavelength of 620 nm. In the short-pulse regime the shifts in the electron spectrum can be related directly to shifts of the continuum states. In this way, it is shown experimentally that excess-photon detachment can occur in the absence of channel closure.

Monetary Valuation of Emissions in Implementing Environmental Policy

At various levels of environmental policy making there is a demand to translate polluting emissions into monetary units. In the so‐called reduction cost approach, based upon policy targets, polluting emissions are expressed in monetary terms by determination of the marginal unit reduction cost at the emission target level. This approach provides shadow prices for emissions by which it can be established whether a certain measure or technology belongs to the most efficient set of measures by which the policy targets can be reached. This article argues that, if clear (generic) government targets such as national emission reduction targets exist for an emission, shadow prices derived by this method are to be preferred to shadow prices derived by other methods for decisions at the project (implementation) level. By application of the reduction cost approach, implementation decisions can be made that are both cost‐effective and consistent with government policy.

Strong biotic influences on regional patterns of climate regulation services

Climate regulation services from forests are an important leverage in global-change mitigation treaties. Like most ecosystem services, climate regulation is the product of various ecological phenomena with unique spatial features. Elucidating which abiotic and biotic factors relate to spatial patterns of climate regulation services advances our understanding of what underlies climate-mitigation potential and its variation within and across ecosystems. Here we quantify and contrast the statistical relations between climate regulation services (albedo and evapotranspiration, primary productivity, and soil carbon) and abiotic and biotic factors. We focus on 16,955 forest plots in a regional extent across the eastern United States. We find the statistical effects of forest litter and understory carbon on climate regulation services to be as strong as those of temperature-precipitation interactions. These biotic factors likely influence climate regulation through changes in vegetation and canopy density, radiance scattering, and decomposition rates. We also find a moderate relation between leaf nitrogen traits and primary productivity at this regional scale. The statistical relation between climate regulation and temperature-precipitation ranges, seasonality, and climatic thresholds highlights a strong feedback with global climate change. Our assessment suggests the expression of strong biotic influences on climate regulation services at a regional, temperate extent. Biotic homogenization and management practices manipulating forest structure and succession will likely strongly impact climate-mitigation potential. The identity, strength, and direction of primary influences differed for each process involved in climate regulation. Hence, different abiotic and biotic factors are needed to monitor and quantify the full climate-mitigation potential of temperate forest ecosystems.

Rights to Ecosystem Services

Ecosystem services are the benefits people obtain from ecosystems. Many of these services are provided outside the borders of the land where they are produced; this article investigates who is entitled to these non-excludable ecosystem services from two libertarian perspectives. Taking a right-libertarian perspective, it is concluded that the beneficiaries generally hold the right to use non-excludable ecosystem services and the right that landowners do not convert ecosystems; landowners are only at liberty to convert ecosystems if they appropriated their land before any beneficiary used the services and converted the ecosystems before or shortly after the beneficiaries started using the services. This means that the beneficiaries generally have the right to compensation payments by the landowners in the event of service losses, instead of the landowners having the right to payments for ecosystem services by the beneficiaries. Taking a left-libertarian perspective, it is concluded that people hold an equal per capita right to non-excludable ecosystem services. This right can be secured by the beneficiaries paying a central authority for the non-excludable ecosystem services they use, while the owners of the land on which the ecosystems are situated pay a central authority for the non-excludable ecosystem services lost as a result of their activities. The central authority distributes the returns to the community on an equal per capita basis.

Measurements on the quantum defect of the2S Rydberg series and fine structure of the2D Rydberg series in the gallium I spectrum

Level positions of members betweenn=25 andn=45 of the2S Rydberg series in Ga I were measured with high accuracy. The quantum defect of this series turns out to be constant over the region observed, indicating an unperturbed series. The value of the quantum defect is 2.791(2). The fine structure in the2D series was measured by using direct excitation. A qualitative explanation is given.

Do payments for forest ecosystem services generate double dividends? An integrated impact assessment of Vietnam’s PES program

Payments for ecosystem services (PES) often serve multiple objectives, such as carbon emission reduction and poverty alleviation. However, the effectiveness of PES as an instrument to achieve these multiple objectives, in particular in a conservation-development context, is often questioned. This study adds to the very limited empirical evidence base and investigates to what extent Vietnam’s move to PES has helped protect forest ecosystems and improve local livelihoods and income inequality. We zoom in on Lam Dong province, where PES was first introduced in Vietnam in 2009. Changes in forest cover are analysed using satellite images over a period of 15 years (2000–2014). Socio-economic impacts are assessed based on rural household interviews with PES participants and non-participants as a control group over a period of 7 years (2008–2014). Our results show that PES contributes significantly to forest cover, the improvement of local livelihoods, and the reduction of income inequality.

