Xia Yu, Xu Jinheng, Li Juan, Chen Bolei, Dai Yifan, Zare Richard N
Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, School of Environment and Health, Jianghan University, Wuhan 430056, P. R. China.
J Phys Chem A. 2024 Jul 18;128(28):5684-5690. doi: 10.1021/acs.jpca.4c02981. Epub 2024 Jul 5.
Water droplets are spraying into air using air as a nebulizing gas, and the droplets pass between two parallel metal plates with opposite charges. A high-speed camera records droplet trajectories in the uniform electric field, providing visual evidence for the Lenard effect, that is, smaller droplets are negatively charged whereas larger droplets are positively charged. By analyzing the velocities of the droplets between the metal plates, the charges on the droplets can be estimated. Some key observations include: (1) localized electric fields with intensities on the order of 10 V/m are generated, and charges are expected to jump (micro-lightening) between a positively charged larger droplet and the negatively charged smaller droplet as they separate; (2) the strength of the electric field is sufficiently powerful to ionize gases surrounding the droplets; and (3) observations in an open-air mass spectrometer reveal the presence of ions such as N, O, NO, and NO. These findings provide new insight into the origins of some atmospheric ions and have implications for understanding ionization processes in the atmosphere and chemical transformations in water droplets, advancing knowledge in the field of aerosol science and water microdroplet chemistry.
利用空气作为雾化气体将水滴喷入空气中，水滴在带有相反电荷的两个平行金属板之间穿过。高速摄像机记录均匀电场中水滴的轨迹，为莱纳德效应提供视觉证据，即较小的水滴带负电而较大的水滴带正电。通过分析金属板之间水滴的速度，可以估算水滴上的电荷。一些关键观察结果包括：（1）会产生强度约为10 V/m的局部电场，预计当带正电的较大水滴和带负电的较小水滴分离时，电荷会在它们之间跳跃（微闪电）；（2）电场强度足以使水滴周围的气体电离；（3）在露天质谱仪中的观察结果表明存在诸如N、O、NO和NO等离子。这些发现为一些大气离子的起源提供了新的见解，并对理解大气中的电离过程和水滴中的化学转化具有启示意义，推动了气溶胶科学和水微滴化学领域的知识发展。
