To investigate changes in the conformer abundance between gas phase and different lowtemperature matrices, dilute samples of CH3ONO in different bath gases were condensed onto a cold substrate at an angle of α = 20°, and conformer abundances in the matrix were measured using matrix-isolation spectroscopy (see Fig. ). Due to the inherent narrow line width of matrix-isolated vibrational transitions, the cis and trans conformer transitions of CH3ONO are distinguishable, regardless of the spectral region.