Dissociation spectrum of H2+_2^+ from a short, intense infrared laser pulse: vibration structure and focal volume effects

The dissociation spectrum of the hydrogen molecular ion by short intense pulses of infrared light is calculated. The time-dependent Schr\"odinger equation is discretized and integrated in position and momentum space. For few-cycle pulses one can resolve vibrational structure that commonly arises in the experimental preparation of the molecular ion from the neutral molecule. We calculate the corresponding energy spectrum and analyze the dependence on the pulse time-delay, pulse length, and intensity of the laser for $\lambda \sim 790$nm. We conclude that the proton spectrum is a both a sensitive probe of the vibrational dynamics and the laser pulse. Finally we compare our results with recent measurements of the proton spectrum for 55 fs pulses using a Ti:Sapphire laser ($\lambda \sim 790$nm). Integrating over the laser focal volume, for the intensity $I \sim 3 \times 10^{15}$W cm$^{-2}$, we find our results are in excellent agreement with these experiments.Comment: 17 pages, 8 figures, preprin

Adoption of terraces in the Peruvian Andes

Soil erosion is a serious constraint for agriculture and rural development in developing countries. Many efforts are made to promote soil and water conservation (SWC) among farm households. However, adoption of SWC practices is often disappointing. This thesis analyses the benefits of terraces and the adoption behaviour of farm households in the Peruvian Andes. The main beneficial effect of terraces is the increased water availability in the soils. However, terraces will only result in increased production if it is combined with intensified crop management or with crops of high market value. Whether terraces are financially attractive for farmers depends mainly on their personal opportunity cost of labour. Incentives though only slightly increase the profitability of terraces. The decision to participate in a SWC-oriented programme plays a key role in the adoption process. Programmes with a top-down approach have a strong influence on the adoption decision. Participants of these programmes installed SWC practices on the rainfed and degraded fields with steep slopes that are used for extensive agriculture or pasture. Participants of a participatory programme have more individual control on the adoption decision, and they installed terraces on the less degraded fields in order to intensify agricultural production. Production functions revealed that terraces do not result in a significant increase of agricultural output at household level, but labour productivity did increase. Terraces have the potential to increase agricultural production and factor productivity, but whether this is of interest of a farm household, depends on the existing markets. Therefore, programmes have to take into account the scarcity of production factors and the opportunities at local markets. As conditions differ per region, SWC interventions should be decentralised

Dissociation and ionization of small molecules steered by external noise

We show that ionization and dissociation can be influenced separately in a molecule with appropriate external noise. Specifically we investigate the hydrogen molecular ion under a stochastic force quantum mechanically beyond the Born-Oppenheimer approximation. We find that up to 30% of dissociation without ionization can be achieved by suitably tuning the forcing parameters.Comment: 13 pages, 6 figure

Semiclassical ionization dynamics of the hydrogen molecular ion in an electric field of arbitrary orientation

Quasi-static models of barrier suppression have played a major role in our understanding of the ionization of atoms and molecules in strong laser fields. Despite their success, in the case of diatomic molecules these studies have so far been restricted to fields aligned with the molecular axis. In this paper we investigate the locations and heights of the potential barriers in the hydrogen molecular ion in an electric field of arbitrary orientation. We find that the barriers undergo bifurcations as the external field strength and direction are varied. This phenomenon represents an unexpected level of intricacy even on this most elementary level of the dynamics. We describe the dynamics of tunnelling ionization through the barriers semiclassically and use our results to shed new light on the success of a recent theory of molecular tunnelling ionization as well as earlier theories that restrict the electric field to be aligned with the molecular axis

The propensity of molecules to spatially align in intense light fields

The propensity of molecules to spatially align along the polarization vector of intense, pulsed light fields is related to readily-accessible parameters (molecular polarizabilities, moment of inertia, peak intensity of the light and its pulse duration). Predictions can now be made of which molecules can be spatially aligned, and under what circumstances, upon irradiation by intense light. Accounting for both enhanced ionization and hyperpolarizability, it is shown that {\it all} molecules can be aligned, even those with the smallest static polarizability, when subjected to the shortest available laser pulses (of sufficient intensity).Comment: 8 pages, 4 figures, to be submitted to PR

Landbouwverkenning provincie Fryslân tot 2020

In deze toekomstverkenning voor de Friese landbouw, in opdracht van de provincie Fryslân, wordt naast inzicht in de huidige kracht van de agrarische sector, vooral een beeld gegeven van de mogelijke kansen en bedreigingen die relevante beleids- en marktontwikkelingen met zich mee zullen brengen. Op basis van de SWOT wordt een verwacht beeld geschetst van hoe de Friese landbouw zich richting 2020 ontwikkelt. De toekomstverkenning richt zich vooral op de sectoren melkveehouderij, akkerbouw, glastuinbouw en biologische landbouw. De verkenning levert bouwstenen op voor een verdere invulling van het toekomstig provinciaal beleid voor de agrarische secto

Improving interprofessional coordination in Dutch midwifery and obstetrics: A qualitative study

Background: Coordination between the autonomous professional groups in midwifery and obstetrics is a key debate in the Netherlands. At the same time, it remains unclear what the current coordination challenges are. Methods: To examine coordination challenges that might present a barrie

Nuclear classical dynamics of H2_2 in intense laser field

In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization respectively. In the second part of the paper, the time dependent Schr\"{o}dinger and Newton equations are solved simultaneously for the electrons and the nuclei of H$_2$ respectively. The electrons and nuclei dynamics are separated on the base of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390 nm, 532 nm and 780 nm) and intensities ($5\times10^{14}$ $Wcm^{-2}$ and $5\times10^{15}$ $Wcm^{-2}$) of the ultrashort intense laser pulses with a sinus second order envelope function are used. The behaviour of the time dependent classical nuclear dynamics in the absence and present of the laser field are investigated and compared. In the absence of the laser field, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.Comment: 16 pages, 7 figure

Irradiation of benzene molecules by ion-induced and light-induced intense fields

Benzene, with its sea of delocalized $\pi$-electrons in the valence orbitals, is identified as an example of a class of molecules that enable establishment of the correspondence between intense ion-induced and laser-light-induced fields in experiments that probe ionization dynamics in temporal regimes spanning the attosecond and picosecond ranges.Comment: 4 ps figure