In 1996, Garetz et al. discovered that supersaturated aqueous solutions of small organic molecules such as urea and glycine, irradiated with intense near-infrared (NIR) nanosecond laser pulses, nucleated orders of magnitude faster than identical unirradiated solutions, and called this phenomenon nonphotochemical laser-induced nucleation (NPLIN) [1]. In 2010, Yuyama et al. discovered that thin films of supersaturated solutions of glycine in heavy water on a glass substrate, irradiated with a tightly-focused intense NIR continuous-wave (cw) laser beam, formed a new millimeter-sized liquid phase centered at the beam focus, with a much higher supersaturation than the surrounding solution. They called this new phase a “dense liquid droplet” (DLD) and attributed its formation to trapping of glycine clusters by optical gradient forces. In spite of its extremely high supersaturation, this phase did not spontaneously nucleate while the beam was focused at the solution-substrate interface, but immediately nucleated when the focus was moved to the solution/air interface [2]. In this talk, we report that the irradiation of a DLD of glycine and heavy water with a single, unfocused 0.4-GW/cm2 7-ns 1064-nm laser pulse results in the nucleation of glycine, while irradiation of the same 136%-supersaturated solution before formation of the DLD results in no nucleation. Additional features of the DLD will also be discussed. These findings have implications concerning the nature of the DLD.

Nonphotochemical laser-induced nucleation of a “dense liquid droplet” of aqueous glycine formed by optical gradient forces

2019 Spring National Meeting

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