Behavior of Tantalum near the Critical Point at Femtosecond Laser Heating

The dynamics of the change in the complex-reflection coefficient of tantalum under the action of femtosecond laser pulses of moderate intensity is studied by the method of spectral microinterferometry with picosecond resolution. The features of the behavior of the amplitude and phase of the diagnostic wave in the modes of spall and fragmentation ablation are studied. The threshold and characteristic time of the development of explosive boiling of a tantalum target are estimated based on the analysis of the picosecond expansion dynamics.