搜索

x
中国物理学会期刊

基于激光悬浮的单颗微米粒子/纳米团簇的散射强度分布测量

CSTR: 32037.14.aps.72.20230499

Measurement of scattering intensity distribution of single microparticles/nanoclusters based on laser levitation

CSTR: 32037.14.aps.72.20230499
PDF
HTML
导出引用
  • 为了探索微/纳米粒子的散射特性, 提出采用贝塞尔光束悬浮和散射测量耦合的方法搭建悬浮散射测试系统装置, 对单颗微米粒子/纳米团簇的散射强度分布进行精确测量. 首先利用两束反向传输的贝塞尔光束对多种类型和尺寸的粒子/团簇进行悬浮, 判定粒子的悬浮稳定性; 然后对悬浮粒子以9.2'' 的角分辨率在平面2π角度内的散射强度分布进行测量. 模拟计算了激光作用下粒子的受力以及不同参数粒子的散射强度分布, 并与实验结果进行对比, 深入地分析了环境因素对散射测试系统不确定度的干扰程度, 详细讨论了悬浮不稳定性对散射测量结果的影响. 研究结果表明, 反向传输的贝塞尔光束可对金属镁、铝和石墨等粒子/团簇进行稳定悬浮, 其相对不稳定度小于0.15, 悬浮过程中光泳力起主导作用; 单颗微米粒子/纳米团簇的散射强度分布符合Mie粒子散射特征, 折射率虚部大的粒子具有更强的前向散射特性, 粒子尺寸参数越大, 则前向散射作用越强. 单颗微粒散射强度分布的精确测量证实了悬浮散射测试系统的通用性和可靠性, 为深入认识物质散射特性提供了一种新的研究手段.

     

    The scattering measurement of particulates in gaseous medium is helpful in understanding light transmission, laser detection, combustion radiation and atmospheric environment. In order to explore the scattering characteristics of micron-/nano-sized particles, this paper proposes a method of accurately measuring the scattering intensity distribution of a single micron-sized particles/nanoclusters by combining laser levitation and scattering measurement. An experimental apparatus is first built based on the counter-propagated bi-Bessel beams levitation system and scattering test system. The microparticles/nanoclusters of various matters and sizes are then levitated and their stabilities are evaluated. Finally, the scattering intensity distribution of levitated particles within 2π scattering angle is accurately measured with an angular resolution of 9.2″. The forces acting on particles under laser irradiation and the scattering intensity distribution of different particle parameters are simulated and calculated, and compared with experimental results. The influence of noise on the uncertainty of the scattering measurement system is analyzed in depth, including background light, laser beam, and reflected light from the walls. The results show that the signal-to-noise ratio of scattering measurement for metallic magnesium and aluminum, whether single particles or clusters, are both greater than 20 dB and their maximum values are both 94.6 dB in a range of 2π angle. For graphite nanoclusters, the signal-to-noise ratio in the backscattering direction is relatively poor. The influence of levitation instability on the scattering measurement results is estimated in detail, verifying that the influence of levitation instability in the test system on the scattering measurement is ignorable. Metallic magnesium, aluminum, and graphite particles can be stably levitated by the counter-propagated bi-Bessel beams, with a relative instability of less than 0.15. During the levitation, the photophoretic force plays a dominant role. The scattering intensity distribution of a single micron-sized particles and nanoclusters both conform to the scattering characteristics of Mie particles. Microparticles with large refractive index imaginary parts have stronger forward scattering characteristics. The larger the particle size parameter, the stronger the forward scattering effect becomes. The accurate measurement of the scattering intensity distribution of a single microparticles confirms the versatility and reliability of the levitation scattering test system, providing a new research method for in-depth understanding of the scattering characteristics of substances.

     

    目录

    /

    返回文章
    返回