posted on 2021-12-27, 15:35authored bySergey I. Nikitenko, Tony Chave, Matthieu Virot, Rachel Pflieger
Splitting
of water molecules driven by ultrasound plays a central
role in sonochemistry. While studies of sonoluminescence revealed
the formation of a plasma inside the cavitation bubble, much less
is known about the contribution of plasma chemical processes to the
sonochemical mechanisms. Herein, we report for the first time sonochemical
processes in water saturated with pure CO. The presence of CO causes
a large increase in the H/D kinetic isotope effect (KIE) to αH = 14.6 ± 1.8 in a 10% H2O/D2O
mixture under 20 kHz ultrasound. The anomalous H/D KIE is attributed
to electron quantum tunneling in the plasma produced by cavitation.
In addition, CO2 formed simultaneously with hydrogen during
the sonochemical process is enriched with the 13C isotope,
which indicates a V–V pumping mechanism typical for non-equilibrium
plasma. Both observed KIEs unambiguously point to the contribution
of quantum effects in sonochemical mechanisms.