Changes of the electron dynamics in hydrogen inductively coupled plasma *

Changes of the electron dynamics in hydrogen (H 2 ) radio-frequency (RF) inductively coupled plasmas are investigated using a hairpin probe and an intensified charged coupled device (ICCD). The electron density, plasma emission intensity, and input current (voltage) are measured during the E to H mode transitions at different pressures. It is found that the electron density, plasma emission intensity, and input current jump up discontinuously, and the input voltage jumps down at the E to H mode transition points. And the threshold power of the E to H mode transition decreases with the increase of the pressure. Moreover, space and phase resolved optical emission spectroscopic measurements reveal that, in the E mode, the RF dynamics is characterized by one dominant excitation per RF cycle, while in the H mode, there are two excitation maxima within one cycle