Chemistry Reference
In-Depth Information
measurement of Figure 3 was carried out using one 532 nm laser pulse of
slightly less than 3 nanoseconds in duration. The 60 degree angle of inci-
dence used for the pump laser beam led to an elliptical footprint that ac-
counts for the two spatial resolutions of 0.21 mm per pixel and 0.07 mm
per pixel in the measurement.
Fig. 3.
Absolute hemicyanine monolayer concentrations just downstream of a
Reynolds ridge in a laminar channel flow. The concentration gradient was deter-
mined using reflected SHG imaging
5 Conclusions
While past work established that SHG and SFG are important and viable
in
situ
probes capable of measuring surfactant concentration gradients on the
ocean surface, the spatial resolution was limited in these experiments. In
order to resolve concentration gradient features of 1 cm or less in extent,
an areal SHG measuring technique was developed using a CCD camera as
the detector. An image splitting optical separator is key to this measure-
ment technique allowing one to capture both the reflected SHG signal im-
age along with the image of the reflected pump beam which allows us to
correct for the intensity variations in the pump beam. The technique is ca-
pable of measuring surfactant concentrations with a spatial resolution of
less than 1 millimetre and a temporal resolution of less than 3 nano-
