Baseline correction method for second-harmonic detection with tunable diode lasers
✍ Scribed by H.Abbink Spaink; T.T. Lub; R.P. Otjes; H.C. Smit
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 761 KB
- Volume
- 183
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
To measure small absorbances in tunable diode laser infrared spectrometry, secondharmonic detection is often used. The spectrum obtained is the sum of the desired molecular line profile, a contribution of the laser emission profile and various types of noise. It is shown that the undesired contributions can be reduced significantly by subtracting a least-squares fitted low-degree polynomial from the spectrum, followed by applying a digital low-pass filter to the remainder. A theory is developed for estimating the systematic error introduced by this procedure. The method is applied in a calibration experiment for nitrogen dioxide in air at low part-per-billion by volume levels.