【作者】 刘云；

【导师】 段传喜；

【作者基本信息】 华中师范大学 ， 物理学， 2023， 硕士

【摘要】 六氟化硫（SF₆）是一种长寿命的温室气体,其红外吸收光谱对模拟大气辐射平衡非常重要。SF₆也是研究激光分离同位素原理和技术的典型体系之一。由于SF₆分子较重,其室温下的红外光谱非常密集,给SF₆分子谱线的标识带来很大困难。本文利用超声射流冷却和像散型多程吸收池技术,测量了SF₆分子的高分辨红外激光吸收光谱,通过分析得出了超声分子束的物理特征。结果如下:我们测量了SF₆在v₃基频带945.9～948.8 cm^-1范围内与载气Ar在四种不同分压配比下（SF₆:Ar=10%:1,5%:1,1%:1,0.2%:1）的振转谱带。使用PGOPHER程序对吸收谱线进行拟合分析,估算得到了四种不同条件下分子束的转动温度T_rot。根据转动温度T_rot对超声分子束的马赫数M、轴向速度v、局部压强P等进行了计算。结果显示:分子束的转动温度T_rot和局部压强P随着SF₆浓度的降低而降低;分子束的马赫数M和轴向速度v随着SF₆浓度的降低而增大。当气体配比改为SF₆:Ar:He=0.12%:1%:1时,实现更低的转动温度T_rot=1.0 K,并在该条件下检测到SF₆-Ar复合物的平行谱带和垂直谱带,带头分别位于946.978 cm^-1、947.392 cm^-1。同时,使用圆孔型喷嘴对分子束进行喷射时,发现谱线的P支或R支中的每条谱线都有双峰结构。分析了产生这种双峰结构的可能原因,并确定了不同实验条件下的多普勒分裂。更多还原

【Abstract】 Sulfur hexafluoride（SF₆）is a greenhouse gas of very long lifetime.Its infrared absorption spectra are very important in modeling the atmospheric radiation balances.SF₆is also a prototypical system for studying the principles and techniques of laser isotope separation using powerful infrared lasers.As a very heavy molecule,the infrared spectra of SF₆ at room temperature are very dense,which poses a great challenge to assign and analyze them.In this work,an astigmatic multi-pass absorption cell and distributed feed-back quantum cascade lasers（QCLs）are used to measure the high-resolution infrared absorption spectra of SF₆,and the physical characteristics of supersonic molecular beam are analyzed.The results are as follows:The rovibrational absorption spectra of SF₆ of the v₃ fundamental band in the spectral range of 945.9～948.8 cm^-1 have been measured in a supersonic beam at four different mixing ratios of partial pressures（SF₆:Ar=10%:1,5%:1,1%:1,0.2%:1）.The rotational temperature T_rot of the molecular jet is estimated by comparing the simulated and observed spectrum using the PGOPHER program.Then the Mach number M,axial velocity v,local pressure P of the supersonic molecular beam are calculated according to the rotational temperature T_rot.The results show that the rotational temperature T_rot and local pressure P decrease with decreasing concentration,while the Mach number M and the axial velocity v increase with decreasing concentration.When the mixing ratio is changed to SF₆:Ar:He=0.12%:1%:1,a rotational temperature of T_rot=1.0 K is achieved and the parallel and perpendicular bands for SF₆-Ar complex is observed at 946.978 cm^-1,947.392 cm^-1,respectively.A double peak structure for each line in the P or R-branch is found when a pin-hole nozzle is used for supersonic expansion.The possible reasons for this double peak structure are analyzed and the Doppler splitting under different experiment conditions are determined.更多还原