Time-resolved optical probing of the non-equilibrium supercritical state in molecular media under ns laser-plasma impact

E Mareev and N Minaev and E Epifanov and I Tsymbalov and A Sviridov and V Gordienko, OPTICS EXPRESS, 29, 33592-33601 (2021).

DOI: 10.1364/OE.441690

We proposed a complex method based on a combination of shadow photography and time-resolved Raman spectroscopy to observe the non- stationary laser-induced supercritical state in molecular media. Shadow photography is applied for retrieving pressure values, while Raman spectroscopy with molecular dynamics for temperature estimation. Time resolution of 0.25 ns is achieved by varying the delay between the pump (creating an extreme energy delivery) and the probe laser pulses by the self-made digital delay electronic circuit . The proposed method was employed in liquid carbon dioxide and water. Under nanosecond laser pulse impact, the estimated temperatures and pressures (similar to 700 K and similar to 0.5 GPa) achieved in media are higher than the critical parameters of the samples. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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