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Energy dependence of GAMMA/sub f//GAMMA/sub n/ for the nucleus $sup 216$Rn

Conference ·
OSTI ID:4357283
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The /sup 209/Bi + /sup 7/Li reaction was used to determine experimentally GAMMA /sub f// GAMMA /sub n/ for the initial compound nucleus / sup 216/Rn. Cross sectio ns for the (/sup 7/Li,f) reaction were measured at bombarding energies between 24 and 34 MeV by detecting coincident fiasion fragments. All the other components of the total reaction cross section are due to (/sup 7/Li,xn), (/sup 7/Li,txn) and (/sup 7/Li, alpha xn) reactions. They wer e determined by observing known energy alpha particles from the short lifetime decays of various Rn, At and Po isotopes. The background due to prompt reaction particles was eliminated by using a pulsed (/sup 7/Li-beam and detecting the decay particles between beam pulses. Correction for the effects of second chance fission was obtained from measurements of cross sections for the (/sup 6/Li,f) and (/sup 6/Li,xn) reactions at approximate energies. The results give a direct measurement of GAMMA /sub f// GAMMA /sub n/ since both fission and neutron evaporation cross sections were determined. The experimental values of GAMMA / sub f// GAMMA /sub n/ for /sup 216/Rn and eariler data fo r /sup 210/Po are analyzed with a J dependent statistical model and the effect of incorporating an enhancement of the level density at the saddle point due to coupling to collective rotations is investigated. Fission barriers extracted with a variety of assumptions about the level densities are compared with theoretical predictions. (auth)

Research Organization:
Rochester Univ., N.Y. (USA). Nuclear Structure Research Lab.
NSA Number:
NSA-29-017277
OSTI ID:
4357283
Report Number(s):
COO--3496-30; CONF-730823--22; SM--174-56
Country of Publication:
United States
Language:
English

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Related Subjects

*BISMUTH 209-- LITHIUM 7 REACTIONS
*LITHIUM 7 REACTIONS-- FISSION
COINCIDENCE METHODS
COLLECTIVE MODEL
COMPOUND NUCLEI
COUPLING
DIFFERENTIAL CROSS SECTIONS
ENERGY LEVELS
EVAPORATION MODEL
EXCITATION FUNCTIONS
MEV RANGE 10-100
N68951 --Physics (Nuclear
Experimental)--Nuclear Properties & Reactions
190 <= A <= 219--Nuclear Reactions & Scattering
N68961* --Physics (Nuclear
Experimental)--Nuclear Properties & Reactions
190 <= A <= 219 Nuclear Reactions & Scattering--Spontaneous & Induced Fission
NUCLEAR POTENTIAL
RADON 216
ROTATIONAL STATES
TOTAL CROSS SECTIONS