Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications

Details Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications

Jan 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........89g&link_type=abstract

Thesis (PH.D.)--UNIVERSITY OF NOTRE DAME, 1992.Source: Dissertation Abstracts International, Volume: 53-06, Section: B, page: 29

Astronomy and Astrophysics

Astrophysics

3

Oxygen-18, Neon-22, Alpha Capture

Scientific paper

The ^{22}Ne( alpha,n)^{25} Mg reaction is considered as a major neutron source for the s-process in Helium burning zones of Red Giant Stars. Its reaction rate and that of its feeding reaction ^{18}O(alpha, gamma)^{22}Ne bear large uncertainties in the important temperature range T _9 = 0.1-0.4 (10^9K). The ^{18}O( ^6Li,d)^{22}Ne and ^{22}Ne(^6 Li,d)^{26}Mg alpha-transfer reactions at E_ {rm Li} = 32 MeV have been used to search for natural parity states just above the alpha-threshold. Angular distribution measurements and DWBA-analysis for 12 levels in ^{22 }Ne in the range of E_{ rm x} = 8.6-11.3 MeV resulted in spin assignments and the extraction of alpha -spectroscopic factors. Similarly, six levels in ^{26}Mg between E_ {rm x} = 9.4-12.05 MeV have been analyzed, level spins are proposed and alpha -spectroscopic factors determined. Of astrophysical importance is the finding of one new level and the confirmation of three previously observed levels just above the alpha-threshold in ^{22 }Ne. The astrophysical implications of two strongly populated levels in ^{26} Mg above the alpha-threshold but below the n-threshold will also be discussed. The ^{18}O( alpha,gamma)^{22}Ne reaction has been investigated at E_alpha = 340-800 keV to measure directly the newly found levels in ^{22}Ne as resonances in ^{18}O(alpha, gamma)^{22}Ne. The angular distribution of the gamma-decay of the lowest three known resonances have also been measured to determine their resonance spins and alpha -spectroscopic factors. The combined results of alpha-capture and alpha -transfer measurements on ^{18 }O are used to determine the stellar reaction rate for ^{18}O( alpha,gamma)^{22}Ne. For the temperature range T_9 = 0.1 -0.3 we have found an increase in the production of ^{22}Ne by a factor of about 100, relative to previous estimates. The ^{22}Ne( alpha,n)^{25} Mg reaction has been investigated at E_ alpha = 600-925 keV. One resonance at E _alpha = 828 keV has been found and its strength has been determined. The combination of this and the results from the ^{22} Ne(^6Li,d)^ {26}Mg measurements allowed to determine the reaction rates of the ^{22} Ne(alpha,gamma)^{26 }Mg and ^{22}Ne( alpha,n)^{25} Mg reaction for T_9~ 0.2 -0.6.

Affiliated with

Also associated with

No associations

Rating

Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Study of Alpha-Capture and Alpha-Transfer Reactions on OXYGEN-18 and NEON-22 and Astrophysical Implications will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-940134