40 research outputs found
Irradiation of benzene molecules by ion-induced and light-induced intense fields
Benzene, with its sea of delocalized -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
Correlation dynamics between electrons and ions in the fragmentation of D molecules by short laser pulses
We studied the recollision dynamics between the electrons and D ions
following the tunneling ionization of D molecules in an intense short pulse
laser field. The returning electron collisionally excites the D ion to
excited electronic states from there D can dissociate or be further
ionized by the laser field, resulting in D + D or D + D,
respectively. We modeled the fragmentation dynamics and calculated the
resulting kinetic energy spectrum of D to compare with recent experiments.
Since the recollision time is locked to the tunneling ionization time which
occurs only within fraction of an optical cycle, the peaks in the D kinetic
energy spectra provides a measure of the time when the recollision occurs. This
collision dynamics forms the basis of the molecular clock where the clock can
be read with attosecond precision, as first proposed by Corkum and coworkers.
By analyzing each of the elementary processes leading to the fragmentation
quantitatively, we identified how the molecular clock is to be read from the
measured kinetic energy spectra of D and what laser parameters be used in
order to measure the clock more accurately.Comment: 13 pages with 14 figure
Plant strategies of manipulating predatorprey interactions through allelochemicals: Prospects for application in pest control
Multiple electron capture in slow Ar9+ and 13C5+ on Ne, studied by e--Neq+ coincidences
We have investigated multiple electron capture into autoionizing projectile states during 108 keV Ar9+ and 80 keV C-13(5+) collisions on Ne by measuring autoionization electrons in coincidence with charge state selected target ions. We have determined partial electron energy spectra, corresponding to a well defined number of initially captured electrons. The set-up of the ion and electron spectrometer is described. Trajectory calculations for the determination of detection efficiencies are presented. The partial spectra are discussed in terms of the 'extended classical barrier' model
Coincidences between electrons and target ions to identify capture channels in collisions of multiply charged ions on gas targets
We have investigated multielectron capture processes in collisions of Ar9+ on Ar by measuring the resulting Auger electrons in coincidence with charge-state-analyzed target ions. In this way it was possible to reconstruct partial electron energy spectra, each corresponding to a particular number of initially captured electrons. The spectra are compared with predictions of the extended classical over-barrier model. Strong evidence is found that Auger cascades play an important role for the deexcitation of the highly excited ions, formed by multielectron capture
How to make food system-informed choices to reduce food losses and waste
Policy makers and researchers who try to address food loss and waste increasingly call for a food systems lens to be applied in order to select the best intervention pathways.Putting this into practice, however, is not easy. The Food System Decision Support Toolbox offers guidance to conduct a food system analysis with the participation of a diversity of chain actors, leading to actionable recommendations
The influence of angular momentum on double electron capture by highly charged ions
Double electron capture during collisions of highly charged ions with H-2 or He is studied by measuring and analysing energy spectra of the resulting autoionization electrons and by comparing the experimentally determined population probabilities for the various states with those calculated from a simple classical model. This model is based on the extended classical over-barrier model (ECBM), modified by taking additionally the angular momenta of the exchanged electrons into account. Reasonable agreement between measured and calculated population probabilities for the highly correlated two-electron states is obtained especially for the cases of fully stripped projectiles, although correlation during the exchange process is neglected in the theoretical description. The success of the model implies that highly oriented doubly excited states result from the capture process
Impact of suboptimal temperature on growth, photosynthesis, leaf pigments and carbohydrates of domestic and high-altitude wild Lycopersicon species
The impact of near-optimal (25/20 degrees C) and suboptimal (16/14 degrees C) day/night temperatures on growth, photosynthesis, pigment composition and carbohydrate content was compared between domestic and high-altitude wild Lycopersicon species. When related to the relative shoot growth rate (RSGR) measured at optimal temperature, genotypes of the domestic tomato (L. esculentum (L.) Mill. cv. Abunda and cv. Large Red Cherry (LRC) showed a stronger inhibition of RSGR at suboptimal temperature than the high-altitude wild species L. peruvianum Mill. LA 385 and L. hirsutum Humb. & Bonpl. LA 1777. The initiation rare of new leaves was 2.1-fold faster in all species at 25/20 degrees C than at 16/14 degrees C. In contrast to the other genotypes, the leaf area of suboptimally grown Abunda plants was 28 % smaller than the area of leaves that were fully expanded at optimal temperature. In all species, specific leaf area (SLA) at 16/14 degrees C was 17-26 % lower than at 25/20 degrees C. The percentage of leaf dry matter increased in response to growth ar suboptimal temperature. This increase was higher in L. esculentum genotype Abunda (99 %) than in genotype LRC (38 %), and the wild species L. peruvianum (50 %) and L. hirsutum (38 %), which could be attributed to inter- and intra-specific differences in starch accumulation of 16/14 degrees C-grown leaves. Only in both L. esculentum genotypes, net photosynthetic rate at growth irradiance (A(225)) and at light saturation (A(sat)) was 14 to 30 % lower in leaves grown and measured at suboptimal temperature, compared with leaves grown and measured at optimal temperature (25 degrees C). Chlorophyll (Chl) a fluorescence measurements indicated that the decrease of A225 in leaves of suboptimally grown L. esculentum plants was paralleled by a decrease in the quantum yield of photosystem II electron transport (Phi(PSII)), which could be mainly attributed to a decrease in the photochemical quenching component (q(P)). In all species, the nonphotochemical quenching component (NPQ) was 2 to 4-fold higher at 16/14 degrees C. Growth temperature hardly affected Chi content on a leaf area basis, whereas the content of xanthophyll cycle pigments (violaxanthin + antheraxanthin + zeaxanthin) on a Chi basis was ca. 1.5-fold higher in 16/14 degrees C-grown leaves. The epoxidation state of the xanthophyll cycle pool was only slightly lower in suboptimal leaves due to the moderate growth irradiance