L. Popescu

Measurement of the first ionization potential of astatine by laser ionization spectroscopy

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.

Observation of the β-delayed γ-proton decay of (56)Zn and its impact on the Gamow-Teller strength evaluation.

We report the observation of a very exotic decay mode at the proton drip line, the β-delayed γ-proton decay, clearly seen in the β decay of the T_{z}=-2 nucleus ^{56}Zn. Three γ-proton sequences have been observed after the β decay. Here this decay mode, already observed in the sd shell, is seen for the first time in the fp shell. Both γ and proton decays have been taken into account in the estimation of the Fermi and Gamow-Teller strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Studies on the double-β decay nucleus Zn64 using the (d,He2) reaction

The (d, 2 He) charge-exchange reaction on the double-β decay (ββ) nucleus 64 Zn has been studied at an incident energy of 183 MeV. The two protons in the 1 S 0 state (indicated as 2 He) were both momentum analyzed and detected simultaneously by the BBS magnetic spectrometer and its position-sensitive detector. 2 He spectra with a resolution of about 115 keV (FWHM) have been obtained allowing identification of many levels in the residual nucleus 64 Cu with high precision. 64 Zn is one of the rare cases undergoing a ββ decay in β + direction. In the experiment presented here, Gamow-Teller (GT + ) transition strengths have been extracted. Together with the GT - transition strengths from 64 Ni( 3 He,t) data to the same intermediate nucleus 64 Cu, the nuclear matrix elements of the ββ decay of 64 Zn have been evaluated. Finally, the GT + distributions are compared with shell-model calculations and a critical assessment is given of the various residual interactions presently employed for the pf shell.

β Decay of the exotic Tz=-2 nuclei Fe 48, Ni 52, and Zn 56

S. E. A. Orrigo, ∗ B. Rubio, Y. Fujita, 3 W. Gelletly, 4 J. Agramunt, A. Algora, 5 P. Ascher, B. Bilgier, B. Blank, L. Cáceres, R. B. Cakirli, E. Ganioğlu, M. Gerbaux, J. Giovinazzo, S. Grévy, O. Kamalou, H. C. Kozer, L. Kucuk, T. Kurtukian-Nieto, F. Molina, 9 L. Popescu, A. M. Rogers, G. Susoy, C. Stodel, T. Suzuki, A. Tamii, and J. C. Thomas Instituto de F́ısica Corpuscular, CSIC-Universidad de Valencia, E-46071 Valencia, Spain Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan Department of Physics, University of Surrey, Guildford GU2 7XH, Surrey, UK Inst. of Nuclear Research of the Hung. Acad. of Sciences, Debrecen, H-4026, Hungary Centre d’Etudes Nucléaires de Bordeaux Gradignan, CNRS/IN2P3 Université de Bordeaux, 33175 Gradignan Cedex, France Department of Physics, Istanbul University, Istanbul, 34134, Turkey Grand Accélérateur National d’Ions Lourds, CEA/DSM CNRS/IN2P3, BP 55027, F-14076 Caen, Cedex 5, France Comisión Chilena de Enerǵıa Nuclear, Casilla 188-D, Santiago, Chile SCK.CEN, Boeretang 200, 2400 Mol, Belgium Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA The results of a study of the beta decays of three proton-rich nuclei with Tz = -2, namely Fe, Ni and Zn, produced in an experiment carried out at GANIL, are reported. In all three cases we have extracted the half-lives and the total β-delayed proton emission branching ratios. We have measured the individual β-delayed protons and β-delayed γ rays and the branching ratios of the corresponding levels. Decay schemes have been determined for the three nuclei, and new energy levels are identified in the daughter nuclei. Competition between β-delayed protons and γ rays is observed in the de-excitation of the T = 2 Isobaric Analogue States in all three cases. Absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. In addition, we discuss in detail the data analysis taking as a test case Zn, where the exotic β-delayed γ-proton decay has been observed.

High resolution study of the Gamow–Teller strength distribution starting from the ground state of 14N in the β− and β+ directions

The two charge exchange reactions 14N(d, 2He)14C and 14N(3He, t)14O were studied with high resolution in order to identify the Gamow–Teller (GT) strength distribution starting from the ground state (g.s.) of 14N in the β− and β+ directions. The isospin symmetry in the A = 14 mass system is investigated. An overview of the main features of the experimental investigation is summarized here.

Observation of the 2+ isomer in Co52

We report the first observation of the 2

Splitting of the Pygmy Dipole Resonance

^+

βdecay of the exoticTz=−2nucleiFe48,Ni52, andZn56

isomer in

Beta decay of the exotic

^{52}

T_z

Co, produced in the