RECOIL STUDIES OF NUCLEAR REACTIONS INDUCED BY HEAVY IONS

Journal Article · Sun Jan 15 04:00:00 EST 1961 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.121.529· OSTI ID:4086892

Alexander, J M; Winsberg, L

The mechanism of nuclear reactions induced by heavy ions was investigated by measuring the recoil ranges of Tb/sup 149/, At/sup 211/, and other alpha emitting isotopes of At and neighboring elements and by determining the cross sections for the formation of Tb/sup 149/ and At/sup 211/. Recoil ranges wer e consistent with compound-nucleus formation at all energies studied for the following reactions: Pr/sup 141/(C/sup 12/,4n)Tb/sup 1/ >s/sup 49/, Ce(N/ sup 14/.xn)Tb/sup 149/, La/sup 139/(O/sup 18/,bn)Tb/sup 1/ >s/sup 49/, La/sup 139/ (8/sup >/8n)Tbitl. and Ba(Ne/sup 22/.pxn)Tb/sup 149/. A similar result was obtained for th e reaction Pr/sup 141/(O/sup 16/,2p6n)Tb/sup 149/ at 138 and 14 6 Mev and for the reactions Au/sup 197/(O/sup 16/,2pxn, and 3pxn)At, Po at energies b elow 100 Mev. The excitation functions of the (HI.xn)Tb/sup 149/ reactions seemed to be characteristic of an evaporation process but had smaller peak cross sections than did the excitation functions of the reactions Ba(Ne/sup 22/,pxn)Tb/ sup 149/ or Pr/sup 1/ /sup 41/(O/sup 16/. 2p6n)Tb/sup 149/. It was concluded that most reactions probably involve charged-particle emission. The reaction Ba(Ne/sup 22/ pxn)Tb/sup 149/ seemed to occur with much greater probability than the reaction Ba(Ne/sup 20/,pxn)Tb/sup 149/. In many cases the compound-nucleus mechanism could not account for the results. Partial momentum transfer was observed in the reactions Au/sup 197/(O/sup 16/,2pxn, and 3pxn)At, Po at enengies above 100 Mev. Partial momentum transfer also occurred when Bi was bombarded at energies 1.3 times the barrier energy or greater. Reactions ot Bi with heavy ions (Ne/sup 20/ is a possible exception) at energies near the Coulomb barrier produced At/sup 211/ with greater recoil energy than expected from a compound- nucleus mechanism. Apparently particles were emitted in the backward direction. Near the barrier the cross section for the production of At/sup 211/ by C/sup 12/ , O/sup 1/ s/sup 6/, and Ne/sup 20/ bombardment comprised about one-fourth the value calculated for compound-nucleus formation. Therefore. the cross section for all noncompound-nucleus reactions must comprise a large fraction of the total interaction cross section. The experiments with Pb as a target were also consistent with this conclusion. (auth)

• Research Organization: Univ. of California, Berkeley
• NSA Number: NSA-15-010063
• OSTI ID: 4086892
• Report Number(s): UCRL-9118; 0031-899X
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 121; ISSN PHRVA
• Country of Publication: United States
• Language: English

Related Subjects

ALPHA PARTICLES
ANGULAR DISTRIBUTION
ANISOTROPY
ASTATINE
ASTATINE 211
ATOMS
BARIUM
BISMUTH
CARBON 12
CERIUM
COMPOUND NUCLEI
CROSS SECTIONS
ELECTRIC POTENTIAL
EMISSION
ENERGY
ENERGY RANGE
EXCITATION
EXCITATION FUNCTION
GOLD 197
HYDROGEN
ION BEAMS
IONS
ISOTOPES
LANTHANUM 139
LEAD
MEASURED VALUES
MOMENTUM
NEON 20
NEON 22
NEUTRONS
NITROGEN 14
NUCLEAR REACTIONS
NUCLEI
OXYGEN 16
OXYGEN 18
PHYSICS
POLONIUM
PRASEODYMIUM 141
PROTONS
RECOILS
SLOWDOWN
TARGETS
TERBIUM 149