Multimodal analysis of prompt neutron spectra for 237Np(n,f)

An attempt was made to analyzed the systematic variation of the prompt neutron spectra of ²³⁷Np(n,f) on the basis of the multimodal analysis of mass and kinetic energy distributions. The spectra of neutrons emitted from fragments of each mode (standard I, II, III, superlong) were calculated independently and the total spectra were synthesized. It was found that the partial spectrum for standard I mode is the softest, getting harder in ascending order for standard II, standard III and superlong modes. The calculated total spectra well represented the experimental data and were found to be more sensitive to the variation of the incident energy than the conventional treatment of the Madland-Nix model.     

Studies on the level structure of154Gd via the β-decay of154Eu nucleus

The excited states of¹⁵⁴Gd populated by theβ-decay of¹⁵⁴Eu (T _1/2=8.5y) have been studied. With a HPGe-NaI (T1) Compton suppression spectrometer and a HPGe-NaI(T1) coincidence circuitυ-ray singles spectra, coincidence spectra and theγ-γ directional correlational functions have been obtained. The deduced mixing ratios of multipolarities are presented. The energy levels and the relativeB(E2) values of the variousγ-transitions in¹⁵⁴Gd nucleus have been calculated both in the IBA model and it's extended version with boson surface delta interaction (BSDI).     

Fine structure in the He(I)/He(II) photoelectron spectra of the metal valence (d) shells of the group IIB dihalides

The He(I) and He(II) photoelectron spectra of the group IIB dihalides (except the difluorides) are reported. Emphasis is laid on the metal valence d-shell ionizations. These are discussed in terms of He(I)/He(II) relative intensity changes a ligand-field model. It appears that the observed d-shell structure is the result of a balance between simple field-effects and covalency.     

Interference effects in alignment and orientation processes of atoms excited by polarized radiation

The dynamics of the processes of alignment and orientation of atoms subjected to the action of polarized radiation has been studied theoretically in the energy range of excitation of autoionization resonances. The alignment parameters A ₂₀ for the 4p ⁴5p states of Kr II populated through the excitation and autoionization decay of Kr I 3d ⁹ np resonances depend on energy due to the interference between different resonance channels and the channel of direct photoionization. It is predicted that the orientation parameter O ₁₀ of some Kr II 4p ⁴5p states and the parameter of the angular distribution of photoelectrons β_e1 strongly depend on energy. The absolute photoionization cross sections are calculated for the population of the Kr II 4p ⁴5p states in the case where the energy of excitation photons corresponds to the first four 3d ⁹ np resonances. A good agreement between the calculated and measured photoionization cross sections proves that it is important to take into account the interference between different resonance channels in order to appreciate the dynamics of the Auger decay of Kr I 3d ⁹ np resonances.     

Three-body final state breakup in the27Al(14N,X) reaction at 116 MeV bombarding energy

The energy spectra and angular distributions of products in the reaction²⁷Al(¹⁴N,X) have been measured at 116 MeV bombarding energy. It is shown that the energy spectra of the products lighter than the projectile, are well described by a three-body breakup calculation. The experimental total breakup cross-section estimated in the present work, together with Glas-Mosel calculation of the fusion cross-section, are in a reasonable agreement with the optical model total reaction cross-section.     

Microscopic interacting boson model calculations for even-even <Superscript>128–138</Superscript>Ce nuclei

In this study, we determined the most appropriate Hamiltonian that is needed for the present calculations of energy levels and B(E2) values of ^128–138Ce nuclei which have a mass around A≅130 using the interacting boson model (IBM). Using the best-fitted values of parameters in the Hamiltonian of the IBM-2, we have calculated energy levels and B(E2) values for a number of transitions in ^{128,130,132,134,136,138}Ce. The results were compared with the previous experimental and theoretical (PTSM model) data and it was observed that they are in good agreement. Also some predictions of this model have better accuracy than those of PTSM model. It has turned out that the interacting boson approximation (IBA) is fairly reliable for calculating spectra in the entire set of ^{128,130,132,134,136,138}Ce isotopes and the quality of the fits presented in this paper is acceptable.      

Shape transitions and shape coexistence in the Ru and Hg chains

The General Collective Model (GCM) is revised and applied to the chain of^182–196Hg- and^96–108Ru-isotopes. Calculated energy spectra, absolute B(E2) values and Quadrupole moments are presented and compared to experiment. For many of these nuclei a coexistence of spherical and triaxial shapes was found. Additionally we investigated the shape transition within the Ru-chain from prolate (⁹⁶Ru) over spherical (⁹⁸Ru) to triaxial (A ≧100). The results are compared to microscopic and IBA calculations.     

