Influence of helium metastable states on the E-H mode transition in an inductively coupled plasma

A helium (He) inductively coupled plasma (ICP) source combined with two diode laser systems with the wavelengths of 396.5 nm (2(1)S-4(1)P) and 1082.9 nm (2(3)S-2(3)P) was configured to investigate the influence of He metastable states on the E-H mode transition. The population densities of 2(1)S and 2(3)S states were measured by laser absorption spectroscopy as the functions of RF power, He pressure, and the distance from RF antenna. Correlations between the E-H mode transition and the population density ratio of the 2(3)S metastable state to the 2(1)S metastable state as well as the line intensity ratio (LIR) of the 3(3)D-2(3)S transition to the 3(1)P-2(1)S transition were investigated. The E-H mode transition of He ICP was analyzed by the electron impact ionization rate and it was confirmed that the 2(3)S metastable state plays a key role in the E-H mode transition.

Automated summary

This study investigated the influence of He metastable states on the E-H mode transition using a helium inductively coupled plasma (ICP) source and two diode laser systems. The population densities of 2(1)S and 2(3)S states were measured, and correlations between the E-H mode transition and the population density ratio of the 2(3)S metastable state to the 2(1)S metastable state as well as the line intensity ratio (LIR) of specific transitions were examined.