Control and in-situ Diagnostics of N2 Vibrational Excitation with Hybrid AC-RF Plasma and Ferroelectric Electrode

Hybrid AC-RF discharges are a promising route for plasma-assisted ammonia synthesis, yet how hybrid waveforms redistribute energy into N2 vibrational modes and reshape discharge morphology remains poorly quantified. Here we study a hybrid AC-RF N2 ferroelectric barrier discharge driven by a 20 kHz AC voltage, with a sub-breakdown 13.56 MHz RF waveform applied between AC bursts and diagnose the plasma using synchronous ICCD imaging and time-resolved hybrid fs/ps N2 vibrational CARS over 13-40 torr. The ICCD images show that the hybrid AC-RF waveform broadens the discharge and distributes emission over a larger volume compared with AC-only operation, whereas RF alone remains strictly sub-breakdown with no visible emission. The N2 vibrational CARS spectra show that, over 13-40 torr, hybrid AC-RF plasmas populate vibrational levels up to v = 2 and yield N2 vibrational temperatures that are systematically higher than in the corresponding AC-only discharges, with the hybrid-induced enhancement in Tvib tending to increase with pressure and reaching up to ~1200 K at 40 torr. These results demonstrate that tailored AC-RF power coupling can efficiently channel energy into N2 vibrational modes, providing a tunable control on internal energy distributions for optimizing plasma-assisted ammonia synthesis and related electrified chemical processes.