Evaluating the Environmental Impact of Debit Card Payments

Purpose: Consumers in the Netherlands made more than 3.2 billion debit card transactions at points-of-sale in 2015, corresponding to over half of all point-of-sale payments in that year. This study provides insights into the environmental impact of debit card transactions based on a life cycle assessment (LCA). In addition, it identifies several areas within the debit card payment chain where the environmental impact can be reduced. Methods: The debit card payment system can be divided into three subsystems: debit cards, payment terminals, and datacentres used for transaction processing. Input data for all elements within each subsystem (manufacturing, transport, energy use, and disposal) were retrieved from interviews and literature study. Seven key companies and authorities within the debit card system such as the Dutch Payments Association, two banks, two datacentres, one payment terminal producer and a recycling company contributed data. The analysis is conducted using SimaPro, the Ecoinvent 3.0 database and the ReCiPe endpoint (H) impact assessment method. Results and discussion: One Dutch debit card transaction in 2015 is estimated to have an absolute environmental impact of 470 µPt. Within the process chain of a debit card transaction, the relative environmental impact of payment terminals is dominant, contributing 75% of the total impact. Terminal materials (37%) and terminal energy use (27%) are the largest contributors to this share, while the remaining impact comprises datacentre (11%) and debit card (15%) subsystems. For datacentres, this impact mainly stems from their energy use. Finally, scenario analyses show that a significant decrease (44%) in the environmental impact of the entire debit card payment system could be achieved by stimulating the use of renewable energy in payment terminals and datacentres, reducing the standby time of payment terminals, and by increasing the lifetimes of debit cards. Conclusions: For the first time, the environmental consequences of electronic card payment systems are evaluated. The total environmental impact of debit card transactions in the Netherlands is relatively modest compared to the impact of cash payments, which are the closest substitute of debit card payments at the point-of-sale. Scenario analysis indicates that the environmental impact can be reduced by 44%.

Death and the Afterlife: A Review Essay

In Death and the Afterlife (2013), Samuel Scheffler has argued that without the expectation that humanity will survive long after we are gone, without the expectation of a ‘collective afterlife’, many of the things that matter to us would cease to do so. Immortality would not be a good thing since our confidence in our values would depend on our status as mortals who lead temporally bounded lives. The purpose of the present review essay is twofold. First, to embed Scheffler’s ‘afterlife conjecture’ in the wider literature. Although the book has been widely praised for pioneering a new field of philosophical inquiry, thought experiments and analyses similar to those by Scheffler have been well known in environmental ethics for more than three decades. Second, to argue that Scheffler’s reasons for rejecting the desirability of immortality are undermined by his afterlife conjecture. Nevertheless, because we are mortals with diminishing capabilities towards the end of our lives, the afterlife conjecture gives us reason to end our lives even if we have the resources to prolong it. Although collective arrangements affecting the elderly have generally been discussed from the point of view of intergenerational solidarity and reciprocity, the values exposed by Schefler’s analysis offer a new perspective.

Electron-energy resolved experiments on multiphoton detachment of negative ions

In many experiments on atoms in strong laser fields, it is the nature of the interaction of the atom with the radiation field which is the subject of investigation, more than the specific structure of the atom which is used. An example of the phenomena that have been discovered in this kind of experiments is the effect of excess-photon ionization (EPI), also called above-threshold ionization (ATI). It is found that electrons can absorb more photons than required to overcome the threshold for ionization and this manifests itself for example in electron-energy spectra consisting of several peaks separated by the photon energy. Since the first observation by Agostini et al1 in 1979, the effect of EPI has been thoroughly investigated2. It was probably initially assumed that in experiments performed at high light intensities the structure of the particular atom was of no importance, however, in later experiments it was found that the structure of the atom leaves its mark on the measurement by means of resonance enhancement of the EPI3.

Fine structure in the 3s3p2 2D perturber of the 3s2nd 2D series in aluminium

The authors investigated the 3s2ns 2S, 3s2nd 2D and the 3s2nf 2F series in aluminium. These high levels were populated by three-photon two-step excitations using the 3s24p 2P3/2 as the intermediate state. They determined the positions of the series members accurately for n values between 28 and 60. The 2S and the 2F series are not perturbed. The quantum defect of the 2S series is confirmed to be 1.728 (2), the quantum defect of the 2F series is 0.041 (2). The perturbation of the 2D series is demonstrated by the variation of the quantum defect over the series, and by the fine structure (FS) of the 2D levels which is measured for n(37. The large positive splitting is shown to be explained by taking into account the fine structure of the 3s3p2 2D perturber. Using simple arguments the percentage of admixture of 3s3p2 2D to the 3s2nd 2D series can be determined while the FS of the perturber is estimated to be 20.5 cm-1.