激波管壁AlO自由基B^2Σ^+-X^2Σ^+和C^2Π_r-X^2Σ^+带系辐射光谱的研究

Investigation on Spectrum of B^2Σ^+-X^2Σ^+ and C^2Π_r-X^2Σ^+ Bands of AlO Radical in Shock Tube

爆轰驱动过程中产生的高温高压气流对铝质膜片、激波管壁产生烧蚀和冲刷作用,以致激波管壁、端盖上附有氧化铝等杂质,而高温下AlO自由基在气体分子的高速碰撞下被激发并产生强烈的辐射,从而干扰了高温气体辐射光谱的分析。用爆轰驱动加热技术将空气加热到4 000~7 000 K,利用多通道光学分析仪对AlO自由基辐射光谱进行分析,实验发现在460~530 nm波长范围内有多支辐射非常强烈的AlO自由基B2Σ+-X2Σ+(T00=20 689 cm-1)带系辐射谱带,且每支谱带都由多个带头组成,带头间隔约为2 nm,带头处于高频位置并向低频方向伸延。通过实验与理论计算相结合,重点分析了AlO自由基B2Σ+-X2Σ+带系辐射光谱的结构特征。AlO自由基C2Πr-X2Σ+(T00=33 047 cm-1)带系辐射光谱处于270~335 nm波长范围内,其辐射强度相对于B2Σ+-X2Σ+带系较弱,并且与OH基A2Σ+-X2Π(T00=32 682 cm-1)带系辐射光谱互相干扰而难以分辨,对该波段高温空气的辐射光谱分析产生不利的影响。

There are some impurities such as aluminum dioxide adhering on the shock tube wall due to the ablating and heating of the aluminum diaphragm by high temperature gas. Under high temperature, the collision of AlO radicals with the gaseous molecules leads to transition of the electronic states and production of strong radiation, which disturb the analysis of radiation spectrum of heated gases in shock tube. In the authors＇ experiments, the air in the test section with adhering aluminum dioxide was heated to some 4 000-7000 K, the spectrum of AlO radical was obvious in the range of 460-530 nm, which corresponds to B^2∑＋-X^2∑＋ （T00 =20 689 cm^-1 band. There were several band heads for this band, the interval of neighbor heads was some 2 nm, and all the band heads were with the shortest wavelength. The characteristics of B^2∑＋-X^2∑＋ band were explored in experiment and by theory. In addition, the spectrum of C2Ⅱr-X^2∑＋（T00 = 33 047 cm^-1 ） band was also investigated. The corresponding strength was lower than that of B^2∑＋-X^2∑＋ band, and the wavelength range of this band was some 270-335 nm where the radiation of A^2∑＋-X^2Ⅱ（T00 =32 682 cm^-1） band of OH radical also existed. This occurrence of the two bands in the same wavelength range is disadvantageous for the spectrum analysis.