85 research outputs found
Does The 3N-Force Have A Hard Core?
The meson-nucleon dynamics that generates the hard core of the RuhrPot
two-nucleon interaction is shown to vanish in the irreducible 3N force. This
result indicates a small 3N force dominated by conventional light
meson-exchange dynamics and holds for an arbitrary meson-theoretic Lagrangian.
The resulting RuhrPot 3N force is defined in the appendix. A completely
different result is expected when the Tamm-Dancoff/Bloch-Horowitz procedure is
used to define the NN and 3N potentials. In that approach, (e.g. full Bonn
potential) both the NN {\it and} 3N potentials contain non-vanishing
contributions from the coherent sum of meson-recoil dynamics and the
possibility of a large hard core requiring explicit calculation cannot be ruled
out.Comment: 16 pages REVTeX + 3 ps fig
Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films
The ultrafast photoinjection and subsequent relaxation steps of the indoline dye D149 were investigated in detail for a mesoporous electrodeposited ZnO thin film and compared with experiments on sintered TiO2 and ZrO2 thin films, all in contact with air, using pump-supercontinuum probe (PSCP) transient absorption spectroscopy in the range 370-770 nm. D149 efficiently injects electrons into the ZnO surface with time constants from â€70 fs (time-resolution-limited) up to 250 fs, without the presence of slower components. Subsequent spectral dynamics with a time constant of 20 ps and no accompanying change in the oscillator strength are assigned to a transient Stark shift of the electronic absorption spectrum of D149 molecules in the electronic ground state due to the local electric field exerted by the D149 âą+ radical cations and conduction band electrons in ZnO. This interpretation is consistent with the shape of the relaxed PSCP spectrum at long times, which resembles the first derivative of the inverted steady-state absorption spectrum of D149. In addition, steady-state difference absorption spectra of D149âą+ in solution from spectroelectrochemistry display a bleach band with distinctly different position, because no first-order Stark effect is present in that case. Interference features in the PSCP spectra probably arise from a change of the refractive index of ZnO caused by the injected electrons. The 20 ps component in the PSCP spectra is likely a manifestation of the transition from an initially formed bound D149 âą+-electron complex to isolated D149âą+ and mobile electrons in the ZnO conduction band (which changes the external electric field experienced by D149) and possibly also reorientational motion of D149 molecules in response to the electric field. We identify additional spectral dynamics on a similar timescale, arising from vibrational relaxation of D149âą+ by interactions with ZnO. TiO2 exhibits similar dynamics to ZnO. In the case of ZrO2, electron injection accesses trap states, which exhibit a substantial probability for charge recombination. No Stark shift is observed in this case. In addition, the spectroelectrochemical experiments for D149âą+ in dichloromethane and acetonitrile, which cover the spectral range up to 2000 nm, provide for the first time access to its complete D0 â D1 absorption band, with the peak located at 1250 and 1055 nm, respectively. Good agreement is obtained with results from DFT/TDDFT calculations of the D149 âą+ spectrum employing the MPW1K functional. © 2012 the Owner Societies
Tailoring surface topographies on solids with Mid-IR femtosecond laser pulses
Irradiation of solids with ultrashort pulses using laser sources in the
mid-infrared (mid-IR) spectral region is a yet predominantly unexplored field
that opens broad possibilities for efficient and precise surface texturing for
a wide range of applications. In the present work, we investigate both
experimentally and theoretically the impact of laser sources on the generation
of surface modification related effects and on the subsequent surface
patterning of metallic and semiconducting materials. Through a parametric study
we correlate the mid-IR pulsed laser parameters with the onset of material
damage and the formation of a variety of periodic surface structures at a laser
wavelength of {\lambda}L=3200 nm and a pulse duration of {\tau}p=45 fs. Results
for nickel and silicon indicate that the produced topographies comprise both
high and low spatial frequency induced periodic structures, similar to those
observed at lower wavelengths, while groove formation is absent. The
investigation of the damage thresholds suggests the incorporation of nonlinear
