Damping of a monochromatic Langmuir wave of finite amplitude is studied numerically. Below a threshold initial amplitude A₀^* classic Landau damping occurs but close to but above A₀^*, the characteristic times t_min and amplitudes A_min at which the wave first ceases to damp scale with the difference $(A_0 - A_0^\star)$ as power laws, A_min is proportional to (A₀ - A₀^*)^beta and t_min is proportional to (A₀ - A₀^*)^-tau, where beta and tau are the critical exponents. Both direct examination of the electron phase space and the power-law indices show that, near the threshold A₀^*, trapping does not arrest damping at finite amplitudes A_min and times t_min. Instead, arrest of linear damping is found to be an effect due to organization of phase space into a positive slope for the average distribution function f_av around the resonant wave phase speed v_phi.

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