Low temperature phase transition in n-pentane C-60 clathrate: a Raman scattering study

We present results on Raman scattering from a C-60.n-pentane (C-60.(n-C5H12 )(0.88)(C7H8)(0.05)) clathrate crystal in the range 20-300 K. The Raman int ensity, in particular of the H-g modes, increases several times with loweri ng 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 orientatio nal phase transition in C-60.n-pentane similar to that observed for solid C -60. (C) 2000 Published by Elsevier Science B.V.