【作者】 张伟；

【导师】 袁萍； 蒋军；

【作者基本信息】 西北师范大学 ， 原子与分子物理， 2019， 硕士

【摘要】 闪电等离子体的放电特征和物理机制等方面的研究内容是目前备受关注的课题之一,温度是反映闪电等离子体放电特性的重要参数之一。迄今为止,关于闪电等离子体的研究通常是在光学观测的基础上进行的。我们小组的成员使用具有高时间分辨率的无狭缝摄谱仪,在青海高原地区拍摄获取了雷电光谱数据,本工作以这些光谱作为研究对象,结合闪电等离子体通道的发光机制,首次针对闪电等离子体建立了碰撞辐射模型。氮离子(NII)谱线500.52和567.96nm是闪电光谱中反映放电电流强度的强谱线之一,我们计算并且获得了这两条特征谱线不同温度下的相对总辐射强度,进而获得了这两条特征强谱线的相对总辐射强度的比值与温度之间的关系,最后将这个关系应用在实验光谱中,得到了闪电等离子体的温度。主要内容依次如下:首先,根据多组态Dirac-Fock方法理论,基于Flexible Atomic Code程序,计算了氮离子(NII)的相关能级、跃迁几率、碰撞截面、碰撞强度及电子碰撞激发速率系数等原子参数。其次,根据原子或离子的辐射谱线强度分别与基态到激发态的电子碰撞激发速率系数以及高激发态到低激发态的跃迁几率呈正比这一理论基础,建立了碰撞辐射模型理论。进一步计算了闪电光谱图中表现比较明显的氮离子的特征强谱线567.96nm和500.52nm及与其相关的各个跃迁的相对辐射强度,然后得到了这两条强谱线在不同温度下的相对总辐射强度及其比值,为进一步将其应用在实验光谱中奠定了基础。最后,通过分析六个闪电的回击过程的实验光谱,计算了对应的六个闪电等离子体通道的发射光谱中的特征强谱线567.96nm和500.52nm的相对总光谱强度,结合碰撞辐射模型获得的相对总辐射强度的比值,得到了这六个闪电等离子通道的温度。此外,利用多谱线法对这六个闪电等离子体的通道温度进行了估算,通过与上述理论计算获得的温度进行比对,可以看出两种方法所获得的结果的差异在2500K以内。更多还原

【Abstract】 The research on the discharge characteristics and physical mechanism of lightning plasma is one of the most concerned topics at present.Temperature is one of the important parameters which could reflect the discharge characteristics of lightning plasma.So far,lightning plasma has usually been studied on the basis of optical observations.Members of our team obtained lightning spectrum data in the Qinghai plateau by using a slitless spectrogragh with high time resolution.By using these spectra as the research object,the collisional-radiative model was established by combining with the luminescence mechanism of lightning plasma channel for the first time.Nitrogen ion(NII)spectral lines 500.52 and 567.96 nm are one of the stronger spectral lines which can reflect the discharge current intensity in the lightning spectrum.We have calculated the total relative radiation intensity of these two characteristic spectral lines at different temperatures,and then have obtained the relationship between the ratio of the total relative radiation intensity of these two characteristic strong spectral lines and temperature.Finally,the relationship is applied to the experimental spectrum,and the temperature of lightning plasma have been obtained.The main contents are as follows:Firstly,according to the theory of multi-configuration Dirac-Fock method,the atomic parameters such as correlative energy levels,transition probabilities,collision cross sections,collision strengths and electron collision excitation rate coefficients of nitrogen ion(NII)have been calculated based on Flexible Atomic Code program.Secondly,collision radiation model is established according to the theoretical basis,where the intensity of the radiative spectral line of atoms or ions is proportional to the electron collision excitation rate coefficient from the ground state to the excited states and it is also proportional to the transition probability from the high excitation state to the low excitation state.The characteristic spectral lines 567.96 and 500.52 nm of nitrogen ion is stronger in lightning spectra,and the relative radiative intensity of each transition associated with them have been calculated further.The ratio of the relative total radiative intensity of these two strong spectral lines have been obtained at different temperatures.It has laid a foundation for further application in the experimental spectrum.Finally,by analyzing the experimental spectra of six lightnings,the total relative spectral intensities of the characteristic strong spectral lines 567.96 nm and 500.52 nm of them have been obtained,the temperature of these six lightning plasma channels have been also obtained by combining the ratio of the relative total radiation intensity obtained by the collisional-radiative model.In addition,the channel temperature of the six lightning plasmas is estimated by using the multi-spectral method.By comparing with the temperature obtained based on theoretical calculation,it can be found that the differences of the results obtained by two methods were within 2500 K.更多还原