First laboratory detection of an absorption line of the first overtone electric quadrupolar band of N2by CRDS near 2.2 μm

Abstract

The extremely weak 2–0 O(14) electric quadrupole transition of N2has been detected by very high sensitivity Cavity Ring Down spectroscopy near 4518 cm−1. It is the first N2absorption line in the first overtone band reported so far from laboratory experiments. By combining a feedback narrowed Distributed Feedback laser diode with a passive cell tracking technique, a limit of detection of αmin ∼ 1.2 × 10−11 cm−1was achieved after one day of spectra averaging. The N22–0 O(14) line position and line intensity (about 1.5 × 10−30 cm/molecule) agree with calculated values provided in the HITRAN2012 database.