Radiochemical study of the medium energy pion double charge exchange reactions: /sup 209/Bi(pi/sup +/pi/sup -/)/sup 209-x/At

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1980

OSTI ID:6085628

Clark, J L

Carrier-free radiochemical techniques have been used to measure cross sections for the double charge exchange reactions of the type /sup 209/Bi(pi/sup +/, pi/sup -/xn)/sup 209-x/At for 100, 180, and 300 MeV incident pions. The observed formation of astatine products with mass numbers ranging from 208 to 205 is interpreted as evidence of processes in which energy deposited in the initial double charge exchange interaction is subsequently dissipated through neutron evaporation. The excitation functions for these reactions are seen to rise rapidly with decreasing incident pion energy with the maximum results for this study at 100 MeV. The astatine production cross secions measured for these positive pion irradiations of thick bismuth targets must be corrected for secondary processes, particularly the pion induced production of fast alpha particles which can contribute to the total cross sections through reactions like /sup 209/Bi(alpha,xn)/sup 213-x/At. The importance of these secondary contributions was studied through a series of negative pion irradiations of bismuth in which secondary pathways furnish the only means of producing astatine. The failure of evaporation calculations to reproduce the astatine product mass yields observed in these secondary studies suggests that direct mechanisms for energetic complex particle formation are quite important. Values for the alpha decay branches of /sup 207/At, /sup 208/At, and /sup 209/At were determined through a study of the electron capture and alpha decay characteristics of chemically purified astatine fractions.

• Research Organization: Carnegie-Mellon Univ., Pittsburgh, PA (USA)
• OSTI ID: 6085628
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA DECAY
ALPHA DECAY RADIOISOTOPES
ASTATINE 205
ASTATINE 206
ASTATINE 207
ASTATINE 208
ASTATINE 209
ASTATINE ISOTOPES
BARYONS
BETA DECAY RADIOISOTOPES
BISMUTH 209 TARGET
BOSONS
CHARGE-EXCHANGE REACTIONS
CHARGED-PARTICLE REACTIONS
CHEMICAL PREPARATION
CROSS SECTIONS
DECAY
DIRECT REACTIONS
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRON REACTIONS
HADRONS
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
ISOTOPES
KNOCK-OUT REACTIONS
MESON REACTIONS
MESONS
MEV RANGE
MEV RANGE 100-1000
MINUTES LIVING RADIOISOTOPES
NEUTRONS
NUCLEAR REACTIONS
NUCLEI
NUCLEONS
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
PION PLUS REACTIONS
PION REACTIONS
PIONS
PIONS MINUS
PSEUDOSCALAR MESONS
RADIOISOTOPES
SYNTHESIS
TARGETS