Sub-percent accuracy for the intensity of a near infrared water line at 10670 cm$^{-1}$: experiment and analysis

TL;DR

This paper reports highly precise experimental measurements of a near-infrared water absorption line at 10670 cm$^{-1}$, achieving sub-percent accuracy and comparing results with advanced theoretical predictions.

Contribution

It introduces a geometrically derived formula for optical path length and provides the most accurate experimental line intensity measurement to date, improving agreement with theoretical models.

Findings

Line intensity measured with less than 0.3% standard deviation.

Overall uncertainty of 0.7% in the line intensity.

Recent theoretical models show improved agreement with experimental data.

Abstract

Laser measurements of the intensity of (201) 3$_{22}$ -- (000) 2$_{21}$ near-infrared water absorption line at 10670.1 \cm\ are made using three different Herriott cells. These measurements determine the line intensity with an standard deviation below of 0.3~\% by consideration of the new geometrically derived formula for the opt ical path length without approximations. This determination together with the current accepted value leads to an overall uncertainty of 0.7~\% of the experimentally assessed line intensity which is compared with previous {\it ab initio} predictions. It is found that steady improvements in the both the dipole moment surface (DMS) and potential energy surface (PES) used in the theoretical studies leads to systematic better agreement with the observation, with the most recent prediction agreeing closely with the experiment.