High accuracy line positions of the v(1) fundamental band of (N2O)-N-14-O-16

The v(1) fundamental band of N2O is examined by a novel spectrometer that relies on the frequency locking of an external-cavity quantum cascade laser around 7.8 gm to a near-infrared Tm:based frequency comb at 1.9 mu m. Due to the large tunability, nearly 70 lines in the 1240-1310 cm(-1) range of the v(1) band of N2O, from P(40) to R(31), are for the first time measured with an absolute frequency calibration and an uncertainty from 62 to 180 kHz, depending on the line. Accurate values of the spectroscopic constants of the upper state are derived from a fit of the line centers (rms approximate to 4.8 x 10(-6) cm(-1) or 144 kHz). The v(1) transitions presently measured in a Doppler regime validate high accuracy predictions based on sub-Doppler measurements of the v(3) and v(3)-v(1) transitions. (C) 2018 Elsevier Ltd. All rights reserved.