This work uses in situ narrowband quantum cascade laser (QCL) absorption spectroscopy to study the effect of N2 on the time evolution of gas temperature, rotational temperature and the vibrational temperatures of CO2 and CO in a pulsed glow discharge. Three colinear QCLs are used to scan three regions of about 1 cm-1 between 2179.20 and 2253.51 cm-1, including (v 1,v2-l 2,v 3)\to (v 1,v 2-l2,v3+1) C O 2 transitions up to the asymmetric stretch level v 3 = 6, as well as (v CO) → (v CO + 1) CO transitions up to v CO = 1. A fitting routine is used to extract temperatures from the measured absorption spectra. The time resolved measurements are performed in CO2, admixed with up to 90% N2, with the plasma operated with a 5-10 ms on-off cycle, a discharge current of 50 mA and a pressure of around 6.7 mbar. The time evolution of the gas temperature has been measured and agrees well with the time evolution of the rotational temperature. The asymmetric stretch vibrational temperature T 3 of CO2 reaches a maximum of 1060 K at 0.7 ms for pure CO2, while T 3 goes up to 2250 K for a N2 content of 90% and stays constant until the plasma is switched off. Both T 3 and the vibrational temperature of CO T CO show a clear non-equilibrium with respect to the rotational temperature T rot. Both do not equilibrate with the rotational temperature T rot between consecutive plasma cycles for a N2 content above 70%, although T 3 and T CO always equilibrate with each other in the afterglow. The symmetric stretch and bending mode temperature T 12 is elevated more with respect to the rotational temperature for increasing N2 content, while the maximum of the rotational temperature decreases for increasing N2 admixtures, which might be attributed to the energy stored in the vibrational modes of N2, CO2 and CO. Additionally, an indication of an increase in the total pressure during the plasma on-time due to heating and a subsequent decrease in the afterglow due to cooling was found for a pure CO2 plasma.

中文翻译：

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使用量子级联激光吸收光谱测量脉冲 CO ₂ -N ₂辉光放电中的温度演变

这项工作使用原位窄带量子级联激光 (QCL) 吸收光谱来研究 N2 对脉冲辉光放电中气体温度、旋转温度以及 CO2 和 CO 振动温度的时间演变的影响。三个共线 QCL 用于扫描 2179.20 和 2253.51 cm-1 之间大约 1 cm-1 的三个区域，包括 (v 1,v2-l 2,v 3)\to (v 1,v 2-l2,v3+1 ) CO 2 跃迁至不对称拉伸水平 v 3 = 6，以及 (v CO) → (v CO + 1) CO 跃迁至 v CO = 1。拟合例程用于从测量的吸收中提取温度光谱。时间分辨测量是在 CO2 中进行的，混合了高达 90% 的 N2，等离子体以 5-10 ms 的开关循环、50 mA 的放电电流和大约 6.7 mbar 的压力运行。已经测量了气体温度的时间演变并且与旋转温度的时间演变非常吻合。对于纯 CO2，CO2 的不对称拉伸振动温度 T 3 在 0.7 ms 时达到最大值 1060 K，而对于 N2 含量为 90% 的情况，T 3 上升到 2250 K，并且在等离子体关闭之前保持恒定。T 3 和CO T CO 的振动温度都显示出相对于旋转温度T rot 的明显非平衡。对于高于 70% 的 N2 含量，两者都不会与连续等离子体循环之间的旋转温度 T rot 平衡，尽管 T 3 和 T CO 总是在余辉中彼此平衡。对称拉伸和弯曲模式温度 T 12 相对于旋转温度升高更多，以增加 N2 含量，