| 气体压强对纳秒激光诱导空气等离子体特性的影响 |
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| 引用本文： | 刘家合,鲁佳哲,雷俊杰,高勋,林景全.气体压强对纳秒激光诱导空气等离子体特性的影响[J].物理学报,2020(5):202-208. |
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| 作者姓名： | 刘家合 鲁佳哲 雷俊杰 高勋 林景全 |
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| 作者单位： | 长春理工大学理学院;西安应用光学研究所 |
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| 基金项目： | 国家自然科学基金(批准号:61575030);吉林省自然科学基金(批准号:20180101283JC);吉林省教育厅项目(批准号:JJKH20190539KJ);长春理工大学创新基金(批准号:XJJLG-2017-10)资助的课题~~ |
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| 摘 要： | 环境气体的压强对激光诱导等离子体特性有重要影响.基于发射光谱法开展了气体压强对纳秒激光诱导空气等离子体特性影响的研究,探讨了气体压强对空气等离子体发射光谱强度、电子温度和电子密度的影响.实验结果表明,在10-100 kPa空气压强条件下,空气等离子体发射光谱中的线状光谱和连续光谱依赖于气体压强变化,且原子谱线和离子谱线强度随气体压强的变化有明显差别.随着空气压强增大,激光击穿作用区域的空气密度增加,造成激光诱导击穿空气几率升高,从而等离子体辐射光谱强度增大.空气等离子体膨胀区域空气的约束作用,增加了等离子体内粒子间的碰撞几率以及能量交换几率,并且使离子-电子-原子的三体复合几率增加,因此造成原子谱线OⅠ777.2 nm与NⅠ821.6 nm谱线强度随着气体压强增大而增大,在80 kPa时谱线强度最高,随后谱线强度缓慢降低.而离子谱线N Ⅱ 500.5 nm谱线强度在40 kPa时达到最大值,气体压强大于40 kPa后,谱线强度随压强增加而逐渐降低.空气等离子体电子密度均随压强升高而增大,在80 kPa后增长速度变缓.等离子体电子温度在30 kPa时达到最大值,气体压强大于30 kPa后,等离子体电子温度逐渐降低.研究结果可为不同海拔高度的激光诱导空气等离子体特性的研究提供重要实验基础,为今后激光大气传输、大气组成分析提供重要的技术支持.
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| 关 键 词： | 纳秒激光 气体压强 空气等离子体 三体复合 |
Effect of ambient gas pressure on characteristics of air plasma induced by nanosecond laser |
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| Liu Jia-He,Lu Jia-Zhe,Lei Jun-Jie,Gao Xun,Lin Jing-Quan.Effect of ambient gas pressure on characteristics of air plasma induced by nanosecond laser[J].Acta Physica Sinica,2020(5):202-208. |
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| Authors: | Liu Jia-He Lu Jia-Zhe Lei Jun-Jie Gao Xun Lin Jing-Quan |
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| Affiliation: | (School of Science,Changchun University of Science and Technology,Changchun 130022,China;Xi’an Institute of Applied Optics,Xi’an 710065,China) |
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| Abstract: | The ambient gas pressure has an important influence on the laser induced plasma characteristics.The effects of gas pressure on the characteristics of air plasma induced by nanosecond laser are studied by using the optical emission spectroscopy,and the relationship between the gas pressure and the spectral intensity,and between electron temperature and electron density of air plasma are discussed.The air gas pressure in chamber is continuously changed in a range from 10 to 100 kPa by using a mechanical pump and measured by using a barometer.The ns laser energy in experiment is fixed at 100 mJ in the whole experiment.The digital delay trigger(Stanford DG535/645)is used to trigger the laser and ICCD synchronously,and the delay and gate time of ICCD are set to be 0 and 5μs,respectively.The experimental results show that air plasma emission spectrum consists of the line and continuous spectrum,and the spectral intensity of air plasma emission spectrum is dependent on gas pressure in a range from 10 to 100 kPa,and the evolution of atomic spectrum intensity with gas pressure is different from that of ion spectrum intensity.The air density in the region of laser breakdown increases with air pressure increasing,which leads the breakdown probability of air gas to increase,thus resulting in the air plasma spectral intensity increasing.Under the confinement action of the ambient air gas in the expanding region of air plasma,the collision probability and energy exchange probability among particles in the air plasma are both increased,and the trisomic recombination probability of ion-electron-atom is also increased.As a result,the atomic spectral intensity of OΙ777.2 nm and NΙ821.6 nm both increase with the air gas pressure increasing,and the spectral intensity is highest at 80 kPa,and then slowly decreases.But the spectral intensity of N II 500.5 nm reaches its maximum value at 40 kPa,and decreases as the pressure becomes greater than 40 kPa.The electron density of the air plasma increases with the air pressure increasing,and the growth rate becomes slow after 80 kPa.The electron temperature of the air plasma reaches a maximum value at 30 kPa.The plasma electron temperature gradually decreases as the pressure becomes greater than 30 kPa.The research results can provide an important experimental basis for studying the laser-induced air plasma characteristics at different altitudes,and also give important technical support for laser atmospheric transmission and atmospheric composition analysis in the future. |
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| Keywords: | nanosecond laser pressure air plasma three-body recombination |
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