Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005phdt........12d&link_type=abstract
Ph.D dissertation, 2005. 126 pages; United States -- Indiana: University of Notre Dame; 2005. Publication Number: AAT 3171615.
Astronomy and Astrophysics
Astrophysics
Lifetime Measurements, Excited States, Neon-19, Doppler Shift Attenuation, Novae, X-Ray Bursts, Branching Ratios
Scientific paper
In novae, x-ray bursts and some supernovae, the 15 O(a,g) 19 Ne reaction is a potential breakout path from the hot-CNO cycle and into the rp-process. The dominance of this reaction depends on the decay properties of the levels in 19 Ne above the a threshold. The 4.033 MeV state in 19 Ne, with its low spin (3/ 2 + ), is thought to be the main contributor to the reaction rate. The astrophysical rate of the 15 O(a,g) 19 Ne reaction can be calculated using the branching ratios and radiative widths or level lifetimes of states in 19 Ne.
Three experiments were done at the University of Notre Dame's Nuclear Structure Laboratory from 1999-2002 using the Doppler shift attention method (DSAM) to measure the lifetime of the 4.03 MeV state in 19 Ne via the 3 He( 17 O,n) 19 Ne and 19 F( 3 He,t) 19 Ne reactions. Two independent measurements of the lifetime were made placing a limit of 14 fs < t < 24 fs on the lifetime and therefore a limit on the g width of 27 meV < G g < 47 meV. These values agree with currently accepted values for the lifetime and support the belief that the 15 O (a,g) 19 Ne reaction is not a probable breakout path from the HCNO cycle into the rp-process in novae, but will have a greater impact on breakout in x-ray bursts.
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