The experimental observations in this paper indicate that cis-CH3ONO becomes enriched in inert-gas matrices relative to gas-phase abundances. Not only is this enrichment observed in the matrix, but the degree of this enrichment was also demonstrated to vary as a function of matrix host identity (N2, Ar, and Xe) and-in the case of N2-also depends on deposition angle. These observations are in contradiction to the conventional matrix-isolation assumption that gas phase abundances are transferred to the matrix phase upon deposition. To investigate the underlying chemical physics behind our observations, we turn to the literature on surface-mediated processes. In this section, we discuss how the effects of surface morphology and energetic stabilization contribute to the observed change in conformer abundance.