Before revision:  One can clearly observe the mixing process and distinguish tracer particles from the heavy and light fluids . Results in this paper are helpful for understanding the mechanism of complex compressible flow with Rayleigh-Taylor instability and present references for related particle tracking experiments .
After revision:  One can clearly observe the mixing process and distinguish tracer particles from the heavy and light fluids are not synchronous and the mixing of a RTI system is heterogenous. The results are helpful for understanding the mechanism of complex compressible flow with Rayleigh-Taylor instability and present references for related particle tracking experiments .