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The reduced-alpha-width of the lowest 1¯ state of ^(16)O

Citation

Dyer, Peggy Lynn (1973) The reduced-alpha-width of the lowest 1¯ state of ^(16)O. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:10292015-105646231

Abstract

Cross sections for the reaction 12C(α,γ)16O have been measured for a range of center-of-mass alpha particle energies extending from 1.72 MeV to 2.94 MeV. Two 8"x5" NaI (Tℓ) crystals were used to detect gamma rays; time-of-flight technique was employed to suppress cosmic ray background and background due to neutrons arising mainly from the 13C(α,n)16O reaction. Angular distributions were measured at center-of-mass alpha energies of 2.18, 2.42, 2.56 and 2.83 MeV. Upper limits were placed on the amount of radiation cascading through the 6.92 or 7.12-MeV states in 16O. By means of theoretical fits to the measured electric dipole component of the total cross section, in which interference between the 1¯ states in 16O at 7.12 MeV and at 9.60 MeV is taken into account, it is possible to extract the dimensionless, reduced-alpha-width of the 7.12-MeV state in 16O. A three-level R-matrix parameterization of the data yields the width Θα,F2 = 0.14+0.10-0.08. A "hybrid" R-matrix-optical-model parameterization yields Θα,F2 = 0.11+0.11-0.07. This quantity is of crucial importance in determining the abundances of 12C and 16O at the end of helium burning in stars.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Barnes, Charles A.
Thesis Committee:
  • Unknown, Unknown
Defense Date:15 December 1972
Funders:
Funding AgencyGrant Number
NASA TraineeshipUNSPECIFIED
NSFGP-28027
Record Number:CaltechTHESIS:10292015-105646231
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:10292015-105646231
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9259
Collection:CaltechTHESIS
Deposited By: Bianca Rios
Deposited On:29 Oct 2015 23:18
Last Modified:29 Oct 2015 23:18

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