sample is not homogeneous and that the orange ink
comprises the top layer, followed by the blue ink layer and then the
polyethylene substrate. The
orange-to-blue phase difference is 5°
and the blue-to-polyethylene is 18°
which indicates an orange layer thickness of 0.8 mm and a blue layer
thickness of 2.9 mm
assuming that the thermal diffusivity is close to
10-3cm2/s for all layers and that the weaker absorption
strengths of the 1639 cm-1 and 1782 cm-1 bands do not
degrade the sharpness of boundary definition too much.
Figure 28. Amplitude
versus wavenumber and phase angle for a layered sample with two very thin (less
than approximately 5 mm)
ink layers.
The order of the layers is clearly defined from the data plotted in the
lower panel as orange ink/blue ink/polyethylene.
The phase scale zero is arbitrary.
