CH分子束的强度与CH_4/He混合配比的关系及CH(A~2Δ)振转温度的计算

为了获得CH分子束及其相关特性,以氦气为载气,利用直流脉冲放电技术产生了CH分子束。实验记录了放电时间相对于脉冲分子束不同延时CH光谱信号强度的变化,放电相对延时为460μs左右获得最大的信号强度。研究了在保持CH4/He总气压3 atm和放电电压-4 kV不变的条件下CH分子束强度与不同配比的关系,建立了理论模型,对实验数据进行了理论拟合,拟合曲线与实验结果符合较好,配比为1%(甲烷与氦的气压比为1∶99)左右能够维持较稳定的放电现象和较强的放电强度而获得较强的CH自由基束流。在这一配比下对CH(A2Δ-X2Π)(0,0)带发射光谱进行探测和分析,获得CH(A2Δ)转动温度和振动温度分别为2455 K和4575 K,并估计此时每个脉冲中大约包含1013~1014个CH自由基。

Dependence of CH Molecular Beam Intensity on Ratio of CH4Buffering in Helium and Vibration and Rotation Temperatures Calculation of CH(A2Δ)

The CH molecular beam was generated by DC pulsed discharging methane seeded in helium in the supersonic expansion to study the generation and features of CH molecular beams. The variation of the CH spectral intensity with the different time delay of discharging relative to valve opening was recorded experimentally. It is found that the most intense signal is achieved when the time delay is about 460 μs. The dependence of the spectral intensity of CH on the ratio of methane was studied at total pressure fixed at 3 atm and discharge voltage fixed at -4 kV. A theoretical model was proposed, by which the calculation agrees well with experimental results. The stable discharging process and relatively strong charging intensity result in intense CH radical beam, with a pressure ratio of CH4 to helium about 1∶99. Under the above ratio, the emission spectra of the (0,0) band in the A2Δ-X2Π system was detected and analyzed, and the vibration and rotational temperatures were determined to be about 4575 K and 2455 K, respectively. The CH number was estimated to be about 1013～1014 per pulse in this experimental condition.