The ground stateM1 strength in40Ca

The M1 gamma decay strengths of the ground state transitions of the 1⁺,T=1 states of⁴⁰Ca at 9.86 MeV and 10.32 MeV have been measured using the reaction³⁹K(p,γ)⁴⁰Ca. The measured ground state gamma decay widths of these levels are 1.06±0.15 eV and 5.8±0.8 eV respectively. These relatively large M1 strengths can be explained by a shell model calculation incorporating excited core configurations.     

Distribution of dipole and spin-dipole strength in nuclei

The schematic model of Goswami and Pal is applied to heavy nuclei and the dipole strength is shown to reside in just four non-degenerate levels. The collection of all the strength into a single level is discussed. The distribution of strength due to non-constancy of radial integrals and non-degeneracy of unperturbed particle-hole orbits is demonstrated in “realistic” calculations for ²⁰⁸Pb, ¹³²Sn, ⁹⁰Zr and ⁵⁶Ni. The collection of low energy dipole strength into “mini-resonances” is shown to be sensitive to the mean energy difference between neutron and proton particle-hole states.     

Inelastic scattering of 13C from 40Ca and the L = 1 problem

Inelastic scattering to the first 3^?, 2⁺ and 5^? states of ⁴⁰Ca has been measured with a 68 MeV ¹³C beam. These data indicate that a recent theoretical attempt to reproduce the anomalous L=1 angular distribution in the ⁴⁰Ca(¹³C, ¹⁴N)³⁹K reaction with a coupled channels calculation overestimates the inelastic scattering to the 3^? and 5^? states in ⁴⁰Ca by factors of 2.4 and 5, respectively.     

II. The intermediate velocity source in the 40Ca + 40Ca reaction at Elab = 35AMeV

The shape of the velocity distributions of charged particles projected on the beam direction can be explained if emissions from the hot projectile-like fragment and the target-like fragment are supplemented by an emission from an intermediate velocity source located between them. The creation of this source is predicted by a two-stage reaction model where, in the second stage, some of the nucleons identified in the first stage as participants form a group of clusters located in the region between the colliding nuclei. The cluster coalescence process is governed on the average by the maximum value of entropy, although its fluctuations are also significant. The properties of the intermediate velocity source are precisely described, including the isotopic composition of the emitted particles. Received: 12 March 2001 / Accepted: 20 June 2001     

Elastic scattering of 40Ar on 40Ca at Elab = 191, 236 and 272 MeV

Cross sections for elastic scattering of ⁴⁰Ar on ⁴⁰Ca have been measured at energies E_lab = 191, 236 and 272 MeV employing position-sensitive detectors and the method of kinematical coincidences. The experimental data are first compared with the ordinary and the generalized Fresnel models. Only the generalized Fresnel model describes the experimental data well. An optical model analysis with a Woods-Saxon potential yields an energy independent set of parameters (V_R = ?21.76 MeV, r_OR = 1.37 fm, a_R = 0.45 fm; W₁ = ?13.69 MeV, r₀₁ = 1.40 fm, a₁ = 0.36 fm) very similar to the one found in ⁴⁰Ca-⁴⁰Ca scattering at corresponding energies. Values deduced for the total reaction cross sections for the three energies are in good agreement with those predicted by the generalized Fresnel model. The data are also compared with optical model calculations with the real part of the potential replaced by various microscopically determined potentials. The proximity, Fleckner-Mosel and the Krappe-Nix-Sierk potentials like the phenomenological optical model potential reproduce the measured data fairly well over several orders of magnitude.     

Comment on fusion cross sections in the40Ar+40Ca and40Ca+40Ca systems

Using a strongly mismatched transfer reaction,¹³⁸Ba (¹⁴C,¹⁵N), the spin orbit potential for¹⁵N projectiles has been derived in terms of the reaction asymmetry. The strength and sign of the L·S-potential are consistent with a previous determination using an (¹⁶O,¹⁵n) reaction; the signis opposite to that for nucleons and agrees with a model where the last P_1/2 nucleon is responsible for the L·S potential.     

Twists in Hopf algebras andRT 1 T 2=T 2 T 1 relations

LetR be a matrix unitary quasi-classical solution of the Yang-Baxter equation. Considering an associative algebra defined by the relationRT ₁ T ₂=T ₂ T ₁ we find a universal twistF such thatR is the image ofR=F ₂₁ F ⁻¹ in the vector representation. Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002.     

