| Recent observations of isotopic abundances in the atmospheres of M13 red giant branch stars show an anticorrelation between Al and 24Mg abundances. These correlations are thought to be the result of deep mixing of material from the surface of the star into regions where the temperature is high enough to allow proton captures to take place. Production of Al and destruction of 24Mg depend on the 24Mg( p, gamma)25Al reaction rate at stellar temperatures T9 ∼ 0.04 (where T9 denotes temperature in units of 109 K). However, the commonly used rate is too low to account for the observations within the present mixing models. There exists an uncertainty in the total width Gamma of the ER = 223-keV (Ex = 2485 keV) resonance in the 24Mg(p,gamma)25Al reaction which could lead to enhancements in the reaction rate up to a factor of 32 at T9 = 0.04. The main goal of this thesis is to accurately determine the properties of the ER = 223-keV resonance in order to improve the reaction rate estimate for 24Mg(p, gamma) 25Al.; Resonance strength ogamma-, gamma-ray branching ratios Gamma gamma/Gamma, and mean lifetimes tau were determined for the E R = 223- and 419-keV resonances in 24Mg(p, gamma) 25Al. These parameters allow for the determination of proton partial widths Gammap, gamma-ray partial widths Gamma gamma, and total widths Gamma necessary for the calculation of the resonant cross section at Ep < 500 keV. The rate for the 24Mg(p, gamma)25Al reaction for temperatures of T9 = 0.02 -- 2 was calculated. The reaction rate deviates from the previous estimates by 18% to 45%, and therefore, the total width of the ER = 223-keV resonance does not have a significant influence on the reaction rate.; In addition, branching ratios were determined for the 223-, 419-, 1616-, and 1654-keV resonances in 24Mg(p, gamma) 25Al, and for the 406-keV resonance in 27Al( p, gamma)28Si. Spectroscopic factors were determined from the proton partial widths for the states corresponding to the E R = 223- and 419-keV resonances. Resonance strength values were also determined for the 435-keV resonance in 25Mg(p, gamma) 26Al, the 336- and 454-keV resonances in 26Mg( p, gamma)27Al, and the 406keV resonance in 27Al(p, gamma)28Si. |
