Water-vapor absorption database using dual comb spectroscopy from 300 to 1300 K part I: Pure H2O, 6600 to 7650 cm-1

We present broadband dual frequency comb laser measurements of pure H2O absorption (natural isotopic abundance of 99.7 % H216O) from 6600 to 7650 cm -1 (1307-1515 nm) with a spectral point spacing of 0.0068 cm -1. Twenty-nine absorption spectra were collected at temperatures between 300 and 1300 K (+/- 0.81 % average uncertainty) and pressures ranging from 0.5 to 16 Torr (+/- 0.27 %) with an average residual absorbance noise of 7.4E-4 across the spectrum for all measurements. We fit measurements using a quadratic speeddependent Voigt profile to determine 17,030 absorption parameters for 5986 transitions found in HITRAN2020. The measured parameters include line strength, line center, self -broadening, and self -shift, along with their power -law temperature -dependence exponents, and speed -dependent self -width parameters. A second version of the retrieved parameters with fits that do not include speed -dependence is also presented. We explore various trends to enable parameter extrapolation for weak transitions that were not covered in this work. We measured line parameters for an additional 614 features not presently catalogued in the HITRAN2020 database. In aggregate, these updates improved RMS absorbance error by a factor of 2.6 on average, and the remaining residual is predominantly spectral noise. This updated database improves high -temperature spectroscopic knowledge across the 6600-7650 cm -1 region of H2O absorption. An accompanying paper (Part II) describes similar measurements and a new database for air -broadened H2O absorption.