Chemistry Reference
In-Depth Information
limits for the image of Figure 1. The regions of zero slope (crest and
troughs) in the image (detection system aligned to accept the specular re-
flection from a flat surface) were determined from the complimentary im-
age of the reflected incident pump laser beam footprint and timing from
the wave slope detector.
Peak #1
0.338 Pg/cm
2
Peak#2
0.322 Pg/cm
2
Trough #1
0.282 Pg/cm
2
Trough #2
0.218 Pg/cm
2
Fig. 1.
An intensity scaled SHG image of surfactant concentration on a 2.0 mm
wavelength standing circular capillary wave is shown above using a grey scale
with darker indicating a stronger signal. The equilibrium (no waves) surfactant
concentration was 0.288 Pg cm
-2
. The image was obtained with a single 3 nano-
second laser pulse and the imaging system was optically aligned to capture the
signal from the regions of zero slope (crests and troughs-the darker bands in the
image). The image is 80 by 80 pixels on edge (0.81 mm/pixel in the y axis and
0.22 mm/pixel in the x axis due to the 60 degree angle of incidence). Indicated on
the image are regions corresponding to peaks and troughs of the wave. For each of
these regions, concentrations of the insoluble hemicyanine monolayer are indi-
cated. These concentrations are obtained by averaging the individual pixel con-
centrations along the crest or trough for that particular extremum. The region indi-
cated as 'Peak #1,' is the tank centre.
All of the individual frames analysed in these experiment show trends in
surfactant concentration variation: an increase in surfactant concentration
at the crest of the wave and a decrease in surfactant concentration at the
