Trace Gas Detection from Plant Leaves, Flowers and Seeds Using Conventional and Photothermal Light Deflection Spectroscopy

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Photothermal deflection spectroscopy is a method used indirectly to measure optical absorption of a sample. Different techniques can be employed to measure the amount of deflection, hence evaluate optical absorption of sample. This work investigates an alternative method both in principle and technique to measure sample’s optical absorption. The new method employed for the first time, relies on the simple idea of light beam deflection from the medium under investigation as a result of change in the index of refraction in its vicinity. The amount of deviation executed by the deviated beam is estimated using new technique that is used for the first time in deflection spectroscopy. As the deviated beam is allowed to pass through a single slit, the value of beam deflection is estimated from the resulting diffraction pattern, i.e. indicating the value of changes taking place in the sample and or measure sample’s optical absorption. The new detection technique used in the estimation of probe beam deflection was also applied in photothermal spectroscopy. Results from both methods were compared and revealed the ease of use of the new method, in addition it cuts cost and experimental efforts although its sensitivity is less than the conventional photothermal method.