The 64Ni(6Li,d)68Zn reaction

The ⁶⁴Ni(⁶Li, d)⁶⁸Zn reaction has been studied at 28 MeV bombarding energy. For several low-lying states in ⁶⁸Zn, S-values extracted via DWBA analysis are compared with shell model and collective model (IBA) predictions.     

Thermoluminescence and electron spin resonance after room-temperature X-ray irradiation of NaCl:Mn2+

A parallel investigation of thermoluminescence (TL) and electron spin resonance (ESR) spectra on room-temperature (RT) X-irradiated NaCl:Mn²⁺ has been performed. The TL spectra in the range 20–300°C consist of five glow peaks, numbered from I to V. Temperatures at maximum height are 41°, 68°, 118°, 152° and 216°C, respectively. Peaks I, II and IV obey first-order kinetics, whereas peaks III and V fit second-order behavior. The wavelength spectrum for all glow peaks consists of two bands centered at 595 and 400 nm. The 595 nm emission is attributed to hole capture by Mn⁺ and subsequent deexcitation of Mn²⁺. The 400 nm emission is produced as a consequence of hole-F center recombination.The correlation of TL glow peaks to various defects has been investigated. Peak II is clearly related to manganese-vacancy dipoles and peak I can be roughly associated to free cation vacancies. Peak IV appears to relate to large Mn-aggregates, whereas peak V is intrinsic and not related to impurities.On the other hand, ESR data indicate that each glow peak in the 595 nm emission is associated to the annihilation of a given Mn-center; Peak I to Mn⁰C, peak II to Mn⁰C and Mn⁺, peak III to Mn⁺ and peaks IV and V to Mn⁰-D.     

A Mössbauer study of octahedral site symmetries in systems Co x Mn3−x−y Fe y O4 and Ni x Mn3−x−y Fe y O4

A Mössbauer study of cation distribution in systems Co _x Mn_3?x?y Fe _y O₄ and Ni _x Mn_3?x?y Fe _y O₄ has been made. It has been found that in both systems all specimens withy<0.6 value exhibit quadrupole doublets corresponding to site symmetries Fe³⁺(I) and Fe³⁺(II) of octahedral site. As more and more cobalt or nickel is introduced into the matrix the intensity of the inner quadrupole doublet increases while on introducing iron that of the outer quadrupole doublet increases. After a certain concentration of iron the inner doublet starts becoming more intense. It is suggested that this arises possibly from the substitution of cations in the second co-ordination sphere of Fe³⁺(I) and Fe³⁺(II) sites. Fory>0.6 the Mössbauer spectra show relaxation effects.     

Magnetic-field-induced orientation of photosynthetic reaction centers as revealed by time-resolved W-band EPR of spin-correlated radical paris: Development of a molecular model

Spin-correlated radical pairs are the short-lived intermediates of the primary energy conversion steps of photosynthesis. In this paper, we develop a comprehensive model for the spin-polarized electron paramagnetic resonance (EPR) spectra of these systems. Particular emphasis is given to a proper treatment of the alignment of the photosynthetic bacteria by the field of the EPR spectormeter. The model is employed to analyze time-resolved W-band (94 GHz) EPR spectra of the secondary radical pair P ₇₀₀ ⁺ A ₁ ^? in photosystem I formed by photoexcitation of the deuterated and¹⁵N-substituted cyanobacteriumSynechococcus lividus. Computer simulations of the angular-dependent EPR spectra of P^700/+A_1/? provide values for the order parameter of the cyanobacterial cells and for the orientation of the membrane normal in a molecular reference system. The order parameter from EPR compares favorably with corresponding data from electron microscopy obtained for theS. lividus cells under similar experimental conditions. It is shown that high-field EPR of a magnetically aligned sample in combination with the study of quantum beat oscillations represents a powerful structural tool for the short-lived radical pair intermediates of photosynthesis.     

