First Evidence For Spin-Flip M1 Strength In Ar-40

The Ar-40(gamma ->,gamma(')) photon scattering reaction was used to search for spin-flip M1 strength in Ar-40. The nearly monochromatic, linearly polarized photon beam of HI gamma S, in an energy region from 7.7 to 11 MeV, was employed in this study. 28 dipole excitations were observed. The azimuthal intensity asymmetry indicated that all of these states were E1 except for the state at E-x=9.757 MeV. Shell-model calculations were used to interpret this state as one fragment of the spin-flip M1 strength in Ar-40.