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Average multiplicity of light nuclei, produced in different interactions at 4.2 AGeV/c is studied as a function of centrality. A change in multiplicity is observed with increase in the mass of projectile. In [.sup.12]CC interactions an unexpected increase in the multiplicity is seen in the most central events. These measurements are compared with the predictions of Cascade and Fritiof models, which fail to account for the experimentally observed effects. In case of 12CC, it is suggested that the inclusion of nuclear coalescence effect can be an explanation for the deviation of experimental measurements from the models' predictions. Key words: collisions, centrality, coalescence, interactions, fragments. Nous etudions la multiplicite moyenne de noyaux legers en fonction de la centralite, dans le produit de differentes interactions a 4.2 AGeV/c. Nous observons un changement de la multiplicite avec l'augmentation de la masse du projectile. Dans les interactions [sup.12]CC, nous notons une augmentation inattendue de la multiplicite dans les evenements les plus centraux. Ces mesures sont comparees aux predictions des modeles de cascade et de Fritiof qui echouent a reproduire cet effet observe. Dans le cas de [sup.12]CC, il est ici suggere que l'inclusion de la coalescence nucleaire puisse expliquer pourquoi les mesures experimentales et les predictions des modeles sont en desaccord. [Traduit par la Redaction] Mots-cles : collisions, centralite, coalescence, interactions, fragments. PACS Nos.: 25.10.+s, 29.85.Fj., Introduction In heavy ion collisions, light nuclei are produced mainly from the disintegration of projectile and target nuclei. However, nuclei are believed to be formed in final state interactions between [...]

We derive a microscopic version of the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for collective rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitudes. The nuclear Schrodinger equation is canonically transformed to collective coordinates, and then linearized using a constrained variational method. The associated constraints are imposed on the wave-function rather than on the particle coordinates. This approach yields three self-consistent, time-reversal invariant, cranking-type Schrodinger equations for the rotation-vibration and intrinsic motions, and a self-consistency equation. For harmonic oscillator mean-field potentials, these equations are solved in closed forms and applied to the ground-state rotational bands in some axially symmetric nuclei. The results are compared with those of other models and related measured data. Key words: multi-particle rotation, multi-particle vibration, intrinsic motion, angular momentum, moments of inertia, canonical transformation, constrained variational method, time-reversal invariance, self-consistency, cranking model, axial symmetry, rotational-band termination or cutoff. Nous derivons une version microscopique du modele hydrodynamique phenomenologique reussi de Bohr-DavydovFaesler-Greiner pour le mouvement de rotation-vibration d'un noyau deforme de symetrie axiale. La derivation n'est pas limitee aux oscillations de faible amplitude. L'equation nucleaire de Schrodinger est canoniquement transformee en coordonnees collectives et ensuite linearisee via une methode variationnelle contrainte. Les contraintes associees sont imposees aux fonctions d'onde plutot qu'aux coordonnees. L'approche donne trois equations de Schrodinger de type cranking, invariantes sous renversement du temps et auto-coherentes. Pour un champ moyen d'oscillateur harmonique, ces equations peuvent etre solutionnees analytiquement et appliquees aux bandes de rotation de noyaux de symetrie axiale. Les resultats sont compares a ceux d'autres modeles et a des valeurs mesurees. [Traduit par la Redaction] Mots-cles: rotation multi-particules, vibration multi-particules, mouvement intrinseque, moment angulaire, moment d'inertie, transformation canonique, methode variationnelle contrainte, invariance sous renversement du temps, auto-coherence, modele de cranking, symetrie axiale, fin de bande de rotation. PACS Nos.: 21.60.Ev, 21.60.FW, 21.60.Jz., 1. Introduction The phenomenological hydrodynamic rotation-vibration model of Bohr-Davydov-Faessler-Greiner (BDFG) [1-5] has been remarkably successful in predicting the properties of low-lying collective rotation and vibration states in deformed nuclei. The [...]

The probability that a nucleus will absorb a neutron--the neutron capture cross-section--is important to many areas of nuclear science, including stellar nucleosynthesis, reactor performance, nuclear medicine and defence applications. Although neutron capture cross-sections have been measured for most stable nuclei, fewer results exist for radioactive isotopes, and statistical-model predictions typically have large uncertainties.sup.1. There are almost no nuclear data for neutron-induced reactions of the radioactive nucleus .sup.88Zr, despite its importance as a diagnostic for nuclear security. Here, by exposing .sup.88Zr to the intense neutron flux of a nuclear reactor, we determine that .sup.88Zr has a thermal neutron capture cross-section of 861,000 [plus or minus] 69,000 barns (1[sigma] uncertainty), which is five orders of magnitude larger than the theoretically predicted value of 10 barns.sup.2. This is the second-largest thermal neutron capture cross-section ever measured and no other cross-section of comparable size has been discovered in the past 70 years. The only other nuclei known to have values greater than 10.sup.5 barns.sup.3-6 are .sup.135Xe (2.6 × 10.sup.6 barns), a fission product that was first discovered as a poison in early reactors.sup.7,8, and .sup.157Gd (2.5 × 10.sup.5 barns), which is used as a detector material.sup.9,10, a burnable reactor poison.sup.11 and a potential medical neutron capture therapy agent.sup.12. In the case of .sup.88Zr neutron capture, both the target and the product (.sup.89Zr) nuclei are radioactive and emit intense [gamma]-rays upon decay, allowing sensitive detection of miniscule quantities of these radionuclides. This result suggests that as additional measurements with radioactive isotopes become feasible with the operation of new nuclear-science facilities, further surprises may be uncovered, with far-reaching implications for our understanding of neutron capture reactions.The thermal neutron capture cross-section of .sup.88Zr is measured to be 861,000 [plus or minus] 69,000 barns, the second-largest neutron capture cross-section ever measured., Author(s): Jennifer A. Shusterman [sup.1] [sup.2] [sup.3] , Nicholas D. Scielzo [sup.1] , Keenan J. Thomas [sup.1] , Eric B. Norman [sup.4] , Suzanne E. Lapi [sup.5] , C. Shaun [...]

Abstract: This paper presents a fractality analysis of the compound multiplicity (pions + target protons) distribution in [sup.12]C-AgBr interactions at 4.5A GeV in terms of moments proposed by Takagi (Phys. [...]

Geometries, energies, and magnetic properties are studied at the ab initio B3LYP/6-31G* level for the three classes of [N]phenylene, which are helical ([N]heliphenes) (N = 14, 19, and 24), zigzag, and linear (N = 14, and 19). Nucleus-independent chemical shift (NICS) values for the heliphenes are found to be small and positive along the helical axis.