We are grateful to Dr Philip Camp for many useful discussions, and to an anonymous reviewer for pointing out a published correction to Eq. (5). We wish to acknowledge the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC) for supporting this work (EP/G067546/1), and to the Royal Society (London) for a research grant.

A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm(-2)) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm(-2)) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm(-2)). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

Results of experiments on laser-induced nucleation (LIN) in supersaturated (S = 1.20) aqueous ammonium chloride solutions are presented. Measurement of the particle-size distribution in unfiltered solutions near saturation (95%) indicates a population of nanometer-scale species with mean hydrodynamic diameter 750 nm, which is almost entirely removed by single-pass filtration through a poly(ether sulfone) membrane (0.2 m pores). Analysis of filter residues reveals iron and phosphate as major impurities in the solute. Experiments show that the number of nuclei induced by LIN can be reduced substantially by pre-processing (filtering or long-term exposure to laser pulses) and that this reduction can be reversed by intentional doping with iron-oxide (Fe 3 O 4) nanoparticles. The use of surfactant to assist dispersion of the nanoparticles was found to increase the number of laser-induced nuclei. We discuss the results with reference to mechanisms of nonphotochemical laser-induced nucleation (NPLIN).

Non-photochemical laser-induced nucleation (NPLIN) of glacial acetic acid (GAA) is demonstrated. The fraction of samples nucleated depends linearly on peak laser power density at low powers (<100 MW cm(-2)) with a threshold of (9.0 ± 4.2) MW cm(-2); at higher laser powers the fraction reaches a plateau of 0.75 ± 0.24 (2σ uncertainties). A simple model based on polarizability of pre-nucleating clusters gives a value of the solid-liquid interfacial tension γ(SL) = 15.5 mJ m(-2). It is hoped that the results will stimulate new developments in experimental and theoretical studies of cluster structure and nucleation in liquids.

We report the observation of non-photochemical laser-induced nucleation (NPLIN) of sodium chlorate from its melt using nanosecond pulses of light at 1064 nm. The fraction of samples that nucleate is shown to depend linearly on the peak power density of the laser pulses. Remarkably, we observe that most samples are nucleated by the laser back into the enantiomorph (dextrorotatory or levorotatory) of the solid prior to melting. We do not observe a significant dependence on polarization of the light, and we put forward symmetry arguments that rule out an optical Kerr effect mechanism. Our observations of retention of chirality can be explained by decomposition of small amounts of the sodium chlorate to form sodium chloride, which provide cavities for retention of clusters of sodium chlorate even 18 °C above the melting point. These clusters remain sub-critical on cooling, but can be activated by NPLIN via an isotropic polarizability mechanism. We have developed a heterogeneous model of NPLIN in cavities, which reproduces the experimental data using simple physical data available for sodium chlorate.