As reported in Sections 3.2-3.3, conformer abundances of CH3ONO deposited in Ar indicate an enhancement of cis that does not change with deposition angle. Quantum chemistry calculations do not indicate strong energetic preference for cis:Ar or trans:Ar. As a result from the calculations, surface morphological effects are likely to contribute to the enhancement of the cis conformer. However, because we see no changes in cis enhancement with deposition angle, we conclude that surface morphologies do not change substantially with deposition angle. Contrary to the results in N2, we see enhanced cis abundance even at perpendicular deposition angles. We thus conclude that CH3ONO, even at perpendicular deposition, has sufficient time to diffuse and desorb at all angles studied, enabling the enhancement of cis due to trapping in surface pockets. We propose that the smaller van der Waals radius of the cis conformer enables enhanced trapping over the larger trans conformer, resulting in increased cis abundance in the matrices. However, we acknowledge that we cannot explicitly rule out that this initial enhancement of cis-CH3ONO occurs during the gas-phase portion of the deposition process, since our effusive source is much further from the cold substrate (~8 cm) than previous studies (assumed to be on the millimeter to centimeter scale based on schematics), allowing for more collisions and/or other processes that could enhance the lowest energy conformer, 102-107 although we believe it unlikely given the high isomerization barrier of this system.