Abstract No:	026
Submitted on:	3 Jan 2001, 11:25 GMT
Title:	Lifetimes and transition probabilities of low-lying positive parity states in 120Xe and 118Te
Author(s):	A.A Pasternak,1 J. Srebrny,2 T. Morek,2 Ch.Droste,2 Y.Sasaki,3 M.Oshima,3 A.D. Efimov,1 V.M. Mikhailov,1 E.O. Podsvirova,1 S. Juutinen,4 and G.B. Hagemann5
Affiliation(s):	1A.F.Ioffe Physical Technical Institute RAS, St.-Petersbourg, Russia, 2Nuclear Physics Division, IEP, Warsaw University, Warsaw, Poland, 33Tandem Accelerator Center,University of Tsukuba, Japan, 4Department of Physics, University of Jyväskylä, Jyväskylä, Finland, 5The Niels Bohr Institute, Copenhagen, Denmark

Lifetimes of 22 positive parity states in ¹²⁰Xe have been measured by the Doppler Shift Attenuation Method(DSAM) using the ¹¹¹Cd(¹²C,3n) reaction at a beam energy of 56 MeV. The experiment was performed at the JAERI Tandem Accelerator (Japan). The - coincidences were collected by the GEMINI array. Lifetimes of the 8 ground state band levels of ¹¹⁸Te up to I=16⁺ and 2 other levels have been measured by DSA and Recoil Distance (RD) methods using the ¹⁰⁹Ag(¹³C,p3n) reaction at a beam energy of 54 MeV. The experiment was performed at TAL NBI (Danmark). The - coincidences were colected by the NORDBAL array.

New methodical approache of lifetime determination based on the lineshape analysis of coincidence spectra has been applied for both nuclei in the case of the DSA and RD methods. In the case of RDM, lifetime was determined by analysis of the shape of full line (unshifted and shifted components together) - Recoil Distance Doppler Shift Attenuation method [1]. The B(E2) values which have been measured in ¹¹⁸Te give us the unique possibility to analyse E2 transition probabilities in the ground state collective band above the band crossing (see right panel of figure). In case of ¹²⁰Xe the B(E2) values along the yrast band are presented in the left panel of figure. The energies of the levels and E2 transition probabilities are interpreted in the framework of a new version of IBFM(IBM + 2q.p.) [2]. In this approache it was assumed, that the boson number increases with angular momentum. A satisfactory description of the level structure and B(E2) behaviour along the ground state, and 2-qp bands is achieved for ¹²⁰Xe and ¹¹⁸Te isotones.

Bibliography

1

J. Srebrny et. al, Nuclear Physics A (2001), in print.

2

A.D.Efimov et. al, contribution to this conference.