Enhanced localization of tunneling of the NH3 umbrella mode in nano-cage fullerene
Résumé
The infrared bar-spectrum of a single ammonia molecule encapsulated in nano-cage C60 fullerene molecule is modeled using the site inclusion model successfully applied to analyze spectra of CO2 isotopologues isolated in rare gas matrix. Calculations show that NH3 can rotate freely on a sphere of radius 0.184 Å around the site center of the nano-cage and spin freely about its C3 symmetry axis. In the static field inside the cage degenerate ν3 and ν4 vibrational modes are blue shifted and split. When dynamic coupling with translational motion is considered, the spectral signature of the ν2 mode is modified with a higher hindering barrier (2451 cm−1), an effective reduced mass (6.569 g mol−1) and a longer tunneling time (55594 ps) for the fundamental level compared to gas-phase values (2047 cm−1), (2.563 g mol−1) and (20.85 ps). As a result this mode is red shifted. Moreover, simulation shows that the changes in the bar-spectrum of the latter mode can be used to probe the temperature of the surrounding media in which fullerene is observed.