Browsing by Subject "Fission neutron"

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    Fine structure of mass and charge distribution in low energy fission
    (Akademiai Kiado Rt., 1992) Erten, H. N.; Aras, N. K.
    Studies of finer details in mass and charge distribution fission leads to a better understanding of the fission process. Experimental determination of independent and cumulative yields using radiochemical techniques as well as mass spectrometers and fission product recoil separators form the basis of such studies. It has been established that closed shells as well as an even number of nucleons influence both mass and charge distributions. The magnitudes of these effects may be estimated from existing experimental yield data and various fission models. Using our measurements of several fission yields and those existing in the literature we have calculated even-odd proton and neutron effects for various low energy fissioning systems. Where enough data existed, direct calculations were made, whereas for other cases the Zp-model of WAHL has been used. It is found that the even-odd proton effect is well established and pronounced in thermal neutron fission of235U and233U. Lesser effects were found for reactor neutron induced fission of232Th, thermal neutron fission of239Pu and spontaneous fission of245Cm and249Cf. No effect seems to exist in the thermal neutron fission of241Pu and the spontaneous fission of252Cf. The even-odd neutron effect is found to be much lower than the corresponding proton effect in235U and233U fissions and is nonexistent in the rest of the fissioning systems.
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    Influence of even nucleon numbers and closed shells on mass and charge distribution in low energy fission
    (Kluwer Academic Publishers, 1994) Buyukmumcu, Z.; Erten, H. N.; Aras, N. K.
    Extensive experimental and evaluated yield data are now available for the fragments in low energy nuclear fission. Using these data we re-examined the influence of even nuclear numbers and closed shells on the mass and charge distribution in low energy fission. We used WAHL's Zp model and Ap model. We also examined the effects of Z=50, N=82 and possibly N=88 shells. A new method was developed based on two Gaussian curves for the even and odd products. The EOZ and EON values calculated are based on these different methods and are seen to be consistent with each other in spite of the somewhat different definitions of the even-odd effect. The even-odd effect decreases with an increasing fissility parameter. The EON values are substantially lower than the corresponding EOZ values, probably due to the effect of washing out the neutron pairing effect by prompt neutron emission. The magnitude of the even-odd effect varies with different mass regions. The EOZ and EON values decrease as they go from asymmetric to symmetric regions in mass distributions. © 1994 Akadémiai Kiadó.