Dynamics of particles near the surface of amedium under ultra-strong shocks

Through nonequilibrium molecular dynamics simulations,we provide an atomic-scale picture of the dynamics of particles near the surface of a medium under ultra-strong shocks.This shows that the measured surface velocity v_(f)under ultra-strong shocks is actually the velocity of the critical surface at which the incident probe light is reflected,and v_(f)has a single-peaked structure.The doubling rule commonly used in the case of relatively weak shocks to determine particle velocity behind the shock front is generally not valid under ultra-strong shocks.After a short period of acceleration,v_(f)exhibits a long slowly decaying tail,which is not sensitive to the atomic mass of the medium.A scaling law for v_(f)is also proposed,and this may be used to improve the measurement of particle velocity u in future experiments.