effects generated from three-photon-assisted excitation (for silicon) and the
consideration of the role of the non-thermal excited electron population (for
nickel) at very short pulse durations. The results demonstrate the potential of
surface structuring with mid-IR pulses, which can constitute a systematic novel
engineering approach with strong fields at long-wavelength spectral regions
that can be used for advanced industrial laser applications
Single-Shot Electron Imaging of Dopant-Induced Nanoplasmas
We present single-shot electron velocity-map images of nanoplasmas generated from doped helium nanodroplets and neon clusters by intense near-infrared and mid-infrared laser pulses. We report a large variety of signal types, most crucially depending on the cluster size. The common feature is a two-component distribution for each single-cluster event: a bright inner part with nearly circular shape corresponding to electron energies up to a few eV, surrounded by an extended background of more energetic electrons. The total counts and energy of the electrons in the inner part are strongly correlated and follow a simple power-law dependence. Deviations from the circular shape of the inner electrons observed for neon clusters and large helium nanodroplets indicate non-spherical shapes of the neutral clusters. The dependence of the measured electron energies on the extraction voltage of the spectrometer indicates that the evolution of the nanoplasma is significantly affected by the presence of an external electric field. This conjecture is confirmed by molecular dynamics simulations, which reproduce the salient features of the experimental electron spectra.The authors are grateful for financial support from the Deutsche Forschungsgemeinschaft (DFG) within the
project MU 2347/12-1 and STI 125/22-2 in the frame of the Priority Programme 1840 âQuantum Dynamics
in Tailored Intense Fieldsâ, from the Carlsberg Foundation and the SPARC Programme, MHRD, India. The
ELI-ALPS Project (GINOP-2.3.6-15-2015-00001) is supported by the European Union and co-financed by
the European Regional Development Fund. AH is grateful for financial support from the Basque
Government (Project Reference No. IT1254-19) and from the Spanish Ministerio de Economia y
Competividad (Reference No. CTQ2015-67660-P). Computational and manpower support provided by
IZO-SGI SG Iker of UPV/EHU and European funding (EDRF and ESF) is gratefully acknowledged
UV continuum emission and diagnostics of hydrogen-containing non-equilibrium plasmas
For the first time the emission of the radiative dissociation continuum of
the hydrogen molecule ( electronic
transition) is proposed to be used as a source of information for the
spectroscopic diagnostics of non-equilibrium plasmas. The detailed analysis of
excitation-deactivation kinetics, rate constants of various collisional and
radiative transitions and fitting procedures made it possible to develop two
new methods of diagnostics of: (1) the ground state
vibrational temperature from the relative intensity
distribution, and (2) the rate of electron impact dissociation
(d[\mbox{H_{2}}]/dt)_{\text{diss}} from the absolute intensity of the
continuum. A known method of determination of from relative
intensities of Fulcher- bands was seriously corrected and simplified
due to the revision of transition probabilities and cross sections of
electron impact excitation. General considerations are illustrated
with examples of experiments in pure hydrogen capillary-arc and H+Ar
microwave discharges.Comment: REVTeX, 25 pages + 12 figures + 9 tables. Phys. Rev. E, eprint
replaced because of resubmission to journal after referee's 2nd repor
Consistent off-shell vertex and nucleon self-energy
We present a consistent calculation of half-off-shell form factors in the
pion-nucleon vertex and the nucleon self-energy. Numerical results are
presented. Near the on-shell point the pion-nucleon vertex is dominated by the
pseudovector coupling, while at large nucleon invariant masses we find a
sizable pseudoscalar admixture.Comment: 23 pages, 7 figures, REVTeX, submitted to Phys. Rev. C, replaced with
corrected versio
Imprint of DES superstructures on the cosmic microwave background
