Atmos Gas Cells
The standard long pathlength gas cell range is now the new Atmos™ series of metal-bodied fixed-pathlength gas cells.
They have been optimised using the latest optical modelling tools to give maximum signal-to-noise.
Wide pathlength range (2.5 to 20m) and vacuum to 125 psi operation.
Up to 200 °C with heating jacket and Ni-coated aluminium body.
Gold mirrors (protected) and Viton or Kalrez 'O' ring seals.
CaF2 or ZnSe windows, purgeable transfer optics box and leverlock series baseplate mounting.
Optional features include: vacuum / gas inlet & outlet taps, pressure gauge, desiccant storage caps and purge bellows.
Model | A2.5 | A5 | A10 | A20 |
---|---|---|---|---|
Pathlength (m) | 2.5 | 5.0 | 10 | 20 |
Base pathlength (mm) | 104 | 139 | 250 | 455 |
Number of passes | 24 | 36 | 40 | 44 |
Volume (L) | 0.27 | 0.63 | 2.12 | 3.68 |
The Atmos™ range of cells are heatable to 200 °C with the addition of a heating jacket and temperature controller.
Why Atmos™?
- Optimized optical path for unmatched signal-to-noise
- Low cell volume for fast gas exchange
- Ni-coated Al cell bodies for improved thermal transfer from heating jackets. Also holds higher gas pressure than glass.
- Inert stainless-steel mirror substrates and avoidance of glues to prevent outgassing
- 125 psi (8.6 bar) maximum cell pressure
- Retrofittable heating jacket option for up to 200 °C
Which pathlength should I choose?
The absorbance of a gas depends on the distance travelled by the IR light beam through the gas sample. The relationship between absorbance, A, concentration, C, and pathlength, L, is given by Beer’s Law:
A = -log10 (I/I0) = a.C.L
Atmospheric concentrations of gases are usually expressed in C.L units of ppm.m – the number of molecules that would be encountered by the infrared beam across a 1.0 m path.
A gas at 0.1 ppm atmospheric concentration will absorb as much IR light over a pathlength of 100 m as would the same gas at 1 ppm over 10 meters or at 10 ppm over 1 meter.
Accordingly, the pathlength of cell should be chosen to give absorbance values within the spectrometer’s linear range for a given concentration. The following table may be taken as a guide:
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Gas name | formula | v (cm-1) | ppm.m | absorbance |
---|---|---|---|---|
Carbon dioxide | CO2 | 2360 | 100 | 0.4 |
Carbon monoxide | CO | 2170 | 100 | 0.04 |
Methane | CH4 | 3020 | 100 | 0.1 |
C2 to C6 n-alkanes | 2960 | 100 | 0.1 | |
Nitrogen dioxide | NO2 | 1630 | 100 | 0.15 |
Nitric oxide | NO | 1900 | 100 | 0.015 |
Sulfur dioxide | SO2 | 1370 | 100 | 0.09 |
Hydrogen sulfide | H2S | 1300 | 1000 | 0.002 |
Ammonia | NH3 | 960 | 100 | 0.12 |
Hydrogen chloride | HCl | 2940 | 100 | 0.04 |
Water | H2O | 1650 | 1000 | 0.2 |
Vinyl chloride | CH2CHCl | 950, 900 | 100 | 0.06 |
Acetaldehyde | CH3CHO | 2750 | 100 | 0.015 |
Benzene | C6H6 | 670 | 10 | 0.09 |
Toluene | C6H5CH3 | 730, 690 | 100 | 0.1 |
Methanol | CH3OH | 1040 | 100 | 0.1 |
Ethanol | CH3CH2OH | 1050 | 100 | 0.05 |
Carbonyl sulfide | COS | 2070 | 100 | 0.4 |
Nitrous oxide | N2O | 2235 | 100 | 0.15 |
Sulfur hexafluoride | SF6 | 950 | 10 | 0.4 |
Contact us
If you have any questions or require further information, please do not hesitate to email us at [email protected], call us on +44 (0)113 286 4536 or submit a contact form.