883 research outputs found
Synthesis of new neutron-rich heavy nuclei: An experimentalist's view
I attempt to experimentally evaluate the prospects of synthesizing new
neutron- rich superheavy nuclei. I consider three possible synthetic paths to
neutron- rich superheavy nuclei: (a) the use of neutron-rich radioactive beams.
(b) the use of damped collisions and (c) the use of multi-nucleon transfer
reactions. I consider the prospects of synthesizing new n-rich isotopes of
Rf-Bh using light n-rich radioactive beams and targeted beams from ReA3, FRIB
and SPIRAL2. For the damped collision path, I present the results of a study of
a surrogate reaction, 160Gd + 186W. These data indicate the formation of Au
(trans-target) fragments and the depletion of yields of target-like fragments
by fission and fragment emission. The data are compared to predictions of
Zagrebaev and Greiner. For the multi-nucleon transfer reactions, the results of
a study of the 136Xe + 208Pb reaction are discussed. I consider the possibility
of multi-nucleon transfer reactions with radioactive beams
An experimentalist's view of the uncertainties in understanding heavy element synthesis
The overall uncertainties in predicting heavy element synthesis cross
sections are examined in terms of the uncertainties associated with the
calculations of capture cross sections, fusion probabilities and survival
probabilities. Attention is focussed on hot fusion reactions. The predicted
heavy element formation cross sections are uncertain to at least one order of
magnitude
Going Some : March Two Step
https://digitalcommons.library.umaine.edu/mmb-ps/1797/thumbnail.jp
Relativistic effects for the reaction Ubq + 6 CO = Ubq (CO)6 or Ubq (OC)6:Prediction of the existence, atomization energy, and isomerization energy of the isomers Ubq (CO)6 and Ubq (OC)6 of element Ubq ( Z=124, eka-uranium)
Our ab initio all-electron relativistic Dirac*Fock (DF) calculations for the
octahedral (Oh) Ubq(CO)6 and Ubq(OC)6 predict atomization energies (Ae) of
50.25 (47.93) and 43.43 (44.88 ) eV, respectively where the corresponding
non-relativistic calculated Ae's are given in parenthesis. Our calculated DF
and NR isomerization energies (E iso) for Ubq (CO) 6 = Ubq (OC) 6 are 6.83 and
3.05 eV, respectively. Our calculated DF (NR) energy for the reaction Ubq + 6CO
= Ubq (CO)6 is -4.31 (-4.30) eV, while the energy of the isomeric reaction Ubq
+ 6CO = Ubq(OC)6 is 2.52 ( -1.25 ) eV, respectively. The relativistic effects
increase the Eiso of Ubq (CO)6 by ~3.78 eV , decrease the Ubq-C bond distance
by 0.12 angstroms and have a negligible effect on the C-O bond distance as
expected. These are the first results of relativistic effects for isomerztion
energy and atomization energy of the superheavy Ubq (CO)6 and Ubq(OC)6. The
bond distances Ubq-C and Ubq-O optimized at the DF level of theory for Ubq(CO)6
and Ubq(OC)6 are 2.572 and 2.559 angstroms, while the corresponding optimized
bond distances Ubq-C and Ubq-O at the NR level of theory are 2.691 and 3.616
angstroms, respectively. Both our DF and NR calculations clearly predict the
formation of both the isomers Ubq(CO)6 and Ubq(OC), and the former is predicted
to be more stable at the DF level of theory by ~7 eV than the latter.No such
calculations have been reported before for systems of such superheavy elements.Comment: The present calculations do not include electron correlation effects
which are very significant but their accurate calculation would require an
order of magnitude computational expense as compared to the present
relativistic calculation
Ferns and Flowers : Waltzes
https://digitalcommons.library.umaine.edu/mmb-ps/2514/thumbnail.jp
Heavy Residue Formation in 20 MeV/nucleon 197Au + 90Zr collisions
The yields and velocity distributions of heavy residues and fission fragments
from the reaction of 20 MeV/nucleon 197Au + 90Zr have been measured using the
MSU A1200 fragment separator. A bimodal distribution of residues is observed,
with one group, resulting from peripheral collisions, having fragment mass
numbers A=160-200, while the other group, resulting from ``hard'' collisions,
has A=120-160. This latter group of residues can be distinguished from fission
fragments by their lower velocities. A model combining deep-inelastic transfer
and incomplete fusion for the primary interaction stage and a statistical
evaporation code for the deexcitation stage has been used to describe the
properties of the product distributions.Comment: 19 pages, 6 figures, preprint submitted to Nucl. Phys.
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