Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – II: Experimental verification

2016 ◽  
Vol 168 ◽  
pp. 245-256 ◽  
Author(s):  
Thomas Hausmaninger ◽  
Isak Silander ◽  
Weiguang Ma ◽  
Ove Axner
Keyword(s):  
Experimental Verification ◽  
Weak Absorption ◽  
Absorption Condition

scholarly journals Investigating the Relation between Absorption and Gas Concentration in Gas Detection Using a Diffuse Integrating Cavity

2018 ◽  
Vol 8 (9) ◽  
pp. 1630 ◽  
Author(s):  
Xue Zhou ◽  
Jia Yu ◽  
Lin Wang ◽  
Zhiguo Zhang
Keyword(s):  
Transition Point ◽  
Light Transmission ◽  
Tunable Diode Laser ◽  
Gas Cell ◽  
Weak Absorption ◽  
Gas Concentration ◽  
Non Linear ◽  
The Relationship ◽  
Absorption Condition ◽  
Oxygen Concentrations

The relationship between absorption and gas concentration was studied using a diffuse integrating cavity as a gas cell. The light transmission process in an arbitrary diffuse cavity was theoretically derived based on a beam reflection analysis. It was found that a weak absorption condition must be satisfied to ensure a linear relationship between absorbance and gas concentration. When the weak absorption condition is not satisfied, a non-linear relation will be observed. A 35 × 35 × 35 cm diffuse integrating cavity was used in the experiment. Different oxygen concentrations were measured by detecting the P9 absorption line at 763.8 nm, based on tunable diode laser absorption spectroscopy. The relationship between the absorption signals and oxygen concentration was linear at low oxygen concentrations and became non-linear when oxygen concentrations were higher than 21%. The absorbance value of this transition point was 0.17, which was considered as the weak absorption condition for this system. This work studied the theoretical reason for the non-linear phenomenon and provided an experimental method to determine the transition point when using a diffuse integrating cavity as a gas cell.

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