Hydrogen Lyman-alpha and Lyman-beta emissions from high-pressure microhollow cathode discharges in Ne-H₂mixtures

Abstract

We observed intense emission of the atomic hydrogen Lyman- (121.6 nm) and Lyman- (102.5 nm) lines from microhollow cathode discharges in high-pressure Ne (740 Torr) with a small admixture of H2 (up to 3 Torr). The atomic emission lines are spectrally clean with essentially no background of molecular emissions from the H2 Lyman and Werner bands. We attribute these atomic emissions to near-resonant energy transfer processes in the high-pressure discharge. In one case, near-resonant energy transfer between the Ne2* excimer and H2 leads to the formation of H(n = 2) atoms, a process similar to what was observed recently by Wieser et al (1998 J. Phys. B: At. Mol. Opt. Phys. 31 4589) in a high-pressure Ne/H2 mixture excited by energetic ion and electron impact. In the other case, near-resonant energy transfer between excited N* atoms (or vibrationally excited neon excimer molecules) and H2 leads to the formation of H(n = 3) atoms. The ratio of Lyman- to Lyman- emission intensity depends on the operating parameters of the discharge (gas pressure, gas mixture, discharge current) which supports the notion that different processes are involved in the formation of the H(n = 2) and H(n = 3) atoms, respectively.

Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

“…For the operating conditions described, Lyman-α flux was found to be greatest at a discharge current of 10 mA, which corresponds to an applied voltage of -1130 V. Though Lyman-α emission from MHCDs is known, it was important to assess generation and transmission through the LiF window for our particular device. Previous reports of these devices typically have them operating at pressures below 1 atm [20,24,25]. This demonstrates that Lyman-α can be successfully generated in the relatively high-pressure environment of our device and transmitted through the LiF window for photoionization use.…”

“…This specific class of plasma device, the micro-hollow cathode discharge (MHCD), is characterized by a small hollow in the cathode of the device in which Pendel electrons experience multiple collisions with the plasma gas [19]. For a neon:hydrogen admixture discharge gas, these interactions are known to produce neon excimers that through near-resonant energy transfer dissociate H 2 leading to Lyman-α (10.2 eV) photon emission [20]. The emission spectra from these devices are also known to be dependent upon the discharge gas composition, flow rates, and discharge current/voltage [18,21,22].…”

Electric and spectroscopic analysis of a pure nitrogen mono-filamentary dielectric barrier discharge (MF-DBD) at 760 Torr

“…Some of these applications concern photo-chemical treatment of water [Azrague K et al 2005, Gonzalez et al 2004, volatile organic compound (VOC) remediation [Biomorgi J et al 2005, Koutsospyros A et al 2004, biochemical decontamination and remediation of toxic gases [Herrman H W et al 1999], realisation of non-coherent vacuum ultraviolet (VUV: 100 nm < λ < 200 nm) or ultraviolet (UV: 200 nm < λ < 400 nm) sources [Kurunczi P et al 1999, Masoud N et al 2004, material deposition [Babayan S E et al 1998], H 2 generation for fuel cells and diesel reforming [Qiu H et al 2004, exhaust treatment [Dietz et al 2004] … As far as non-coherent radiation DBD sources are concerned, VUV sources are of topical interest for a variety of industrial purposes such as plasma processing [Kogelschatz U et al 1999], surface cleaning [Korfatis G et al 2002] and modification [Wagner H-E et al 2003, Borcia G et al 2003, sterilization, decontamination and medical care. Recently some emerging scientific investigations were performed in neon [Carman R J et al 2010].…”

Argon excimer emission from high-pressure microdischarges in metal capillaries

“…2 These two characteristics make microdischarges attractive as a source of excimer radiation which requires three-body collisions of excited atomic states. Indeed, excimer emission has been observed in microdischarges of Ne, 3 Ar and Xe, 4 ArF, 5 XeCl, 6 and XeI. 7 Limited enhancement in excimer intensity from single MHCDs has been achieved 4 by increasing gas pressure.…”