Ultraviolet - Visible Spectroscopy

In Ultravoilet/Visible (UV-Vis) spectroscopy, electromagnetic radiation is emitted within the wavelength range of about 200 to 800 nm from the source. The source is often a Deuterium (or hydrogen) lamp, a tungsten filiment lamp, or a xenon arc lamp. The radiation from the source is then passed through a wavelength selector (either a difraction grating or filter) through which a narrow band of wavelengths can pass. The sample is dissolved in some solvent which is contained in a sample container made of plastic, glass, or quartz. The beam from the wavelength selector passes through the sample and is absorbed by the sample according to Beer's law. The light that makes it through the sample is passed into a photomultiplier tube where the light intensity is recorded. There are many variations on this basic instrument design, such as double beam models where the light from the source is split and one half passes through a reference cell.

For more information on UV-Vis spectroscopy, goto http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/UV-Vis/spectrum.htm

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Schematic of a single beam instrument....

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Schematic of a double beam instrument.....

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Schematic of our single beam diode array spectrometer

The following are the instrument specifications of our UV-Vis instruments (single beam):

Specifications	S-T Model 340	LKB NovaSpec	Ocean optics Chem2000
Source	Tungsten halogen lamp	Tungsten halogen lamp	Tungsten Halogen and RF deuterium source
Readout	3½ digits; 2 modes: 0 - 100%T 0-1.999 A	3 modes: -.30 - 0.999 A -.30 - 1.999 A 1.0 to 100% T	2 modes: -.30 - 1.999 A - 0 - 100% T
Monochromator	Diffraction Grating, f 7 Ebert	1200 lines/mm holographic diffraction grating	N/A
Wavelength Range	330 - 1000 nm (extendable to 195 nm)	325 - 900 nm	250 – 850nm
Wavelength Accuracy	within 2 nm over full range	± 2 nm
Wavelength Repeatability	within 0.5 nm	± 1 nm
Spectral Bandwidth	8.0 nm nominal	12 nm
Stray Radient Energy	less than 0.5%	1% at 340 nm	<0.01%@600nm
Detector	solid state silicon device	single solid state silicon photocell	Diode array detector
Sample Holder	13 by 100	24 and 12 mm test tubes, standard and tall 10 mm cuvettes	10mm cuvettes
Outputs	0 - 1.0 VDC linear in transmittance	--------

For spectral scanning in 360, we use a Varian Cary 100 or an OceanOptics Chem2000.

The Chem 2000 UV-VIS spectrometer is a PC plug-in, 2048- element linear diode-array fiber optic spectrometer. It has an optical range from 250 to 850 nm and is mounted on a durable, half-length, 1 MHz analog to digital (A/D) card. The digital card fits easily into a slot in a personal computer. A delicate optical fiber cable goes from the light source and sample cuvette to the A/D card. where = Sample signal, =Dark intensity and = reference intensity.

Block diagram and Specifications of  the Cary 100 Double Beam Instrument

Specifications of the Cary 100 double beam instrument....

Source  Visible Source UV	tungsten halogen deuterium arc
Monochromator	Czerny-Turner
Wavelength Range	190-900 nm
UV-Vis Resolution	< 0.20 nm
Wavelength Accuracy	± 0.2 nm
Detector	R928 PMT
Grating	30 ´ 35mm, 1200 lines/mm