Large-angle correlations between /sup 4/He and /sup 1,2,3/H or /sup 4/He in the reactions 247 and 337 MeV /sup 40/Ar+/sup nat/Ag: Unexpected properties of the nuclear stratosphere

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.37.2561· OSTI ID:5226633

Lacey, R; Ajitanand, N N; Alexander, J M; de Castro Rizzo, D M; Peaslee, G F; Vaz, L C; Kaplan, M; Kildir, M; La Rana, G; Moses, D J; others, and

We have measured coincidences between /sup 4/He and /sup 1,2,3/H or a second /sup 4/He (large-angle correlations) in the reactions 247 and 337 MeV /sup 40/Ar+/sup nat/Ag. These coincidences are dominated by reactions leading to evaporation residues with spins of about 0--70(h2..pi..). Large values of the angle-integrated double and triple coincidence cross sections indicate that many particle evaporation chains involve 2 or 3 protons andor 2 or 3 alphas. The angular and energy distributions are well described by an evaporation model with Hauser-Feshbach coupling. However, one must employ effective evaporation barriers for /sup 1/H and /sup 4/He that are strongly reduced compared to empirical fusion barriers. The barrier reduction required for /sup 2/H is rather small, and for /sup 3/H no barrier reduction is needed. Evaporation calculations that include emitter deformation do not give a satisfactory explanation for these results. We suggest a new aspect of composite nucleus excitation and evaporation-like decay. A hot, very diffuse nuclear surface may be formed that promotes evaporative decay prior to its relaxation. The low barriers for /sup 1/H and /sup 4/He reflect the radial extent of this transitory, diffuse surface.

• Research Organization: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794
• OSTI ID: 5226633
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 37:6; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

651820* -- Nuclear Properties & Reactions
A=150-189
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
ANGULAR MOMENTUM
ARGON 40 REACTIONS
BARYONS
CHARGED PARTICLES
CHARGED-PARTICLE REACTIONS
COINCIDENCE SPECTROMETRY
COMPOUND-NUCLEUS REACTIONS
CROSS SECTIONS
DEFORMATION
DEUTERONS
DISTRIBUTION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY RANGE
ENERGY SPECTRA
EVAPORATION MODEL
EVEN-EVEN NUCLEI
FERMIONS
HADRONS
HAUSER-FESHBACH THEORY
HEAVY ION REACTIONS
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
METALS
MEV RANGE
MEV RANGE 100-1000
NUCLEAR DEFORMATION
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEAR THEORY
NUCLEI
NUCLEONS
PARTICLE PROPERTIES
PROTONS
SILVER
SPECTRA
SPIN
STABLE ISOTOPES
TRANSITION ELEMENTS
TRITONS