Hugoniot of C$_{60}$ fullerite: new results*

Recently, we have experimentally studied shock compressibility of C$_{60}$ fullerite and sound velocity in shock-compressed fullerite at the pressure range up to $\sim$50 GPa [1]. In this work we present the results of new shock experiments executed with C$_{60}$ fullerite in the same pressure range. On the base of new experimental results, we have made some correction of our concept [1] of the processes occurring in C$_{60}$ fullerite at shock compression. In particular, the anomalous behavior of the rear surface velocity profiles was detected at pressure $\sim $9 GPa [1]. Additional experiments have shown that this anomalous behavior was caused by jump of the sound velocity in C$_{60}$ because of formation of more hard carbon phase. We assume that it is a polymerized C$_{60}$ phase. In the pressure region 9-25 GPa, destruction of this phase and formation of a graphite-like carbon occurs. With further growth of shock pressure, phase transition of the graphite-like carbon to a diamond-like phase is observed with a transition onset pressure $\sim $25 GPa. If shock pressures higher than $\sim $33 GPa, Hugoniot of C$_{60}$ is determined by the thermodynamic properties of the diamond-like phase. [1] V.V. Milyavskiy, A.V. Utkin, E.B. Zaretsky, A.Z. Zhuk, V.V. Yakushev, V.E. Fortov. AIP CP 706 (2004) 667.