Abstract
The time sweeps of images of optical breakdown plasma flashes under irradiation of aqueous solutions of Fe nanoparticles with Nd: YAG laser radiation (λ = 1,064 nm, τ = 10 ns, ν = 10 kHz, ε = 2 mJ) are studied. It is shown that the sizes of plasma flares, the plasma glow intensity, and the time to reach the maximum intensity are concentrated around certain values. So, for example, the values of 30 μm are most typical for the maximum size of flares. The maximum luminescence is usually reached in 3–4 ns. It is found that at initial stage of optical breakdown process the water-vapor boundary moves at typical speed of 11 km/s and have maximum and minimum values at 15 and 4 km/s respectively. It is assumed in this work that such a distribution may be associated with the initiation of breakdown on nanoparticles located in different places of the laser radiation waist.
Highlights
Nowadays, the process of optical breakdown is being intensively studied [1,2,3]
Practical application is mainly associated with the process of laser ablation of metal targets in liquids for the generation of nanoparticles, as well as the LIBS and NELIBS methods, based on the study of plasma spectra induced by laser radiation on the surface of samples or on nanoparticles [4, 5]
It follows from the figure that the lifetime of an optical breakdown plasma flash is 15 to 30 ns
Summary
Practical application is mainly associated with the process of laser ablation of metal targets in liquids for the generation of nanoparticles, as well as the LIBS and NELIBS methods, based on the study of plasma spectra induced by laser radiation on the surface of samples or on nanoparticles [4, 5]. Other distinctive features of optical breakdown in a liquid are the processes of formation of decay products of liquid molecules as a result of interaction with the breakdown plasma, intense generation of shock waves, the formation of cavitation bubbles, etc. One of the main directions in this area is the study of the process of optical breakdown of liquids at early stages, i.e. at the moment of the formation of the breakdown plasma and the formation of the cavitation area [11]. The practical application of these results is closely related to medicine and laser surgery as lasers with femto- and nanosecond pulse duration often used in these areas [12, 13]
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