Photo-response of the N = Z nucleus ²⁴Mg

The electric E1 and magneticM1 dipole responses of the N = Z nucleus Mg-24 were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the 24Mg(gamma, gamma') reaction, were delivered by theELBEaccelerator of theHelmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one J(pi) = 1(-), four J(pi) = 1(+), and six J(pi) = 2(+) states in Mg-24 gamma De-excitation. rays were detected using the four high-purity germanium detectors of the gamma ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0MeV a total B( M1) up arrow= 2.7(3) mu(2)(N) is observed, but this N = Z nucleus exhibits only marginal E1 strength of less than Sigma B(E1)up arrow <= 0.61 x 10(-3) e(2) fm(2). The B(Pi 1, 1(i)(pi) -> 2(1)(+))/B(Pi 1, 1(i)(pi) -> (+)(gs)) branching ratios in combination with the expected results from the Alaga rules demonstrate that K is a good approximative quantum number for Mg-24. The use of the known rho(2)(E, 0(2)(+) -> 0(gs)(+)) strength and the measured B(M1, 1(+) -> 0(2)(+))/B( M1, 1(+) -> 0(gs)(+)) branching ratio of the 10.712 MeV 1(+) level allows, in a two-state mixing model, an extraction of the difference Delta beta(2)(2) between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV 0(2)(+) level.