Low temperature phase transition in n-pentane C60 clathrate: a Raman scattering study

We present results on Raman scattering from a C60.n-pentane (C60.(n-C5H12)0.88(C7H8)0.05) clathrate crystal in the range 20–300 K. The Raman intensity, in particular of the Hg modes, increases several times with lowering temperature below 160–200 K accompanied by significant reduction of the linewidths. The onset of this peculiar temperature behavior correlates with the reported phase transition in n-pentane clathrate. We argue that these findings give a Raman scattering signature for a low-temperature orientational phase transition in C60.n-pentane similar to that observed for solid C60.