摘要
与平面波相比,携带轨道角动量的涡旋γ光在垂直于传播方向上具有横向结构,其激发原子核跃迁过程与原子核相对光束中心的位置密切相关。本研究考虑了涡旋γ光束与具有高斯空间分布的微观核靶相互作用的过程,发现在巨共振能区,当高斯分布微观核靶与涡旋光束轴重合时,对于宽度小于入射光子波长的靶,涡旋γ光对吸收截面的抑制效果开始显现,随靶宽度的增大,同一多极性L的跃迁下涡旋γ光的吸收截面是平面波结果的1/cosθ_(k),θ_(k)为涡旋γ光的极化角;当靶与涡旋光束轴不重合时,若核靶分布宽度w小于光的横向尺寸,能观察到光吸收截面受涡旋γ光横向结构的影响,有明显的涡旋效应。因此通过涡旋γ光能实现对微观核靶的巨多极共振进行调控,能实现核靶对光束中不同角动量光子的选择性吸收,以上研究结果将为深入理解涡旋γ光子与原子核的相互作用和调控研究提供理论指导和参数支撑。
In the frontier field of nuclear physics,the interaction between vortexγphotons and nucleus has emerged as a captivating research direction,particularly due to the unique orbital angular momentum(OAM)carried by vortex photons.Unlike conventional plane-wave photons,vortexγphotons exhibit distinct concentric ring transverse intensity distributions and helical phase structure,leading to fundamentally different interaction mechanisms with nuclear systems.When a nucleus is aligned along the incident axis of a vortexγphoton,the photon’s OAM significantly changes nuclear transition selection rules,enabling selective excitation and extraction of specific multipole giant resonances phenomena typically constrained by dipole-dominated selection rules in plane-wave interactions.A critical parameter governing this interaction is the impact parameter b,defined as the transverse distance between the vortexγphoton’s incident axis and the nucleus.Compared to plane-wave photons,the annular intensity profile of vortex photons results in a strong dependence of photon absorption cross-sections on b.This necessitates a systematic investigation of how target spatial distributions modulate cross-sections and transition rules during vortex-nucleus interactions.In this study,the interaction of vortexγbeams with mesoscopic nuclear targets characterized by Gaussian spatial distributions was theoretically analyzed.Our findings reveal distinct mechanisms in the giant resonance energy region.When the mesoscopic nucleus target coincides with the vortex beam axis,for the target whose width is smaller than the wavelength of the incident photon,the absorption cross sections of the vortexγphoton begin to appear a suppression effect relative to plane-wave predictions.As the target width increases,the suppression diminishes,and the absorption cross-section of vortexγphotons at the same multipolar L transition is 1/cos θ_(k) as large as the plane-wave result and θ_(k) is the polarization angle of the vortexγphoton.When the target and the vortexγbeam axis do not coincide,if the width of the nucleus target distribution w is smaller than the transverse size of the photon,it can be observed that the photoabsorption cross section is affected by the transverse structure of the vortexγphoton,and there is an obvious vortex effect.Similar conclusions can be drawn for transitions with higher multipolarity L.Therefore,through the vortexγphoton,we can realize the regulation of the giant multipole resonances of the mesoscopic nucleus target and can recognize the selective absorption of the nucleus target to different angular momentum photons in the beam.The above results will provide theoretical guidance and parameter support for the in-depth understanding of the interaction between the vortexγphotons and the nucleus and the regulation study.
作者
张婉玉
卢知为
吕冲
牛一斐
张英逊
颜学庆
栗建兴
郭冰
ZHANG Wanyu;LU Zhiwei;LYU Chong;NIU Yifei;ZHANG Yingxun;YAN Xueqing;LI Jianxing;GUO Bing(Department of Nuclear Physics,China Institute of Atomic Energy,Beijing 102413,China;School of Physics,Xi’an Jiaotong University,Xi’an 710049,China;School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China;State Key Laboratory of Nuclear Physics and Technology,Peking University,Beijing 100871,China)
出处
《原子能科学技术》
北大核心
2025年第12期2593-2601,共9页
Atomic Energy Science and Technology
基金
国家科技部重点研发计划青年科学家项目(2024YFA1612700)
国家自然科学基金杰出青年项目(12125509)
核技术研发项目和重点项目(HJSYF2024(01),U2267204)
财政部稳定支持经费项目(18BJ010261224900)
中核集团“青年英才”菁英人才项目(FY222506000201)。
关键词
涡旋光
轨道角动量
巨共振
vortex photons
orbital angular momentum
giant resonances
