Spectroscopic-network-assisted precision spectroscopy and its application to water
Roland Tóbiás, Tibor Furtenbacher, Irén Simkó, Attila G. Császár, Meissa L. Diouf, Frank M. J. Cozijn, J. Staa, E. J. Salumbides, W. Ubachs
Abstract
Abstract Frequency combs and cavity-enhanced optical techniques have revolutionized molecular spectroscopy: their combination allows recording saturated Doppler-free lines with ultrahigh precision. Network theory, based on the generalized Ritz principle, offers a powerful tool for the intelligent design and validation of such precision-spectroscopy experiments and the subsequent derivation of accurate energy differences. As a proof of concept, 156 carefully-selected near-infrared transitions are detected for H 2 16 O, a benchmark system of molecular spectroscopy, at kHz accuracy. These measurements, augmented with 28 extremely-accurate literature lines to ensure overall connectivity, allow the precise determination of the lowest ortho -H 2 16 O energy, now set at 23.794 361 22(25) cm −1 , and 160 energy levels with similarly high accuracy. Based on the limited number of observed transitions, 1219 calibration-quality lines are obtained in a wide wavenumber interval, which can be used to improve spectroscopic databases and applied to frequency metrology, astrophysics, atmospheric sensing, and combustion chemistry.