In this work, we present a theoretical study of the angular dynamics of small nanoparticles induced by fast non-vortex electron beams. General expressions for the torque and the angular momentum transferred from an electron to an arbitrary—but small—nanoparticle are obtained using a full-retarded classical electrodynamics approach, within the small particle limit. We applied this methodology to study a particular case of interest: the angular dynamics of spherical nanoparticles with homogeneous and isotropic electromagnetic responses. We analytically calculate the total angular momentum transferred from a swift electron to such nanoparticles, finding that it is electric in nature and it is always in a direction determined by the electron trajectory relative to the center of the nanoparticle. We realize that it is possible to represent the angular momentum transferred as the product of two functions: the extinction cross-section of the nanoparticle and a function that only contains information about the swift electron. We present numerical results for the total angular momentum transferred from a swift electron to an aluminum and a gold nanoparticle. We also present an analysis of the temporal behavior of the torque and the electric dipole moment induced within the nanoparticle by the swift electron. We compare the angular momentum transfer calculated in this work with a previously reported case of vortex beams, finding that, for both aluminum and gold nanoparticles, our results are two orders of magnitude smaller. Finally, we consider a particular case of a frictionless gold spherical nanoparticle of radius $a=5\mathrm{nm}$, obtaining that it can spin with an angular frequency up to $29.3\mathrm{Hz}$.

在这项工作中，我们提出了由快速非涡旋电子束诱导的小纳米粒子的角动力学的理论研究。从电子转移到任意但很小的纳米粒子的转矩和角动量的一般表达式是使用全延迟的经典电动力学方法在小粒子范围内获得的。我们应用这种方法研究了一个特定的案例：具有均质和各向同性电磁响应的球形纳米粒子的角动力学。我们分析性地计算了从快速电子转移到此类纳米颗粒的总角动量，发现它本质上是电的，并且始终处于由电子轨迹相对于纳米颗粒中心确定的方向。我们意识到，可以将传递的角动量表示为两个函数的乘积：纳米粒子的消光截面和仅包含有关快速电子信息的函数。我们提出了从快速电子转移到铝和金纳米粒子的总角动量的数值结果。我们还提出了由快速电子在纳米粒子内感应出的转矩和电偶极矩的时间行为的分析。我们将这项工作中计算的角动量转移与先前报道的涡旋束情况进行了比较，发现对于铝和金纳米颗粒，我们的结果都小两个数量级。最后，我们考虑一个无摩擦的球形金纳米颗粒的特殊情况$\mathrm{一种}=5\mathrm{纳米}$，获得它可以以高达 $29。3\mathrm{赫兹}$。