Abstract
In this paper, we report a study on the nucleation behavior of potassium sulfate (K2SO4) from aqueous solutions under the influence of unfocused nanosecond laser pulses. The objective is to contribute to the general understanding of the Non-Photochemical Laser-Induced Nucleation (NPLIN) mechanism. First, the influence of several parameters such as supersaturation as well as laser parameters (pulse energy, number of pulses, and laser polarization) on induction time, probability of nucleation and mean number of crystals in comparison with spontaneous nucleation was investigated. Then, we examined the influence of gas composition (i.e., degassing and gas bubbling (CO2 and N2)) of the supersaturated solutions on the NPLIN kinetics, showing no correlation between gas content (or nature) on the crystallization behavior. Our study questions the role of impurities within the solution regarding the mechanism of laser-induced nucleation.
Highlights
Non-photochemical laser-induced nucleation (NPLIN) is a crystallization phenomenon discovered by Garetz et al in 1996 [1] while performing second harmonic generation experiments on supersaturated urea solutions
The first results and observations by Garetz et al were explained by means of the optical Kerr effect (OKE): because of their anisotropic polarizability, the solvated molecules interact with the electromagnetic field of the laser light, which results in an alignment of the dipoles
By using atomic force microscopy and scanning electron microscopy, we ensured that the structure of the glass was not damaged by irradiation: The surface aspect of the inner side of the vials was found to be similar before and after irradiation, and the formation of shattered glass particles was unlikely (Figures S1 and S2 and Table S1)
Summary
Non-photochemical laser-induced nucleation (NPLIN) is a crystallization phenomenon discovered by Garetz et al in 1996 [1] while performing second harmonic generation experiments on supersaturated urea solutions. The first results and observations by Garetz et al were explained by means of the optical Kerr effect (OKE): because of their anisotropic polarizability, the solvated molecules interact with the electromagnetic field of the laser light, which results in an alignment of the dipoles. The cooperativity of this event occurring in pre-nucleation clusters results in crystal nucleation
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