Power spectral study of the classical vibrational dynamics of RDX

Power spectra are employed in a qualitative study of the classical vibrational dynamics of the hexahydro-1,3,5-trinitro-1,3,5-triazine molecule (RDX). The aim is to determine whether the dynamics are predominantly chaotic or nonchaotic for energies corresponding to either the zero-point level or those accessible via gas-phase infrared multiphoton excitation. The results indicate the existence of robust, well defined bands in the spectra; each of the chemically distinct internal coordinates yields a power spectrum that can be readily distinguished from those corresponding to other coordinates. However, the extent of intra-mode coupling is apparently greater - even at the zero-point energy - than for other, smaller polyatomic molecules that have been studied recently using similar techniques. Probable explanations for this behavior are proposed and possible implications for the reactive dynamics of large polyatomics are discussed.