Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

Abstract

Due to elevated pressure, cold atmospheric pressure plasmas generate excimer species, which can emit highly energetic photons, thus transferring energy inside the discharge and to treated substrates. However, they are difficult to assess, as they are absorbed by air or window material. Here, we present a method to measure vacuum ultraviolet photons using a monochromator with an aerodynamic window. The emission spectra of a radiofrequency‐excited atmospheric plasma jet were analyzed for typical gas mixtures. The data indicate that helium excimers contribute notably to the excitation of molecular and atomic species. The emission intensities do not follow densities of ground‐state species, underlining the variety of excitation channels and the change of the electron energy distribution function under changing gas composition.

Recent Advances in Surface Activation of Polytetrafluoroethylene (PTFE) by Gaseous Plasma Treatments

“…The plasma used by authors represents a source of VUV radiation arising from both argon dimers and oxygen atoms. The VUV from Ar dimers causes significant bond scission as revealed recently by [ 18 ], so the somewhat increased wettability upon treatment with pure Ar plasma can be explained by this effect. The VUV radiation is suppressed significantly upon the addition of another gas (oxygen in the case of Carbone et al), so a decreased wettability develops in the case of the Ar/O 2 mixture.…”

“…The results provided by Ohkubo et al, therefore, indicate a complex relationship between wettability, oxygen concentration and adhesion. The large surface concentration of oxygen, as determined by XPS, may be explained by extensive VUV radiation arising from He dimers [ 18 ].…”

Investigation of Surface Modification of Polystyrene by a Direct and Remote Atmospheric-Pressure Plasma Jet Treatment

“…Any transition to the ground state occurs at much lower wavelengths (i.e., in VUV range) and could not be probed by our optical spectrometer. According to Golda et al, the major radiation in the VUV range of Ar plasma occurs from the Ar 2 * continuum [1]. The spectrum in Figure 2 also shows a rather intensive OH band with the bandhead at approximately 309 nm.…”

“…Atmospheric pressure plasmas are also characterized by large gradients in reactive particles' density. Apart from reactive plasma species, atmospheric-pressure plasmas may be rather intensive sources of ultraviolet (UV) and/or vacuum ultraviolet (VUV) radiation [1]. Gaseous plasma at atmospheric pressure can be sustained in the air or any other reactive gas, but the preferred configuration employs noble gases.…”

“…Recently, Golda et al measured the UV/VUV radiation arising from APPJ sustained in He and Ar [1]. The gas flow rates were just above 1 slm, and a small admixture of O 2 or N 2 was added.…”