Neutron Yield from (3-He,xn) Reactions on Thick Copper Targets

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

190 MeV Proton-Induced Fission

This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit

Masses from an inhomogeneous partial difference equation with higher-order isospin contributions

In the present work, a mass equation obtained as the solution of an inhomogeneous partial difference equation is used to predict masses of unknown neutron-rich and proton-rich nuclei. The inhomogeneous source terms contain shell-dependent symmetry energy expressions (quadratic in isospin), and include, as well, an independently derived shell-model Coulomb energy equation which describes all known Coulomb displacement energies with a standard deviation of [sigma]c = 41 keV. Perturbations of higher order in isospin, previously recognized as a cause of systematic effects in long-range mass extrapolations, are also incorporated. The most general solutions of the inhomogeneous difference equation have been deduced from a [chi]2-minimization procedure based on the recent atomic mass adjustment of Wapstra, Audi, and Hoekstra. Subjecting the solutions further to the condition of charge symmetry preserves the accuracy of Coulomb energies and allows mass predictions for nuclei with both N [ges] Z and Z > N. The solutions correspond to a mass equation with 470 parameters. Using this equation, 4385 mass values have been calculated for nuclei with A [ges] 16 (except N = Z = odd for A m = 194 keV from the experimental masses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27246/1/0000253.pd

Mass predictions from the Garvey-Kelson mass relations

Part A: The transverse Garvey-Kelson mass relation represents a homogeneous third-order partial difference equation. Procedures are described for estimating masses of nuclei with N [ges] Z from the most general solution of this difference equation subject to a [chi]2 minimization, using the recent atomic mass adjustment of Wapstra, Audi, and Hoekstra as a boundary condition. A judicious division of the input data into subsets of neutron-rich and proton-rich nuclei had to be introduced to reduce systematic errors in long-range extrapolations. Approximately 5600 mass-excess values for nuclei with 2 [les] Z [les] 103, 4 [les] N [les] 157, and N [ges] Z (except N = Z = odd for A m [approximate] 103 keV.Part B: The charge-symmetric mass relation of Kelson and Garvey for estimating masses of nuclei with Z > N and T [ges] 1 is described. The calculations make use of the experimental Coulomb energy differences between mirror nuclei for A [les] 59 and of estimated values for A > 59. Some 250 mass-excess values have been calculated. The standard deviation for reproducing the known values is [sigma]m [approximate] 231 keV.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27245/1/0000252.pd

Further Studies of Unusual Fission Mass Distributions using 190 MeV Protons

This research was sponsored by the National Science Foundation Grant NSF PHy 87-1440

190 MeV Proton-Induced Symmetric and Asymmetric Fission

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Measurement of alpha‐widths in 16O relevant to astrophysics

Several different α‐transfer reactions, 12C→16O, have been studied at high bombarding energies with magnetic spectrometers. Line‐widths, α‐spectroscopic factors, Sα, and reduced α‐widths, γα2 and ϑα2, have been determined for levels in 16O, including several of importance in astrophysics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87457/2/752_1.pd

A Study of the (3-He,t) Charge-Exchange Reaction at E(3-He) = 200 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Error propagation in extrapolated nuclear mass predictions

The properties of the error of the nuclear masses calculated from the transverse mass relations are analysed. The work assumes that the calculated errors of the nuclei whose masses are known experimentally behave as a sample selected randomly from a normal population having a zero mean and a standard deviation σ . It is found that the errors of the calculated masses of nuclei far from the line of beta-stability behave as c 1 d 3/2 where c 1 is a constant and d is the distance of the nucleus from the line of beta-stability. It is shown also that the errors related to the calculated mass differences behave as c 2 d 1/2 where c 2 is another constant.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45826/1/10050_2005_Article_BF01433618.pd

Pleistocene Brawley and Ocotillo Formations: Evidence for Initial Strike-Slip Deformation Along the San Felipe and San Jacinto Fault Zones, Southern California

We examine the Pleistocene tectonic reorganization of the Pacific–North American plate boundary in the Salton Trough of southern California with an integrated approach that includes basin analysis, magnetostratigraphy, and geologic mapping of upper Pliocene to Pleistocene sedimentary rocks in the San Felipe Hills. These deposits preserve the earliest sedimentary record of movement on the San Felipe and San Jacinto fault zones that replaced and deactivated the late Cenozoic West Salton detachment fault. Sandstone and mudstone of the Brawley Formation accumulated between ∼1.1 and ∼0.6–0.5 Ma in a delta on the margin of an arid Pleistocene lake, which received sediment from alluvial fans of the Ocotillo Formation to the west-southwest. Our analysis indicates that the Ocotillo and Brawley formations prograded abruptly to the east-northeast across a former mud-dominated perennial lake (Borrego Formation) at ∼1.1 Ma in response to initiation of the dextral-oblique San Felipe fault zone. The ∼25-km-long San Felipe anticline initiated at about the same time and produced an intrabasinal basement-cored high within the San Felipe–Borrego basin that is recorded by progressive unconformities on its north and south limbs. A disconformity at the base of the Brawley Formation in the eastern San Felipe Hills probably records initiation and early blind slip at the southeast tip of the Clark strand of the San Jacinto fault zone. Our data are consistent with abrupt and nearly synchronous inception of the San Jacinto and San Felipe fault zones southwest of the southern San Andreas fault in the early Pleistocene during a pronounced southwestward broadening of the San Andreas fault zone. The current contractional geometry of the San Jacinto fault zone developed after ∼0.5–0.6 Ma during a second, less significant change in structural style