Knowledge Bank

Near IR spectra of the $\nu 2$ and $\nu 4$ bands of solid $AsH3$ and $AsD3$ are reported for the temperature range $13\circ K$ $-77\circ K$. These spectra indicate that the arsine molecules are undergoing rotational diffusion in phase II (above $32\circ K$). The spectral densities have been Fourier transformed to yield the dipole autocorrelation functions. Corrections have been made for the phonon contributions to the autocorrelation functions. The phonon-corrected autocorrelation functions have been calculated from free-rotor memory functions. The significance of this calculation with respect to rotational diffusion in plastic crystals is discussed.