Spectroscopic characterization of rovibrational temperatures in atmospheric pressure He/CH{sub 4} plasmas
- Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)
Atmospheric pressure of helium (He) and methane (CH{sub 4}) mixture discharge characteristics are investigated using emission spectroscopic methods. Plasmas are produced in a radio frequency capacitively coupled device at atmospheric pressure in the ambient air. Without the CH{sub 4} gas introduced in the plasma, the emission spectrum exhibits typical helium discharge characteristics showing helium atomic lines with nitrogen molecular bands and oxygen atomic lines resulting from air impurities. Addition of a small amount (<1%) of CH{sub 4} to the supplied He results in the emission of CN (B{sup 2}{sigma}{sup +}-X{sup 2}{sigma}{sup +}: violet system) and CH (A{sup 2}{delta}-X{sup 2} product : 430 nm system) molecular bands. Analyzing the CN and CH diatomic molecular emission spectra, the vibrational temperature (T{sub vib}) and rotational temperature (T{sub rot}) are simultaneously obtained. As input power levels are raised from 20 W to 200 W, T{sub vib} and T{sub rot} are increased from 4230 K to 6310 K and from 340 K to 500 K, respectively. On the contrary, increasing the CH{sub 4} amount brings about the decrease of both temperatures because CH{sub 4} is harder to ionize than He. The emission intensities of CN and CH radicals, which are important in plasma processing, are also changed along with the temperature variation. From the results, the atmospheric pressure plasma shows strong nonequilibrium discharge properties, which may be effectively utilized for thermal damage free material treatments.
- OSTI ID:
- 21254566
- Journal Information:
- Physics of Plasmas, Vol. 15, Issue 10; Other Information: DOI: 10.1063/1.3002397; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temperature measurement of an atmospheric pressure arc discharge plasma jet using the diatomic CN (B {sup 2}{sigma}{sup +}-X {sup 2}{sigma}{sup +}, violet system) molecular spectra
Optical and electrical characterization of an atmospheric pressure microplasma jet for Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures