High-pressure Raman study on the guest vibration in the host cage of methane hydrate structure I

High-pressure Raman scattering measurements for the structure I of methane hydrate (MH) and methane deuterohydrate (MDH) have been performed at 296 K in order to observe the vibration of guest methane molecule in the host water cage. An analysis of the peak frequencies of the lattice vibrations of MH and MDH shows that the guest vibration in the large cage appears at ∼50 cm−1, being based on the clear distinction between the guest and host vibrations by deuteration of the host cage.