Electrical Discharge Channel in Sodium Vapor Initiated by Resonant Laser Light

A z-discharge channel in sodium vapor was initiated by a laser beam, which was tuned to the sodium D resonance line (λ=589 nm). Applying a voltage sufficiently lower than the self-breakdown voltage, the discharge of ∼40 cm in length was initiated by laser radiation of modest power density. Streak-camera photographs showed that the laser-initiated discharge channel was produced just along the laser beam path. It was confirmed that the resonant laser light was very effective for the channel initiation.