Proposal of measurements of M1 strengths in giant dipole resonance energy region

原子核中的M1跃迁在核物理和核天体物理学中引起了越来越多的关注。1957年，Agodi预测，在（gamma, n）反应中，100%线极化的偶极激发伽马射线束的中子角分布应该是各向异性的，并且在极性角为90度时，用a + b cos（phi）的简单函数来普遍描述，其中phi为方面角。然而，半个多世纪以来，这一预测还没有得到实验证实。我们利用线性偏振激光康普顿散射伽马射线在sprrioi -8的NewSUBARU上实验验证了Au-197， I-127，天然Cu， Fe-56目标的（gamma, n）反应中的角分布。通过改变入射激光线偏振面的角度，测量了中子的角分布。中子角分布很好地描述了Agodi预测的函数。

The M1 transitions in nuclei have attracted increasing attention in nuclear physics and nuclear astrophysics. In 1957, Agodi predicted that the neutron angular distribution in (gamma, n) reactions with a 100% linearly polarized gamma-ray beam for dipole excitation should be anisotropic and universally described by the simple function of a + b cos(phi) at polar angle of 90 degree, where phi is the azimuthal angle. However, this prediction has not been experimentally confirmed over half a century. We have verified experimentally this angular distribution in the (gamma, n) reaction for Au-197, I-127, natural Cu, Fe-56 targets using linearly polarized laser Compton scattering gamma-rays at NewSUBARU in SPrioing-8. Neutron angular distributions were measured by changing the angle of linear polarization plane of the incident laser. The neutron angular distributions are well described as the function predicted by Agodi.