Asymmetry of superradiance under delayed excitation

It is shown that the asymmetric nature of the radiation emitted by a self-terminating neon laser (λ = 614.3 nm) is a consequence of the propagation of ionizing potential gradient waves that ensure the traveling nature of the excitation of a gas. A solution of the Maxwell-Bloch equations yields formulas relating the delay between the appearance of superradiance pulses from the opposite ends of a source to the velocity of propagation of these waves. Estimates obtained of the velocity of propagation of ionizing potential gradient waves in neon are in agreement with the available experimental data.