Threshold states in 26Al : (I). Experimental investigations

Abstract

States in 26Al near the 25Mg + p threshold have been investigated using the 25Mg( 3He, d) 26Al reaction in order to locate levels which may serve as s-wave 25Mg + p resonances in the energy region characteristic of stellar hydrogen burning. One such state, with J π = (2, 3) +, has been observed at an excitation energy E x = 6343 keV, corresponding to a proton resonant energy of E c.m. = 37.2 keV. Studies on the 25Mg(d, p) 26Mg reaction indicate that the 6125 keV state in 26Mg is the isobaric analog to this 26Al state, and a spin-parity J π = 3 + is deduced for the 6125 keV state in 26Mg, through measurements of the 26Mg(α, α') 26Mg reaction. The γ-ray branching ratios for the 6343 keV state in 26Al have been measured using the 27Al( 3He, αγ) 26Al reaction, and it has been established that the decay of this state ultimately populates the ground state 57 % of the time. Similarly, the decay of the 6400 keV state in 26Al, studied via the 24Mg( 3He, p, γ) 26Al reaction, has been found to populate the ground state approximately 80% of the time.