在室温条件下的小型云室中,研究了不同参数对飞秒激光诱导较大尺寸气溶胶生成的影响。实验结果表明,在亚饱和条件下,随着环境相对湿度的提高,不同尺寸气溶胶的数密度增大,尺寸分布以0.3~0.5 μm为主;当环境相对湿度达到近饱和条件时,较大尺寸(直径D≥0.7 μm)气溶胶的数密度显著增大,1.0~2.0 μm气溶胶与0.3~0.5 μm气溶胶的数密度可相比拟。此时,通过延长激光照射时间或者缩紧激光聚焦条件,不同尺寸气溶胶的数密度可同等程度地增大,尺寸分布规律基本不变。理论分析结果表明,环境相对湿度条件是制约飞秒激光诱导较大尺寸气溶胶生成的关键因素。

Under room temperature, the influences of different parameters on the formation of femtosecond laser-induced aerosols with relatively large size in a small cloud chamber are studied. The experimental results show that, under sub-saturated condition, the aerosol number density increases with the increase of relative humidity, and 0.3-0.5 μm aerosols are dominated. However, when the environmental relative humidity is near to be saturated, the number density of relative large-size aerosols (with their diameter D≥0.7 μm) is enhanced mostly, and at the end, the number density of 1.0-2.0 μm aerosols is comparable with that of 0.3-0.5 μm aerosols. When the laser irradiation duration and tightened focusing condition are prolonged under this near saturated condition, the number density of different size aerosols increases simultaneously at the same degree, and ultimately the corresponding size distribution does not change too much. Theoretical analysis results show that environmental relative humidity plays a key role for femtosecond laser-induced relative large-size aerosol formation.