An atmospheric pressure plasma torch is generated with a hollowneedle-to-plate dielectric barrier discharge and the electron densities in the inside and at the surface of the plasma torch are measured by optical emission spectroscopy (OES). A plasma torch with lcm long is generated in atmospheric ambient when argon gas is introduced through the hollwneedle. The Stark broadenings of Hot and Ar I ( 696. 54 nm) lines, which are decomposed from the experimental profiles by using deconvolution method, are used to estimate the corresponding electron densities. The electron densities are 1.0 × 1015 cm-3 and 3.78 × 1015 cm-3 corresponding to the Stark broadening of Hα and Ar I (696.54 nm) lines,respectively. The electron density calculated from the Stark broadening of Hα is the same as that at the surface of the plasma because Hα line originates from the dissociation and the excitation of H2O at the plasma torch surface where argon can meet with atmosphere. While the electron density calculated from the Stark broadening of Ar I (696. 54 nm) line is the same as that in the insid of plasma.%利用空心针-板放电装置产生了大气压等离子体炬,采用光谱法测量了其内部及表面的电子密度.向空心针中通人氩气,在大气环境中产生了长度为1cm的等离子体炬.实验分别测量了Hα谱线和Ar Ⅰ(696.54 nm)谱线,通过反卷积方法分离出其相应的Stark展宽,并由此计算了电子密度.结果发现,采用Hα谱线和Ar Ⅰ(696.54 nm)谱线Stark展宽计算得到的等离子体的电子密度分别为1.0×1015 cm-3和3.78×1015 cm-3.考虑到Hα谱线源于等离子体炬表层与周围大气接触时产生的大气中水分子的离解激发,Hα线Stark展宽计算得到的电子密度应为等离子体表层处的电子密度,而根据Ar Ⅰ(696.54 nm)谱线的Stark展宽得到的电子密度是等离子体内部的电子密度.
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