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Engineering

Nanosecond and Femtosecond Laser Photochemistry and Ablation Dynamics of Neat Liquid Benzenes

In this paper, femtosecond/nanosecond laser ablation mechanisms of organic liquids were discussed on the results of time-resolved molecular spectroscopy and macroscopic imaging techniques. We have succeeded in linking molecular-scopic mechanisms and macroscopic morphological changes. This figure shows a time-series of shadowgraphs of liquid toluene irradiated by a femtosecond laser pulse (300 fs, 248 nm, 90 mJ/cm2). A hemispherical black in each flame is a side view of liquid free surface. A white bar in the last flame represents 1 mm. In 10 ns after femtosecond laser pulse irradiation onto the liquid surface from the top, liquid surface starts swelling. Followingly, the formation and expansion of gas-like plume and a hemispherical shock wave were clearly observed until the microsecond time region. The initial expansion velocity of shock wave was estimated to be 3000 m/s or higher. In the sub-millisecond and millisecond time regions, droplet formation and liquid surface swaying were observed. By 100 ms, the liquid surface was restored to the original surface. In addition to this shadowgraphy, we have developed time-resolved surface scattering imaging with picosecond time-resolution and sub-micrometer spatial resolution.

*Reprinted with permission from The Journal of Physical Chemistry B, 106, 151-202, Copyright 2002, American Chemical Society.

 

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