36 research outputs found
Overlapping resonances in nuclei coupling to the atomic shells
The resonant process of nuclear excitation by electron transition (NEET) in
highly charged ions is investigated. In NEET, a bound electronic decay
transition occurs with the simultaneous excitation of the nucleus, provided
that the energies of the atomic and nuclear transition match. By varying the
atomic charge state, the atomic transition energy can be tuned to a better
match of the nuclear transition energy. We propose a new way to create the
atomic hole in highly charged ions by dielectronic capture of a free electron.
In order to derive the cross section for the three-step process composed by
dielectronic capture, NEET, and the subsequent nuclear decay, a Feshbach
projection operator formalism is developed. With the help of this formalism,
the resonances in nuclei coupling to the atomic shell and the possible
interference between several direct and resonant electronic and nuclear
processes such as radiative recombination, dielectronic recombination and
nuclear excitation by electron capture are described.Comment: 15 pages, 5 figures, updated to the published versio
Photon angular distribution and nuclear-state alignment in nuclear excitation by electron capture
The alignment of nuclear states resonantly formed in nuclear excitation by
electron capture (NEEC) is studied by means of a density matrix technique. The
vibrational excitations of the nucleus are described by a collective model and
the electrons are treated in a relativistic framework. Formulas for the angular
distribution of photons emitted in the nuclear relaxation are derived. We
present numerical results for alignment parameters and photon angular
distributions for a number of heavy elements in the case of E2 nuclear
transitions. Our results are intended to help future experimental attempts to
discern NEEC from radiative recombination, which is the dominant competing
process
The mineralogical composition of calcium and calcium-magnesium carbonate pedofeatures of calcareous soils in the European prairie ecodivision in Hungary
Abstract
There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data.
The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination.
Regarding carbonate minerals only aragonite, calcite (+ magnesian calcite) and dolomite (+proto-dolomite) were identified in carbonate grains, skeletons and pedofeatures.
The values relating, respectively, to stable isotope compositions (C13, O18) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation.
Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils.
Differences were found in substance-regimes types of soils rather than in soil types
Portraits, painters, patrons. To the 16–17<sup>th</sup> century history of portraiture in areas of the Hungarian kingdom
The mineralogical composition of calcium and calcium-magnesium carbonate pedofeatures of calcareous soils in the European prairie ecodivision in Hungary
Photosynthetic characteristics of the benthic diatom species Nitzschia frustulum (Kützing) Grunow isolated from a soda pan along temperature-, sulfate- and chloride gradients
X-ray quantum optics
Quantum optics with X-rays has long been a somewhat exotic activity, but it is now rapidly becoming relevant as precision x-ray optics and novel X-ray light sources, and high-intensity lasers are becoming available. This article gives an overview of the current state of the field and an outlook to future prospects