  In this article, we correlate the internal stress and the characteristics of
a vibrational mode in wet foam. Using microscope images, we estimate the
average size of the bubbles in wet foam, at specific time intervals, over a
duration of twenty four hours. Raman spectra are also recorded at the same time
intervals, over the same time frame. We show that the internal stress,
originated from the macroscopic structural change of foam with ageing, can be
related to the observed Raman shift of the low frequency methylene rocking mode
of the constituent surfactant molecules in foam. In this report we also show
the capability of the Raman spectroscopy to reveal the crystallinity in foamy
materials, when studied for a longer period of time.
