Pulse-resolved and averaged dynamics of stimulated Raman scattering, plasma emission, and acoustic waves in water and ethanol-water solutions

Laser-induced breakdown (LIB) in liquids involves complex and dynamic processes. This study reports the first pulse-resolved measurements of backward or forward stimulated Raman scattering (BSRS/FSRS), captured synchronously with plasma emissions, and acoustic signals during LIB in water and ethanol-water (EtOH-water) mixtures, using 532 nm nanosecond pulses at 10 Hz. O–H SRS bands show pronounced shot-to-shot variability, revealing transient hydrogen-bond (HB) networks and supporting a continuum of HB configurations, whereas C–H bands, plasma, and acoustic signals remain comparatively stable. Increasing the EtOH concentration reduces the main O–H peak and enhances lower-wavenumber O–H features in the average BSRS spectra, indicating HB structural changes and a transition at 16% EtOH by volume. Plasma profiles vary with EtOH content and laser power, correlating plasma position with self-focusing distance and linking molecular structure to plasma behavior. Acoustic amplitudes decrease with increasing EtOH concentration, due to reduced density and cavitation effects, stabilizing after initial pulses. These findings demonstrate the value of pulse-resolved analysis in revealing dynamic processes masked in averaged data. This approach offers new insights into HB dynamics, plasma evolution, and acoustic responses under intense laser irradiation, with implications for spectroscopy, plasma physics, and fluid dynamics.