Fig. 4 | Scientific Reports

Fig. 4

From: Mid-IR standoff measurement of ageing-related spectroscopic changes in bitumen in the 6 µm (1700 cm−1) region. Part 1: Measurement strategy and instrument design principles

Fig. 4

Tuning ranges for the three lasers chosen to span the carbonyl region, overlaid onto spectra for water vapour (6%vol) and ammonia (900 ppm) for a pathlength difference of 2.2 cm. The thermal and current tuning ranges show the full range of wavelengths accessible to each laser, and range corresponding to rapid injection current modulation, respectively. Y-axis absorbance figures translate directly into uncertainty in the measurement of asphalt.

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