In experiments, the molecule is frozen within an inert gas matrix, which typically weakens the bonds and causes a redshift in the corresponding vibrational frequencies. This effect is particularly significant for hydrogen-bonded O-H stretches. Previous studies of glycine, the simplest amino acid, have shown that different inert gas matrices can produce varying redshifts due to the varying coupling strength between the matrix gas and the amino acid. Specifically, it was found that the argon (Ar) matrix can cause a redshift of nearly 100 cm⁻¹ for the hydrogen bonded O-H stretch in the Type II glycine conformer. Given the stronger basicity of the secondary amine in proline compared to the primary amine in glycine, we may anticipate a similar, if not greater, redshift for proline. Therefore, if a low temperature gas phase spectrum of proline were to be obtained via advanced spectroscopic techniques like isotopomer-selective photofragmentation vibrational spectroscopy, we expect that the hydrogen-bonded O-H stretch frequency would be around 100 cm⁻¹ higher than the current matrix spectrum due to the absence of matrix effects. This would result in a clearer peak separation of the hydrogen bonded O-H stretch from the C-H stretch region.