T=1 states in26Al

The resonance reaction²⁵Mg(p, γ)²⁶Al in the energy rangeE _p =300–400 keV was used to populate high-lying bound states in the self-conjugate nucleus²⁶Al. The existence of three resonances atE _p =304, 316 and 388 keV was verified, the spins of the ones at 316 and 388 keV were found to be 3^? and 2⁺, respectively. The spin of the bound level at 4,547 keV level was fixed to beJ ^π=2⁺. Several strong isovector Ml transitions were observed, which led toT=1 assignments for the levels atE _x =4,191, 4,547, 4,599, 5,141 and 5,542 keV. The results for excitation energies and values ofJ ^π,T together with previous experimental and theoretical data on²⁶Al and the neighboring |T _z |=1 nuclei²⁶Mg and²⁶Si are discussed in the framework of the isospin model.     

Monopole states in 40Ca

The τ = 1 and τ = 0 one-particle-one-hole monopole states in ⁴⁰Ca are calculated within the hydrodynamical model and with realistic forces and within the framework of the Migdal theory.     

The N = Z nuclide 74Rb with T,Iπ = 1, 0+

Improved experimental techniques have permitted the observation of the new nuclide ⁷⁴Rb with a half-life of 64.9 ± 0.5 ms, which represents the heaviest self-conjugate nucleus detected until now. The absenceof along-lived isomer indicates that the T = 0 state of ⁷⁴Rb lies a bove the T = 1 state. An upper limit of 10^?3 relative top ⁷⁴Rb can be placed on the yield of the (unobserved) mirror nucleus ⁷³Rb, and it appears likely that the limit of particle stability has been reached. The half-life of ⁷⁵Rb is 17.0 ± 1.0 s.     

Coulomb displacement energies of the T = 1, J = 0 states of A = 42 nuclei

Coulomb displacement energies of the T = 1, J = 0⁺ and 6₁⁺ states of A = 42 nuclei are analyzed with previously known charge dependent forces and effects, and with the available HartreeFock single-particle wave functions. From the study of the Coulomb displacement energies of the 6₁⁺ states, it is found that the present knowledge on the charge dependence, including a phenomenological charge symmetry breaking force previously introduced so as to help explain the Nolen-Schiffer anomaly, gives a sufficient and consistent explanation for both single-particle and twoparticle systems. From the study of the 0⁺ states, we found that the Coulomb displacement energies of the second 0₂⁺ states can be explained with a compensation between the smaller Coulomb energies of the second lowest two-particle state and larger ones of the deformed 4p-2h state.     

Untersuchung von40Ca mit der Reaktion39K(p, γ0)40Ca

Excitation functions of the reaction³⁹K(p, γ ₀)⁴⁰Ca at 0° and 90° have been taken in the proton energy range 2.5–6.0 MeV corresponding to an excitation of⁴⁰Ca between 10.8 and 14.1 MeV. Positions and strengths of several resonances appearing in the excitation functions are given. The structure of⁴⁰Ca is compared with predictions from 1 particle — 1 hole calculations.     

T = 1 effective interaction in the sd shell

The effective interaction in T = 1 two-body states in the sd shell is parameterized in terms of radial matrix elements of the effective potential in states of relative orbital angular momenta of two nucleons. Seven of these parameters are needed to define all the T = 1 matrix elements with the assumption of a central effective potential. The values of these parameters are determined by making a least-squares fit to 16 observed level energies in the oxygen isotopes and are then compared with values calculated from various realistic free nucleon-nucleon interactions. It is shown that a major effect of core excitation and consequent renormalization of the two-body matrix elements, so forcefully pointed out by Kuo and Brown, consists of a strong modification of the contributions of the triplet-odd force. Two-body matrix elements calculated with our parameters are also found to agree well with those determined by Glaudemans et al. from a least-squares fit to observed level schemes of nuclei with A = 29–40.     

Mode shaping in mixed ion crystals of 40Ca2+ and 40Ca+

We present studies of mixed Coulomb crystals of ⁴⁰Ca⁺ and ⁴⁰Ca²⁺ ions in a linear Paul trap. Doubly charged ions are produced by photoionization of trapped ⁴⁰Ca⁺ with a vacuum ultraviolet laser source and sympathetically cooled via Doppler cooled ⁴⁰Ca⁺ ions. We investigate experimentally and theoretically the structural configurations and the vibrational modes of these mixed crystals. Our results with ⁴⁰Ca²⁺ are an important step towards experimental realization of the proposals for mode shaping in a linear crystal and spin-dependent configuration changes from zigzag to linear as proposed by Li et al. (Phys Rev A 87:052304, 2013) and Li and Lesanovsky (Phys Rev Lett 108:023003, 2012) using ions excited to Rydberg states.