Quantum-tunneling-enhanced charging of nanoparticles in plasmas

The role of quantum tunneling effect in the electron accretion current onto a negatively charged grain immersed in isotropic plasma is analyzed, within the quasiclassic approximation, for different plasma electron distribution functions, plasma parameters, and grain sizes. It is shown that this contribution can be small (negligible) for relatively large (micron-sized) dust grains in plasmas with electron temperatures of the order of a few electronvolts, but becomes important for nanosized dust grains (tens to hundreds of nanometers in diameter) in cold and ultracold plasmas (electron temperatures at approximately tens to hundreds of Kelvin), especially in plasmas with depleted high-energy "tails" in the electron energy distribution.