Formic acid anhydride: Matrix infrared spectra of five isotopic species,vibrational analysis,empirical and ab initio harmonic force field and thermodynamic functions

Argon matrix infrared spectra of formic acid anhydride (CHOOCHO, CDOOCHO, CDOOCDO, and CH¹⁸O¹⁸OCH¹⁸O) are presented. Assignments and normal coordinate analysis yield valence force constants (VFF I) reflecting a significant dependence on the conformation of the formyl groups. A similar dependence is borne out by force constants obtained from an ab initio SCF treatment. The quantum chemical force constants qualitatively confirm Badger's rule. It is shown that a second valence force field (VFF II) may be found which is in qualitative agreement with the quantum chemical force constants and also reproduces the observed frequencies just as well as VFF I. The stretching force constants appear to be enhanced for bonds which are trans to another bond.     

Analysis of charged-particle production in nucleus-nucleus interactions near and beyond the kinematical limit for free NN collisions within the FRITIOF model

The production of charged particles (π ^± mesons and protons) in nucleus-nucleus interactions at energies in the range 3.3–3.7 GeV/nucleon is considered. It is shown that the FRITIOF model adapted to moderately high energies reproduces satisfactorily the energy spectra of mesons emitted into the backward hemisphere in the laboratory frame, as well as their dependence on the masses of colliding nuclei. The FRITIOF model supplemented with the Reggeon model of nuclear breakup allows one to describe the soft part of the spectra of backward-emitted protons. Other approaches are required for describing the hard part of the spectra.     

Calculations of the energy spectra of Zn,Ga, and Ge isotopes by the shell model

The effective Hamiltonian which was determined empirically by Koops and Glaudemans is tested in shell model calculations for the^65–68Zn,^67–69Ga, and^68–70Ge nuclei in the full (1p _3/2,0f _5/2,1p _1/2) ⁿ space. The resulting energy spectra are compared with the experimental spectra and results of previous calculations. The overall agreement with experiment is as satisfactory for these nuclei as for the Ni and Cu isotopes, by which the Hamiltonian was determined. It is noticed that the spectra of⁶⁷Zn and^67,69Ga calculated in this work are similar to those provided by the Alaga model.     

Auger transitions in Li-like and Be-like ions

Measurements of the Auger decay of beam-foil excited Be II and Be I levels are reported along with a proposed assignment of the experimental spectra. The Li I, Be II and Be III (1s2s²)²S → (1s²2s)²S Auger transitions as presented in this letter represents the first observation of such states in positive ions with Z?5.     

Theoretical energy distributions of atoms sputtered from elastic collision spikes by monomer and dimer ion bombardment

The energy spectra of atoms sputtered from metal targets by bombardment with heavy monomer and dimer ions have been investigated on the basis of a standard model for elastic collision spikes. In particular we calculated the energy distributions for a Au sample bombarded by 4 keV I⁺ and 8 keV I ₂ ⁺ ions. The results were compared with the recent time of flight measurements performed by de Vries and coworkers. It was shown that the model described accurately most of the experimental observations: the count rates and the relative cascade to spike ratios for both I⁺ and I ₂ ⁺ projectiles, and the energy spectrum for dimer sputtering. The spectrum for monomer bombardment, however, was shifted towards lower energies in comparison to the experimental one. The possible source of this discrepancy is discussed.This work was supported by the Central Research Program CPBP 01.09     

Nuclear magnetic resonance and transferred hyperfine interaction study of the crystallographically inequivalent Cs(I) and Cs(II) in a Cs2CuCl4 single crystal

¹³³Cs (I=7/2) nuclear magnetic resonance in a Cs₂CuCl₄ single crystal grown by using the slow evaporation method was measured in its three mutually perpendicular crystal planes. The ¹³³Cs resonances of two different groups with two crystallographically inequivalent cesium nuclei, Cs(I) and Cs(II), in the unit cell were recorded. The transferred hyperfine fields for Cs(I) and Cs(II) calculated from the paramagnetic shift and the molecular susceptibility measurements could be expressed by the linear equation H_hf=AT+B. The angular dependence of the ¹³³Cs nuclear magnetic resonance spectra showed that the Cs(I) and the Cs(II) nuclei had different values for the quadrupole coupling constant. The electric field gradient tensors of Cs(I) and Cs(II) were symmetric, and the orientations of their principal axes did not coincide. The Cs(I) ion surrounded by 11 chlorine ions had a small quadrupole parameter, a smaller charge distribution, and a small value for the transferred hyperfine field. However, the Cs(II) ion surrounded by nine chlorine ions had a larger quadrupole parameter, a larger charge distribution, and a larger value for the transferred hyperfine field.