Search results for "binding"
showing 10 items of 3896 documents
Nuclear medium effects in structure functions
2012
We discuss the nuclear-medium effects in the weak structure functions F2(x,Q2) and F3,(x,Q2) in the charged current neutrino and antineutrino induced deep inelastic reactions in some nuclei which are being used in the present or proposed neutrino oscillation experiments. Our study of the medium effects has been done using relativistic nuclear spectral functions which incorporates Fermi motion, binding energy and nucleon correlations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, the results for the differential cross section have been obtained and compared with some of the ava…
Defect recovery in aluminum irradiated with protons at 20 K.
1987
Aluminum single crystals have been irradiated with 7.0-MeV protons at 20 K. The irradiation damage and its recovery are studied with positron-lifetime spectroscopy between 20 and 500 K. Stage-I recovery is observed at 40 K. At 240 K, loss of freely migrating vacancies is observed. Hydrogen in vacancies is found to stabilize the vacancies and prolong stage III to above 280 K, where the hydrogen bound to vacancies is released. Single and multiple occupancy of hydrogen atoms at monovacancies is put forward as the reason for the two recovery stages between 280 and 400 K. A binding energy of 0.53 +- 0.03 eV is found for a hydrogen atom trapped at a monovacancy. The results are in excellent agree…
Penning-trap mass spectrometry and mean-field study of nuclear shape coexistence in the neutron-deficient lead region
2017
We present a study of nuclear shape coexistence in the region of neutron-deficient lead isotopes. The midshell gold isotopes 180,185,188,190Au (Z=79), the two long-lived nuclear states in 197At (Z=85), and the neutron-rich nuclide 219At were produced by the ISOLDE facility at CERN and their masses were determined with the high-precision Penning-trap mass spectrometer ISOLTRAP. The studied gold isotopes address the trend of binding energies in a region of the nuclear chart where the nuclear charge radii show pronounced discontinuities. Significant deviations from the atomic-mass evaluation were found for 188,190Au. The new trend of two-neutron separation energies is smoother, although it doe…
Restoration of theN=82Shell Gap from Direct Mass Measurements ofSn132,134
2008
A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of (134)Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of "shell quenching." In fact, the new shell gap value for the short-lived (132)Sn is larger than that of the doubly magic (48)Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the r process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nu…
First Precision Mass Measurements of Refractory Fission Fragments
2005
Atomic masses of 95-100Sr, 98-105Zr, and [corrected] 102-110Mo and have been measured with a precision of 10 keV employing a Penning trap setup at the IGISOL facility. Masses of 104,105Zr and 109,110Mo are measured for the first time. Our improved results indicate significant deviations from the previously published values deduced from beta end point measurements. The most neutron-rich studied isotopes are found to be significantly less bound (1 MeV) compared to the 2003 atomic mass evaluation. A strong correlation between nuclear deformation and the binding energy is observed in the two-neutron separation energy in all studied isotope chains.
Translationally invariant coupled cluster method in coordinate space for nuclei
2002
We study a formulation of the translationally invariant coupled cluster method in coordinate space for finite nuclei. The new formulation remedies convergence problems that plagued previous calculations in configuration space. The method is applied to light nuclei using semi-realistic central interactions.
Energy- and k -resolved mapping of the magnetic circular dichroism in threshold photoemission from Co films on Pt(111)
2017
The magnetic circular dichroism in threshold photoemission (TPMCD) for perpendicularly magnetized fcc Co films on Pt(111) has been revisited. A complete mapping of the spectral function $I({E}_{B},{k}_{x},{k}_{y})$ (binding energy ${E}_{B}$, momentum parallel to surface ${k}_{x}$, ${k}_{y}$) and the corresponding TPMCD asymmetry distribution ${A}_{\mathrm{MCD}}({E}_{B},{k}_{x},{k}_{y})$ has been performed for one-photon and two-photon photoemission using time-of-flight momentum microscopy. The experimental results allow distinguishing direct from indirect transitions. The measurements reveal clear band features of direct transitions from bulk bands that show a nontrivial asymmetry pattern. …
Force-clamp spectroscopy of reversible bond breakage.
2008
We consider reversible breaking of adhesion bonds or folding of proteins under the influence of a constant external force. We discuss the stochastic properties of the unbinding/rebinding events and analyze their mean number and their variance in the framework of simple two-state models. In the calculations, we exploit the analogy to single molecule fluorescence and particularly between unbinding/rebinding and photon emission events. Environmental fluctuation models are used to describe deviations from Markovian behavior. The second moment of the event-number distribution is found to be very sensitive to possible exchange processes and can thus be used to identify temporal fluctuations of th…
Direct Mapping of Nuclear Shell Effects in the Heaviest Elements
2014
Quantum-mechanical shell effects are expected to strongly enhance nuclear binding on an "island of stability" of superheavy elements. The predicted center at proton number $Z=114,120$, or $126$ and neutron number $N=184$ has been substantiated by the recent synthesis of new elements up to $Z=118$. However the location of the center and the extension of the island of stability remain vague. High-precision mass spectrometry allows the direct measurement of nuclear binding energies and thus the determination of the strength of shell effects. Here, we present such measurements for nobelium and lawrencium isotopes, which also pin down the deformed shell gap at $N=152$.
Gamma/neutron competition above the neutron separation energy in delayed neutron emitters
2014
To study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyvaskyla in Finland) using Total Absorption -ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn. © Owned by the authors, published by EDP Sciences, 2014.