Investigation of neutron deficient nuclei in the region 28<N, Z <50 with the help of heavy ion compound reactions

Abstract

In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:natCa +32S,natCa +40Ca,54Fe +14N,58Ni +12C,58Ni +14N,66Zn +16O,68Zn +16O. Level schemes of66Ge,68Ge,69As,70Se,74Kr,80Sr and82Sr have been deduced. The following level energies and spin-parity assignments have been found:66Ge: 957.4 keV, 2+; 1693.7; 2174.7, (4+); 3685.7; 4207.5;68Ge: 1015.8, 2+; 1777.9, 2+; 2267.9, 4+; 2428.8, 3(+); 2649.1, 3−; 3582.3, (5−); 3649.3, (5−); 3696.2, (6+); 3883.3, (6−); 4054.4, (7−); 4454.6; 4837.3;69As: 98.2; 164.6;789.6;863.2; 1306;2160;2210.4;2831.5;3258.3;3263.5;3991.1;5195.7;70Se: 945.4, 2+; 1600.9; 2039.4, (4+);74Kr: 455.7, 2+; 1013.5, (4+); 1781.5;80Sr: 385.4, 2+; 980.2, (4+); 1763.2, (6+);82Sr: 573.4, 2+; 1328.5,(4+); 2229.6,(6+). γ ray activity spectra have been measured after the bombardment of natural Ca with32S. The half-life of the new isotope69Se has been found to be 27±3 sec. Recoil distance Doppler-shift measurements have been performed with the reactions62,64Ni,66zn(16O, 2n)76, 78 Kr,80Sr. The following half-lives have been determined:76Kr: 423.8 keV, 2+, 37±5 psec; 1034.2,4+, 5.7±1.6;78Kr: 455.3, 2+, 25±3; 1120.0, 4+, 3.8±1;80Sr: 385.4, 2+, 44±6. The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near 38 76 Sr38 or 40 78 Zr38.