Estimating the effective pressure from nanosecond laser-induced breakdown in water

Nanosecond laser-induced breakdown (LIB) in liquids (e.g., water) can produce dynamic high pressure and high temperature. However, since high pressure needs to negate the effect of high temperature to some degree, it is only partially effective. As a result, it is difficult to directly measure the effective pressure due to the transient and complex LIB process. Here, we presented a simple method based on Raman spectroscopy to indirectly determine the effective pressure caused by LIB in liquid pure H2O and low concentration H2O-H2O2 mixtures. By comparing the Raman shifts of the ice-VII mode for pure H2O and H2O H2O2 mixtures under laser pumping and static high pressure, the LIB effective pressure can be first estimated. The empirical equation was then derived base on the correlation of the LIB effective pressure to ice-VII-point stimulated Raman scattering thresholds for pure and mixture water solutions, which can be used to estimate the LIB effective pressures for other different mixture water solutions with the uncertainty of 0.14-0.25 Gpa. Hopefully, our study here would advance the measurements of effective pressure in the LIB process. (C) 2021 Optical Society of America

Automated summary

This study indirectly determined the effective pressure caused by LIB in liquid pure H2O and low concentration H2O-H2O2 mixtures using Raman spectroscopy, and derived an empirical equation to estimate the LIB effective pressures for other different mixture water solutions. The method provides a way to advance the measurements of effective pressure in the LIB process.