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Passing mass separated recoil fission particles through a AE Si-surface barrier detector the nuclear charge distributions of fission products were measured in the mass chains 79 to 100. The average nuclear charge as well as the second, third, and fourth moment of the nuclear charge distribution reveal odd-even and shell effects.NUCLEAR REACTION, FISSION U(n, h, f), measured nuclear charge distribution of A = 79 to A =100, deduced element and isotone yields, proton and neutron odd-even effect.

An intrinsic germanium detector was used to measure the beta endpoint energies of heavy fission products supplied by the on line mass separator OSTIS installed at the high flux reactor of the Institut Max von Laue-Paul Langevin, Grenoble. The endpoints of singles-spectra have been determined and, by means of beta-gamma coincidence measurements also most of the Ot~-values of the following neutron-rich nuclides could be deduced with high accuracy:

The beta-decay energy of 20 nuclides in the mass region 88 _

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The nuclear charge distribution of fission products from 235 U(w th ,/) is determined for the isobaric chains 92 to 100. The results were obtained from the energy loss of monoisobaric and monoenergetic fission products in a AE Si surface-barrier detector. The odd-even effect is found also in the mass chains reported here for the first time, revealing an approximately sinusoidal variation of the charge distribution width with mass.The fission products separated by "LOHENtheir nuclear charge; therefore, the method is in-GRIN" 1 according to mass and kinetic energy prodependent of any chemical or decay properties vide a unique means to measure the nuclear of the selected fission products. The efficiency charge distribution in fission, which is only known of this detector does not depend on the nuclear incompletely. The energy loss of these separated charge. With an 8-Lim-thick AE silicon detector fission products in a AE detector depends only on the achieved nuclear-charge resolving power Z/ TABLE I. The fractional independent fission yields and the average nuclear charge Z p for fission products of the isobaric chains 92 to 100 from 235 U(« th ,/). The yields in brackets are the FIY values (Ref. 3) Mass 92 93 94 95 96 97 98 99 35 Br 1.8±0.8 ( ) 0.7±0.5 ( o ) 36 K ' 28.7±1.5 ( ) 33.5±2.0 ( ) 15.0±2.2 ( ) 6.2±1.2 ( ) 39 Y 1.2±0.7 ( ) 2.1±0.7 (1.6±0.2) 5.9±0.8 (6.0±2.0) 14.8±1.5 (13.0±6.0) 31.6±2.5 ( ) : 50.3±2.0 ( ) 37.7+3.0 ( ) 35.5±2.5 ( • ) 40 Zr 0.9±0.7 ( .) 1.1±0.7 ( ) 0.8±0.5 ( ) 1.6±0.8 ( ) 3.5±0.8 ( ) 11.4±1.5 ( ) 43.4±3.0 ( ) 52.2±2.5 ( )41 Nb 1.1±0.8 ( ) 1.3±0.6 ( ) 3.Oil.5 ( ) 4.7±1.2 ( ) 42 Mo l.3±n. ( Z P 36.87 (36.79) 37.34 (37.41) 37.74 (37.79) 38.03 (38.03) 38.36 (38.35) 38.73 ( ) 39.33 ( ) .6 39.59 ) ( ) 100 0.9+0.5 7.9±1.2 84.6±3.0 5.7i0.9 0.9+0.5 39.98 ( ) ( ) ( ' ) ( ) ( ) ( ) 1034

Half-lives and delayed-neutron emission probabilities (P,) of short-lived Rb and Cs precursors in the mass chains 94 98 and 143 147 were measured. Sources of isotope separated nuclides were obtained from the on-line mass-separator OSTIS installed at the Grenoble high-flux reactor. A new P,-value of (25.4_+3.2)% is given for the (214_+30)ms ~TCs; the P,-values of nine alkali precursor nuclides were redetermined: (2,730_+20)ms 94Rb with (9.7_+0.

Half-life determinations of Rb and Cs fission products available at an on-line mass separator have been made for several neutron-rich Rb, Sr, Cs, and Ba isotopes using both P-multiscale and y-multispectra measurements. The half-lives and rms uncertainties (in sec) are Rb, 0.203+0.