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

 



Schematic of a single beam instrument....



Schematic of a double beam instrument.....


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

3 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

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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