The nucleosynthesis of sup 180 Ta

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5097164

Kellogg, S E

It has been proposed by Beer and Ward that the abundance of nature's rarest isotope, {sup 180}Ta, could be quantitatively accounted for in the standard stellar slow (s) and/or rapid (r) neutron-capture processes through the existence of small, previously unmeasured {beta}-branches which drain and feed the population of the t{sub {1/2}} = 5.5 hour isomer of {sup 180}Hf(BE81). We have conducted a series of experiments designed to measure these small {beta}-branches. We have: (1) measured the direct (isomer-to-isomer) 214-keV-endpoint {beta} branch from {sup 180}Hf{sup m} to {sup 180}Ta{sup m} to be f{sub {beta}} = 0.30 {plus minus} 0.07 {plus minus} 0.07% (KE87), (2) observed a new {gamma} ray in the decay of {sup 180}Hf{sup m} which indicated a small {beta}-branch of 0.023% to an excited state in {sup 180}Ta (KE85), (3) established a stringent limit of 0.023% on the fraction f{sub m} of {sup 180}Lu decays which populate {sup 180}Hf{sup m} (KE86), (4) sought to identify a possible high-spin, short-lived isomer of {sup 180}Lu, and established upper limits on its possible half-life (LE86), (5) established limits on the {sup 180}Ta{sup m} photodeexcitation cross-section via resonant and nonresonant processes (NO84a), and (6) calculated upper-limits on the life-time of {sup 180}Ta{sup m} in a stellar environment. Taken together, this body of work makes it unlikely that the Beer and Ward model can account for the observed solar-system abundance of {sup 180}Ta. Other possible production schemes are reviewed and directions for further research are suggested.

• Research Organization: Washington Univ., Seattle, WA (USA)
• OSTI ID: 5097164
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360106 -- Metals & Alloys-- Radiation Effects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
640100* -- Astrophysics & Cosmology
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DATA
ELECTRON CAPTURE RADIOISOTOPES
EMISSION
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HAFNIUM 180
HAFNIUM ISOTOPES
HOURS LIVING RADIOISOTOPES
INFORMATION
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MEASURING INSTRUMENTS
MEASURING METHODS
NEUTRON EMISSION
NUCLEI
NUCLEOSYNTHESIS
NUMERICAL DATA
ODD-ODD NUCLEI
RADIOISOTOPES
STABLE ISOTOPES
SYNTHESIS
TANTALUM 180
TANTALUM ISOTOPES