Half-life of the I Π = 4 - intruder state in 34 P: M 2 transition strengths approaching the island of inversion

The half-life of the 2305-keV, I?=4 (-) intruder state in 34P has been measured as t 1/2=2.0(1) ns using ?-ray coincidence, fast-timing techniques with the Bucharest HPGe and LaBr 3:Ce detector array. Excited states in 34P were populated using the 18O (18O,pn )34P fusion-evaporation reaction at a beam energy of 36 MeV. Reduced transition probabilities have been calculated for different values of the M2/E3 mixing ratio, ? E3/M2, and compared with shell-model estimates. For small values of the mixing ratio, the B(M2) value was found to be consistent with similar transitions associated with the occupation of neutron f 7/2 configurations in this mass region. � 2012 American Physical Society

EXCITATION-FUNCTIONS OF THRESHOLD REACTIONS ON SC-45 AND MN-55 INDUCED BY 6 TO 13 MEV NEUTRONS

Excitation functions were measured for the Sc-45(n,2n)Sc-44(m), Sc-45(n,2n)Sc-44(m+g), and Mn-55(n,2n)Mn-54 reactions from threshold to 13 MeV, and for the Sc-45(n,p)Ca-45, Sc-45(n,alpha)K-42, Mn-55(n,p)Cr-55, and Mn-55(n,alpha)V-52 reactions over the neutron energy range of 6 to 13 MeV. The quasimonoenergetic neutrons were produced via the H-2(d,n)He-3 reaction using a deuterium gas target at a variable energy compact cyclotron. The activation technique in combination with high resolution gamma-ray spectroscopy was used. In the case of the Sc-45(n,p)Ca-45 and Mn-55(n,p)Cr-55 reaction products, ''low-level'' beta(-) counting was applied. The reaction product Ca-45 was separated radiochemically prior to beta(-) counting. Statistical model calculations taking into account precompound effects were performed for all the reactions studied. The experimental excitation functions are reproduced well by the calculation except for the (n,alpha) reaction on the (SC)-S-45 target

The effect of valence neutrons on spin-orbit splitting

We study the splitting of single-particle energies between spin-orbit partners (Is splitting) for the isotopic chains of some even-even closed shell nuclei in the Hartree-Fock-Bogolyubov framework. Z = 8, 20, 28 and 50 magic proton nuclei of stability valley and their even-even neighbours are selected and a limited systematic investigation is performed for the isotopic chains of C, O, Si, Ca, Ni, Sr, Sn, Te, and Ce isotopes. They are compared with existing data. The modification of proton spin-orbit partners energy splitting of those isotopes is investigated with valence neutron numbers extending to the neutron drip-line. Our calculation shows that the proton Is splitting in chosen nuclei becomes smaller with the increasing neutron number. This reduction is accounted for two different effects, namely, the effect of neutron diffuseness and tensor interaction. The neutron diffuseness values are also calculated for the nuclei under investigation. The deduced ls splitting reduction is compared for the nuclei with the same isospin number. The larger reduction is attributed to the tensor interaction assuming that the Is reduction due to the neutron surface thickness will be the same for the nuclei having the same neutron diffuseness parameter. The contribution from tensor interaction is mainly accounted for the interaction between the spin-orbit partner proton orbital and the neutron orbital having different angular momentum. Briefly, the effect of increased valence neutron number on proton effective single particle levels is discussed