Evidence for laser-induced homogeneous oriented ice nucleation revealed via pulsed x-ray diffraction

The induction of homogeneous and oriented ice nucleation has to date not been achieved.
Here, we report induced nucleation of ice from millimeter sized supercooled water drops
illuminated by ns-optical laser pulses well below the ionization threshold making use of
particular laser beam configurations and polarizations. Employing a 100 ps synchrotron
x-ray pulse 100 ns after each laser pulse, an unambiguous correlation was observed
between the directions and the symmetry of the laser fields and that of the H-bonding
arrays of the induced ice crystals. Moreover, an analysis of the x-ray diffraction data
indicates that, in the main, the induced nucleation of ice is homogeneous at temperatures
well above the observed and predicted values for supercooled water.