High pressure Raman spectroscopy of Linear carbon chain encapsulated in isolated multiwall carbon nanotube*

Elusive measurements of the Longitudinal optical (LO) phonon mode frequency of isolated Cn@MWCNT systems (linear carbon chains encapsulated by multi-wall carbon nanotubes) were studied under extreme high pressure via Resonance Raman spectroscopy. The pressure-dependent frequency softening with increasing pressure is discussed in terms of a simple force constant model in which the spring constants present a dependence with pressure. The model allowed us to easily obtain both the Young’s modulus and the Gruneisen parameter associated to such LO mode. In particular, the Gruneisen parameter was found to be much higher than that of Graphene and CNTs. Additionally, the LO phonon lifetime was found to be decrease with increasing stress.