Search results for "fission"

Absence of delayed fission in the? ?-decay of 2.3 min238Pa

1985

We have searched for beta-delayed fission in the decay of 2.3 min238Pa produced in the238U(n,p) reaction with 14.7 MeV neutrons. Through microprocessor-controlled chemical separations of protactinium about 109 atoms of238Pa were isolated and exposed to fission track detectors. From the absence of fission tracks an upper limit for the betadelayed fission probability of238Pa, i.e.Pβf<2.6 10−8, is obtained at 95% confidence level. This rules out positive evidence for this decay mode of238Pa reported elsewhere. Simple theoretical estimates ofPβf range from 10−7 to 10−9.

Fusion-fission in the reaction76Ge+170Er

1984

Radiochemical yield measurements were performed to study mass- and charge distributions in the reaction of76Ge ions with170Er in the c.m. energy range from 222 MeV through 272 MeV. The magnitude of the resulting cross-section for fusion-fission is significantly lower than expected and is explained within the framework of Swiatecki's Extra-Push model.

Entry distribution of 220Th: A method to determine the fission barrier of an unstable nucleus

2001

Independent Isotopic Product Yields in 25 MeV and 50 MeV Charged Particle Induced Fission of 238U and 232Th

2014

Abstract Independent isotopic yields for most elements from Zn to La in 25-MeV proton-induced fission of 238U and 232Th have been determined at the IGISOL facility in the University of Jyvaskyla. In addition, isotopic yields for Zn, Ga, Rb, Sr, Zr, Pd and Xe in 50-MeV proton-induced fission of 238U and for Zn, Ga, Rb, Sr, Cd and In in 25-MeV deuterium-induced fission of 238U have been measured. The utilised technique recently developed at the University of Jyvaskyla, is based on a combination of the ion guide technique and the ability of a Penning trap to unambiguously identify the isotopes by their atomic mass. Since the yields are determined by ion counting, no prior knowledge beyond the …

Impact of TAGS Measurement on FP Decay Data and Decay Heat Calculations

2011

Discovery of New Fission Product Activities in the A=110–118 Mass Region

1986

Neutron rich nuclei around the mass A=100 have recently attracted both theoretical and experimental interest since they are expected to form a new region of strong deformation. In contrary, very little experimental information is available in the adjacent transitional region A= 110–118. Due to expected isomerism in this region both low and high spin states can be studied via beta decay in many nuclei. The studies of these nuclides have many experimental difficulties. They are only weakly produced in thermal neutron induced fission and because all the elements in this mass region (Tc, Ru, Rh, Pd) have very high melting points they have not been available as beams of on-line isotope separator…

Relevance of β-delayed neutron data for reactor, nuclear physics and astrophysics applications

2023

Initially, yields (or abundances) and branching ratios of β-delayed neutrons (βdn) from fission products (Pn-values) have had their main importance in nuclear reactor control. At that time, the six-group mathematical approximation of the time-dependence of βdn-data in terms of the so-called "Keepin groups" was generally accepted. Later, with the development of high-resolution neutron spectroscopy, βdn data have provided important information on nuclear-structure properties at intermediate excitation energy in nuclei far from stability, as well as in nuclear astrophysics. In this paper, I will present some examples of the βdn-studies performed by the Kernchemie Mainz group during the past th…

Search for Superheavy Elements in theU238+U238Reaction

1980

A search was made for spontaneously fissioning superheavy elements in damped collisions of two uranium nuclei. Different techniques were applied covering the elements 108 to 118 and approx. =126, and a half-life range from 1 ms to more than 1 yr. No evidence for superheavy elements was found at upper cross-section limits of 10/sup -32/, 10/sup -33/, and 10/sup -35/ cm/sup 2/ for half-lives from 1 to 100 ms, 100 ms to 1 d, and 1 d to 1 yr, respectively.

Stability and decay of nuclei at the end of the periodic system

1992

Abstract Recent studies of nuclear mass models show that it is essential to account for the Coulomb redistribution energy when calculating the nuclear potential energy in the heavy-element region. Results obtained by use of a mass model that includes Coulomb redistribution effects are analyzed. Q -values for α- and β-decay are calculated. Half-lives for α-decay are estimated by use of the Viola-Seaborg systematics. For EC, β + decay and β − decay, half-lives are calculated in a microsciopic QRPA model. Calculated single-particle level structures in the heavy-element region are presented. These indicate possible regions of isomers that would be unusually stable with respect to spontaneous fi…

First observation of nonyrast levels inZr103and level systematics ofN= 63 Sr, Zr, and Mo isotones

1996

The {beta} decay of the very-neutron-rich nucleus {sup 103}Y has been studied at the isotope separator IGISOL, allowing for the first time the observation of nonyrast levels in its daughter {sub 40}{sup 103}Zr{sub 63}. The level structure is similar to that of its isotones {sup 101}Sr and {sup 105}Mo, suggesting a large ground-state deformation of {beta}{approx_equal} 0.4. Level systematics allows for new level assignments in both {sup 103}Zr and {sup 105}Mo. {copyright} {ital 1996 The American Physical Society.}