Calculation of T=2 → T=1 → T =0 M1 decays in A =20 and A =32 nuclei

Absolute strenghts and branching ratios are calculated for M1 transitions between states of different isospin in two A = 4n nuclei of the sd-shell.     

Extended shell-model calculations for the A = 6 nuclei

Extended shell-model calculations for the A = 6 nuclei using the Sussex matrix elements and the Gogny et al. potential are presented. The results are discussed in connection with those obtained in the framework of the lowest order shell-model configurations.     

A weak coupling calculation for the A = 14 nuclei

A calculation of the A = 14 levels is performed by using the weak coupling approach. Very good agreement with experiment is obtained as all known levels below 13 MeV in ¹⁴N are satisfactorily explained. A few additional states are predicted to be found. The electromagnetic transition strengths are calculated and reproduce the experimental values in almost all cases. In particular, a simple calculation of the isospin mixture of the negative-parity states provides an explanation of the known T-forbidden E1 transitions. Also the reduced proton widths are considered and are found to be consistent with (p, p) scattering experiments on ¹³C.     

“Exact” shell model calculations in A = 17 and A = 18 nuclei and effective operators in the (2s, 1d) shell

A shell model calculation in an enlarged space spanned by two particles in the (2s, 1d) shell and three-particle-one-hole $\text{2}\text{h}\text{?}\text{ω}$ excitations is performed using the “bare” G-matrix. An effective interaction for the (2s, 1d) shell is generated and its convergence properties are investigated. It is maintained that the series converges reasonably fast in G and that the singleparticle energies used in the calculation are instrumental in this respect. This conclusion is corroborated by the E2 effective charges and B(E2) strengths that we compute for A = 17 and A = 18 nuclei respectively.     

Magnetic susceptibilities of polycrystalline samples of the compounds ANiCl3 (A = RB,NH4, Tl,Cs) and ANiBr3 (A = Rb,Cs)

The susceptibilities of polycrystalline samples of various antiferromagnetic linear-chain compounds ANiX₃ (A =Tl, NH₄, Rb, Cs and X = Cl, Br) have been measured in the temperature region 2–200 °K. The results, amongst which the already known data for RbNiCl₃ and CsNiCl₃, are interpreted in terms of a theory, developed by Weng, for antiferromagnetic Heisenberg linear-chain systems with spin S = 1. By means of Oguchi's Green function theory and the experimentally determined transition temperatures T_N the order of magnitude of the ratio between inter- and intra-chain interaction is obtained.     

6He β-decay from a three-body model of the A=6 system

The rate of ⁶He β-decay is computed from ⁶He and ⁶Li separable-potential three-body wave functions. The value of ft predicted with the wave functions derived from the most complete set of αN and NN interactions is 807±12 s compared to the experimental value of 807±2 s.     

No evidence for precritical phenomena of pion condensation in A = 48 nuclei

The ⁴⁸Ca(e,e′)(1⁺, 10.24 MeV) reaction, the ⁴⁸Ca(p,p′)(1⁺, 10.24 MeV) reaction and the ⁴⁸Ca(p,n)⁴⁸Sc(1⁺, 16.8 MeV) reaction have been theoretically investigated with respect to the occurrence of precritical phenomena related to pion condensation. No evidence for precritical phenomena is found.     

Investigation of the deep interior of the α-nucleus interaction around A = 40

A model-independent analysis of elastic α-particle scattering from ⁴⁰Ca between 22 and 142 MeV, and from ^36,40Ar, ^42,44,48Ca at 29 MeV is presented. The energy and mass dependence of the extracted optical potentials is discussed.     

Time resolved spectroscopy of KCl:Pb2+ excited in the A absorption band

By using a single photon-time correlation technique, time resolved emission spectra of the three time components are investigated in KCl:Pb excited in the A absorption band. The results, obtained in the temperature range 80–300 K, are discussed on the basis of the available theoretical models and of the effect of the charge compensating vacancy.     

Relation between the EPR linewidths and the exchange integrals in ACrO2 (A = Li, NaandK)

The temperature dependence of the peak-to-peak EPR linewidth (ΔH_p-p) of the ACrO₂ (A = Li, Na, K) compounds in the X-band is typical for the previously observed antiferromagnetic interactions. All three oxides show a single absorption line with a lorentzian shape. As expected the room temperature values of ΔH_p-p in the Q-band are very close to those obtained in the X-band. Using the Anderson-Weiss model for exchange-narrowed Lorentzian lines and the high-temperature limit values for ΔH_p-p 's of all three oxides it was possible to estimate the coefficient relating the exchange integrals between the adjacent Cr³⁺-ions in the cationic sublattice to the corresponding exchange fields and the coefficient relating the crystal-field parameters of Cr³⁺-ions to the second moments of the spectral lines.