OH can be generated by directly decomposing water using an
external energy source, such as an electromagnetic beam,
ultrasound and microwave [44]. When water is irradiated with
an electromagnetic beam (gamma rays), water molecules are
decomposed to OH, H+
, and aqueous electrons. Water molecules
can also be decomposed by a high-voltage discharge in water.
When high voltage pulses of approximately 10 kV, which has a fast
voltage rise time in nanoseconds, are added between two
electrodes installed with a narrow gap (a few centimeters)
between them, a flame is generated as water discharge is caused.
This generates localized high concentrations of OH. OH can also
be generated by ultrasound or microwaves [45]. When these
energy sources pass through water, localized pressure differences
with time generate microbubbles, which acquire vibration energy
and become unstable. These bubbles generate strong energy at
high temperatures and high pressures, and the water molecule is
broken down to OH and H+
.
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