Small temperature anisotropies in the cosmic microwave background (CMB) can be sourced by density perturbations via the late-time integrated Sachs-Wolfe (ISW) effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey (DES) in a different footprint, and using a different superstructure finding strategy. We identified 52 large voids and 102 superclusters at redshifts 0.2 < z < 0.65. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with DeltaTf â -5.0 ± 3.7 muK and a hot imprint of superclusters DeltaTf â 5.1 ± 3.2 muK; this is Ë1.2sigma higher than the expected |DeltaTf| â 0.6 muK imprint of such superstructures in Lambda cold dark matter (LambdaCDM). If we instead use an a posteriori selected filter size (R/Rv = 0.6), we can find a temperature decrement as large as DeltaTf â -9.8 ± 4.7 muK for voids, which is Ë2sigma above LambdaCDM expectations and is comparable to previous measurements made using Sloan Digital Sky Survey superstructure data
A CMB Gibbs sampler for localized secondary anisotropies
As well as primary fluctuations, CMB temperature maps contain a wealth of additional information in the form of secondary anisotropies. Secondary effects that can be identified with individual objects, such as the thermal and kinetic Sunyaev-Zel'dovich (SZ) effects due to galaxy clusters, are difficult to unambiguously disentangle from foreground contamination and the primary CMB however. We develop a Bayesian formalism for rigorously characterising anisotropies that are localised on the sky, taking the TSZ and KSZ effects as an example. Using a Gibbs sampling scheme, we are able to efficiently sample from the joint posterior distribution for a multi-component model of the sky with many thousands of correlated physical parameters. The posterior can then be exactly marginalised to estimate properties of the secondary anisotropies, fully taking into account degeneracies with the other signals in the CMB map. We show that this method is computationally tractable using a simple implementation based on the existing Commander component separation code, and also discuss how other types of secondary anisotropy can be accommodated within our framework
Individual development of preschool children - prevalences and determinants of delays in Germany: a cross-sectional study in Southern Bavaria
The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2431/12/188 Extent: 9p.Background: Even minor abnormalities of early child development may have dramatic long term consequences. Accurate prevalence rates for a range of developmental impairments have been difficult to establish. Since related studies have used different methodological approaches, direct comparisons of the prevalence of developmental delays are difficult. The understanding of the key factors affecting child development, especially in preschool aged children remains limited. We used data from school entry examinations in Bavaria to measure the prevalence of developmental impairments in pre-school children beginning primary school in 1997â2009. Methods: The developmental impairments of all school beginners in the district of Dingolfing- Landau, Bavaria were assessed using modified âBavarian School Entry Modelâ examination from 1997 to 2009 (N=13,182). The children were assessed for motor, cognitive, language and psychosocial impairments using a standardised medical protocol. Prevalence rates of impairments in twelve domains of development were estimated. Using uni- and multivariable logistic regression models, association between selected factors and development delays were assessed. Results: The highest prevalence existed for impairments of pronunciation (13.8%) followed by fine motor impairments (12.2%), and impairments of memory and concentration (11.3%) and the lowest for impairments of rhythm of speech (3.1%). Younger children displayed more developmental delays. Male gender was strongly associated with all developmental impairments (highest risk for fine motor impairments = OR 3.22, 95% confidence interval 2.86-3.63). Preschool children with siblings (vs. children without any siblings) were at higher risk of having impairments in pronunciation (OR 1.31, 1.14-1.50). The influence of the non-German nationality was strong, with a maximum risk increase for the subareas of grammar and psychosocial development. Although children with non-German nationality had a reduced risk of disorders for the rhythm of speech and pronunciation, in all other 10 subareas their risk was increased. Conclusions: In preschool children, most common were delays of pronunciation, memory and concentration. Age effects suggest that delays can spontaneously resolve, but providing support at school entry might be helpful. Boys and migrant children appear at high risk of developmental problems, which may warrant tailored intervention strategies.Heribert L Stich, Bernhard Th Baune, Riccardo N Caniato, Rafael T Mikolajczyk and Alexander KrĂ€me
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