SiH_4激光等离子体内H谱线的线型研究

PROFILES OF H BALMER LINES EMITTING FROM A LASER-INDUCED SILANE PLASMA

本工作利用光学多道分析仪(OMA Ⅲ)测量了脉冲TEA CO_2激光诱发的SiH。等离子体内H Balmer系的H_α,H_σ和H_γ线的线型。结果表明,三条谱线的FWHM(半值全宽度)随跃迁上能级的主量子数的增加而增加,即△λ_(1/2)(H_α)<△λ_(1/2)(H_β)<△λ_(1/2)(H_γ)。通过对等离子体内各类加宽机制的讨论,得出等离子体内谱线的主要加宽机制为Stark加宽。由H_α线的实验线型与Stark加宽理论线型的拟合,得到等离子体的两个重要参量,平均电子密度N≈10^(17)cm^(-3),电子温度T≈40000K。由H_β线的时间分辨测量得到等离子体的电子密度随时间的演变曲线。

Profiles of Hα,Hβ and Hγ lines, cmited from a TEA CO2 laser induced silane plasma, are measured with an optical multichannel analizer (OMA Ⅲ) The experimental results show that FWHM (full width of half maximum) of the three lines increases with the main quantum number of the corresponding upper level of the transiti ons, i.e. △λ1/2(Hα) < △λ1/2(Hβ) < △λ1/2(Hγ), this suggests that the dominant broadening mechanism of the lines is Stark broadening. Fitting the measured Hα profile to theretical data of Stark broadening, two parameters of the plasma are obtained: average electron density N = 1017cm-3 and electron temperature T = 40 000 K. From time tesolved measurements of Hβ profile, a curve of electron density versus time is derived.