Sound waves propagating through a liquid at ultrasonic frequencies have wavelengths many times longer than the molecular dimensions or the bond length between atoms in the molecule. Therefore, the sound wave cannot directly affect the vibrational energy of the bond, and can therefore not directly increase the internal energy of a molecule. Instead, sonochemistry arises from acoustic cavitation : the formation, growth, and implosive collapse of bubbles in a liquid. The collapse of these bubbles is an almost adiabatic process, thereby resulting in the massive build-up of energy inside the bubble, resulting in extremely high temperatures and pressures in a microscopic region of the sonicated liquid. The high temperatures and pressures result in the chemical excitation of any matter within or very near the bubble as it rapidly implodes. A broad variety of outcomes can result from acoustic cavitation including sonoluminescence, increased chemical activity in the solution due to the formation of primary and secondary radical reactions, and increased chemical activity through the formation of new, relatively stable chemical species that can diffuse further into the solution to create chemical effects (for example, the formation of hydrogen peroxide from the combination of two hydroxyl radicals following the dissociation of water vapor within collapsing bubbles when water is exposed to ultrasound).