Wavelength Modulation Spectroscopy
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Fig. 19 Variation of a intensity I , b the baseline given by 1 corresponding R 1f , c I //I 1 across
the wavelength scan of the HHL-521 QCL during outdoor measurements of CO on 22 July 2019
Fig. 20 Variation of a I , b 2 , c I //I 2 and 1 //I 2 across the wavelength scan of the HHL-521
QCL at various time instants
Fig. 21 Summary of results of using the IM-normalized 1f and 2f WMS technique to detect ambient.
a CO, CO 2 and b water vapour
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Fig. 19 Variation of a intensity I , b the baseline given by 1 corresponding R 1f , c I //I 1 across
the wavelength scan of the HHL-521 QCL during outdoor measurements of CO on 22 July 2019
Fig. 20 Variation of a I , b 2 , c I //I 2 and 1 //I 2 across the wavelength scan of the HHL-521
QCL at various time instants
Fig. 21 Summary of results of using the IM-normalized 1f and 2f WMS technique to detect ambient.
a CO, CO 2 and b water vapour