ISOMER SPECTROSCOPY OF 127 Cd

1. ISOMER SPECTROSCOPY OF 127Cd F.Naqvi,1,2 M. Górska,2 L. Cáceres,2,3 A.Jungclaus,3 M. Pfützner,4 H. Grawe,2 S. Pietri,2 P. H Regan,5 D. Rudolph,6 Z. Podolyák,5 K. Andgren,7 T. Beck,2 B. Bednarczyk,2,8 J. Benlliure,9 G. Benzoni,10 A.M. Bruce,11 E. Casarejos,9 B. Cederwall,7 F. Crespi,10 P. Detistov,12 Zs. Dombrádi,13 P. Doornenbal,2 H. Geissel,2 J. Gerl,2 J. Grębosz,2,8 B. Hadinia,7 M. Hellström,6 R. Hoischen,2,6 G. Ilie,1 J.Jolie,1 A. Khaplanov,7 I. Kojouharov,2 M. Kmiecik,8 R. Kumar,14 N. Kurz,2 S. Lalkovski,11,12 A. Maj,8 S. Mandal,15 V. Modamio,3 F. Montes,2 S. Myalski,8 W. Prokopowicz,2 P.Reiter,1 H. Schaffner,2 G. Simpson,16 D.Sohler,13 S.J. Steer,5 S. Tashenov,2 J. Walker,3 H.J. Wollersheim2 & O. Wieland10 1Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany. 2Gesellschaft für Schwerionenforschung (GSI), D-64291 Darmstadt, Germany 3Departamento de Física Teórica, Universidad Autónoma de Madrid, E-28049 Madrid, Spain. 4IEP,Warsaw University, PL-00681 Warsaw, Poland. 5Department of Physics, University of Surrey, Guildford, GU2 7XH, UK. 6Department of Physics, Lund University, S-22100 Lund, Sweden. 7KTH Stockholm, S-10691 Stockholm, Sweden.. 8The Henryk Niewodniczański Institute of Nuclear Physics, PL-31342 Kraków, Poland. 9Universidad de Santiago de Compostela, E-175706 Santiago de Compostela, Spain. 10INFN, Universitádegli Studi di Milano and INFN Seizone di Milano,I-20133 Milano, Italy. 11School of Engineering, University of Brighton, Brighton, BN2 4GJ, UK. 12Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria. 13Institute National Polytechnique de Grenoble , F – 98026 Grenoble Cedex , France 14Inter University Accelerator Centre, New Delhi, India. 15University of Delhi, New Delhi, India. 16Institut Laue-Langevin, F-38042 Grenoble, France. MOTIVATION: • 48Cd79 is a neutron rich nucleus which has 3 neutrons and 2 protons • less than the doubly magic 132 Sn . The latter nucleus is a benchmark for • nuclear structure investigations. • Systematics of the Cd isotope chain shows evolution of neutron single particle • energy levels. • The observed neutron single particle evolution helps in determining the • monopole interaction used in SM calculation . • The comparison of theoretical predictions and experimental results provides • a means for understanding the structure of neutron rich isotopes below 132Sn • and possible on-set of collectivity. 127 EXPERIMENTAL TECHNIQUE: • RESULTS: • Singles Gamma Spectra • Five gamma energy transitions were • observed with energies739 keV, 822 keV , 712 keV 849 keV and 111 keV • γ –γ Coincidence Spectra • Life time measurement Bρ-ΔE-Bρ method (Achromatic Mode) FRAGMENT SEPARATOR • 127 Cd was produced both • in fragmentation of 136 Xe • beam @ 750 MeV/u and in • fission of 238U beam @ • 650 MeV/u .The intensities • of the beams were • ~ 7.4 X 108 ions/s and • ~ 2.7 X 108 ions/s • respectively • 9Be targets of thickness • 1g/cm2 and 4g/cm2 were • used for fission and • fragmentation of 238U and • 136Xe beams respectively DIPOLE : Bρ • In achromatic mode the fragments with same A/Q ratio are • focused at the same position on the final focal plane • Z Measurement • Energy loss in two MUlti • Sampling Ionisation Chambers • at S4 • Gamma coincidence spectra gated on • 739 keV TOF : βγ • A/Q Measurement • Time of flight measurement • between scintillators Sc21 at • S2 and Sc42 at S4 Identification plot • Time distribution obtained by summing the • gates at 712 keV, 739 keV, 821 keV, and • 849 keV on the energy vs time matrix • A maximum likelihood fit gives a half life • of T1/2 = 17.5(3) µs Energy and lifetime information from the gamma array • 15 Euroball cluster detectors • with 7 crystals each • Photopeak efficiency ~ 15 % • at 1 MeV RISING gamma array • The decay of yrast (19/2+) isomer was observed in 127Cd. • Based on the measured half-life T1/2 = 17.5(3)µs , primary decay • transitions were assigned to be an E3 of 849 keV and M2/E3 of 739 • keV. • Shell Model calculation predicted the existence of (19/2+) isomer of a similar • half life in 127Cd . A calculation using the E3 strength of the neighbouring • 129Sn isotone gives similar life time supporting the spin assignment . • The energy of 13/2- state ,obtained in Shell Model calculation is too • high compared to the experiment value . Hence, a modification • of the monopole interaction used in the calculation is required. CONCLUSIONS: Proposed level scheme and shell model prediction SM EXP