Diffuse Reflectance Spectroscopy
Diffuse reflectance spectroscopy (DRS) is a valuable
tool to measure the absorption spectrum of material adsorbed on
opaque solid samples. By comparing with results obtained for similar
materials in solution, one can answer questions such as "How
does a support material influence the photochemical behavior of
an adsorbed substrate?" or "How do the dynamics of charge
separation differ in a heterogeneous medium?"
At the NDRL, UV/visible and Fourier transform infrared spectrophotometers
are equipped with DRS attachments. In addition, we have a transient
absorption spectroscopy facility. A 532 nm laser pulse (10 mJ, pulse
width 6 ns) from a Quanta Ray DCR-1 Nd:YAG laser system is used
for excitation while the white light from a 1000 W Xenon lamp serves
as a probe. The diffusely reflected monitoring light from the sample
is collected and focused onto a monochromator which is fitted to
a photomultiplier tube. The transient signal is then digitized.
Using this setup we can obtain kinetic and mechanistic information
on photochemical transients generated on solid surfaces on the timescale
of 100 nanoseconds to 100 microseconds.