Download (4Mb) - Etheses - Saurashtra University

Chapter VI UV-Vis Spectroscopic….
Some double-beam instruments have two detectors (photodiodes), and the
sample and reference beam are measured at the same time. In other
instruments, the two beams pass through a beam chopper, which blocks one
beam at a time. The detector alternates between measuring the sample beam
and the reference beam. An ultraviolet-visible spectrum is essentially a plot of
light absorbance or transmittance versus wavelength in a range of ultraviolet or
visible regions. Such a spectrum can often be produced directly by a more
sophisticated spectrophotometer. The wavelengths of absorption peaks can be
correlated with the types of bonds in a given molecule and are valuable in
determining the functional groups within a molecule.
Many researchers are interested in optical characterization of single
crystal. Some of these crystals are transparent to UV-Vis radiation while others
are not. For transparent crystals that have a negligible reflectance and
absorption, measurement of the transmittance is necessary for complete
optical characterization.
In the present study, single crystalline as grown crystals were used for
UV-Vis study without cutting and polishing them. The samples were prepared
for UV-Vis study in a standard manner by exposing equal area of sample and
blocking the other portion. A photograph of typical set up of UV-Vis
spectrophotometer is shown in figure (6.7).
Figure :6.7 A photograph of typical set up of UV-Vis spectrophotometer.
238