Transition probabilities and isospin structure in theN=Znucleus46V

Abstract

Picosecond lifetimes in 46 V and 46 Ti were determined using the recoil distance Doppler-shift technique with a plunger device coupled to a setup of five HP Ge detectors enhanced by one EUROBALL CLUSTER detector. The experiment was carried out using the 32 S( 16 O,pn) reaction at 38 MeV at the Cologne FN TANDEM facility. The differential decay curve method in coincidence mode was employed to derive lifetimes for five excited states in each nucleus. The resulting E2 transition probabilities are compared with existing shell model calculations and a comparison within the Tϭ1 isospin triplet is given. Absolute E1 strengths of the 2 Ϫ decay in 46 V are discussed.The investigation of NϭZ nuclei is an exciting topic in nuclear structure physics, to which a lot of experimental and theoretical work has been devoted recently. Self-conjugate nuclei are symmetric with respect to the isospin degree of freedom and allow a sensitive testing of the isospin symmetry. This symmetry leads to selection rules, e.g., E1 transitions between low lying states with Tϭ0 character are strictly forbidden. The only way to enhance E1 strengths between such states is to assume an admixture of Tϭ1 components of the wave function, caused by the Coulomb interaction or by isospin violating parts of the strong interaction.The determination of isospin mixing matrix elements via lifetime measurements is of special interest in odd-odd N ϭZ nuclei with valence particles in the f 7/2 shell. In 46 V, much interesting data have been accumulated recently ͓1-6͔. A very peculiar finding was the isospin forbidden 2 Ϫ →1 ϩ transition with a relative E1 strength six times stronger than the strength of a competing allowed one with ⌬Tϭ1 ͓1͔. In order to achieve a better comparison between allowed and forbidden E1 transitions, it is important to determine ͑more and͒ absolute transition probabilities in this nucleus. The present work reports on the decay properties of the 2 1 Ϫ ,T ϭ0 state and explains the observed relative E1 strengths.Aside from this, a comparison with 46 Ti, the isobaric analog partner of 46 V, is presented. In the Tϭ1 triplet the reduced E2 matrix elements have a linear dependence upon T z , which follows from general arguments based on the ideas of isospin symmetry ͓7͔, provided that isospin is a good quantum number. Precise B(E2;2 1 ϩ →0 ϩ ) values provide a stringent test to this theoretical relation. The new data are in better agreement with the theoretical description than a previous value.In 46 V recent model calculations in the full p f shell without any truncation for the positive parity states describe the experimental level order and branching ratios well ͓1͔. Nevertheless, reliable data on transition probabilities are necessary for an overall comparison of experimental data with shell model calculations. Despite its relevance such information is still scarce.We performed a recoil distance Doppler-shift ͑RDDS͒ experiment with the Köln coincidence plunger device ͓8͔ at the FN TANDEM facility at the University of Cologne. Excited states ...

Experimental evidence for56Ni-core breaking from the low-spin structure of theN=ZnucleusLisetskiy1, Pietralla2, Honma3 et al. 2003Phys. Rev. CSelf Cite

“…Recent progress in both experimental and theoretical directions brought new valuable data for the heavy odd-odd N = Z nuclei 46 V [4,5,6,13,14,15,16] , 50 Mn [7,17,18,19,20,21], and 54 Co [22,23,24,25] in the lower part of the pfshell (f 7/2 -shell) and even for some nuclei of the upper part of the pf -shell, like 70 Br [26,27]. While some understanding of the key problems of the low-energy structure of f 7/2 nuclei seems to be obtained and regularities similar to the ones appropriate for the sd-shell are revealed there are still many uncertainties for low-spin structure of these nuclei with mass numbers A > 56 [28,29,30,31,32,33,34,35].…”

High-resolution study of Gamow-Teller transitions from theTz=1nucleusTi46Adachi1, Fujita2, Brentano3 et al. 2006Phys. Rev. CSelf Cite430270View full textAdd to dashboardCite

“…The contribution of the orbital term, however, can be large if a nucleus is deformed, as was found for the A = 23 [52] and A = 25 [53] systems. As mentioned, for the A = 46 system a substantial quadrupole deformation of β ≈ 0.28 was suggested by the analysis of the γ transitions between the low-lying low-spin states [44]. Therefore, it is interesting to compare the strengths of analogous GT and M1 transitions.…”

“…The low-lying states in 46 V are described by an angular-momentum-coupled protonneutron pair or a quasideuteron (a generalized deuteron) made of the valence odd proton and neutron occupying Nilsson orbitals coupled to the rotating 44 Ti core. A recent γ -ray spectroscopy measurement for the low-lying region of 46 V [25,44] was described by this approach. The measured B(E2) values suggested a substantial quadrupole deformation of β ≈ 0.…”

Mixed symmetry states and isospin excitation in N = Z nucleus 52Fe

“…The subgroups U d (5), O sd (6) and SU sd (3), as in IBM-1, respectively describe vibrational, γ -unstable and rotational nuclei. Dynamical symmetries of IBM-3 have been studied in refs.…”

“…refs. [1 28], has been carried out recently for the investigation and understanding of the structure of the atomic nuclei with N = Z, the initial focus being on heavy odd-odd N = Z nuclei [1][2][3][4][5][6][7] . However, many experimental studies have been started recently for heavy even-even N = Z nuclei [9,11,13,24] (A≥40 up to A = 88).…”