Multiple activation energies for conversion of He(2 3S) atoms to He2(a 3Σu+) molecules in ternary collisions

Spatially resolved spectra of excited particles in homogeneous dielectric barrier discharge in helium at atmospheric pressure

In this paper, the optical emission spectra of He (3s(3)S-->2p(3)P, 706.5 nm), OH (A(2)Sigma-->X(2)Pi, 0-0), N(2) (C(3)Pi(u)-->B(3)Pi(g), 0-0, 337.1 nm), and N(2)(+) (B(2)Sigma(u)(+)-->X(2)Sigma(g)(+), 0-0, 391.4 nm) emitted from plate-plate electrodes configuration homogeneous dielectric barrier discharge in helium are recorded at atmospheric pressure. The spatially resolved measurements are performed and the asymmetry discharge mode of homogeneous dielectric barrier discharge is observed with electrical and optical measurements when the micro-impurity (N(2), H(2)O) exists. The effects of applied voltage and driving frequency on the spatial distributions of the emission intensity of He (3s(3)S-->2p(3)P) are also investigated. It is found that the spatial distributions of the emission intensities of He (3s(3)S-->2p(3)P), OH (A(2)Sigma-->X(2)Pi, 0-0), N(2) (C(3)Pi(u)-->B(3)Pi(g), 0-0), and N(2)(+) (B(2)Sigma(u)(+)-->X(2)Sigma(g)(+), 0-0) exhibit two peaks at 1 and 6 mm from the upper electrode respectively in the 7 mm gas gap and the emission intensities at 1 and 6 mm are about two to three times higher than those at 3-4 mm; when micro-impurity (N(2), H(2)O) exists, the asymmetry discharge mode of homogeneous dielectric barrier discharge can be observed, the emission intensities at 6 mm are about 1.4 times higher than those at 1 mm. Also, the main involved physicochemical processes are discussed.