Title: Simultaneous measurement of mass and rotation of trapped absorbing particles in air Show Chinese title

Title: 空气中被捕获吸收粒子的质量和旋转的同步测量

Abstract: We trap absorbing micro-particles in air by photophoretic forces generated using a single loosely focused Gaussian trapping beam. We measure a component of the radial Brownian motion of a trapped particle cluster and determine the power spectral density, mean squared displacement, and normalized position and velocity autocorrelation functions in order to characterize the photophoretic body force in a quantitative fashion for the first time. The trapped particles also undergo spontaneous rotation due to the action of this force. This is evident from the spectral density that displays clear peaks at the rotation and the particles' inertial resonance frequencies. We fit the spectral density to the well-known analytical function derived from the Langevin equation, measure the resonance and rotation frequencies and determine values for particle mass that we verify at different trapping laser powers with reasonable accuracy. Show Chinese abstract

Abstract: 我们通过使用单个松散聚焦的高斯捕获光束产生的光泳力，在空气中捕获吸收性微粒子。 我们测量被捕获粒子团的径向布朗运动的一个分量，并确定功率谱密度、均方位移以及归一化的位移和速度自相关函数，以首次定量表征光泳体力。 由于该力的作用，被捕获的粒子也会发生自发旋转。 从显示旋转频率和粒子惯性共振频率处明显峰的谱密度可以明显看出这一点。 我们将谱密度拟合到由朗之万方程得出的著名解析函数，测量共振和旋转频率，并确定粒子质量的值，且在不同捕获激光功率下以合理的准确性进行了验证。