Spectroscopic line parameters of water vapor for rotation-vibration transitions near7180 cm−1

Abstract

We present low uncertainty measurements of line parameters for 15 rotation-vibration transitions of water vapor in the wave number range of $7170.27--7183.02\text{ }{\text{cm}}^{\ensuremath{-}1}$. These experiments incorporated frequency-stabilized cavity ring-down spectroscopy and a primary standard humidity generator which produced a stable and accurately known amount of water vapor in a nitrogen carrier gas stream. Intensities and line shape factors were derived by fitting high-resolution spectra to spectral models that account for collisional narrowing and speed-dependent broadening and shifting effects. For most transitions reported here, we estimate the relative combined standard uncertainty of the line intensities to be $<0.4%$, of which approximately one half this value we ascribe to limited knowledge of the line shape. Our measured intensities and broadening parameters are compared to experimental and theoretical literature values. Agreement between our experimental intensity measurements and those derived by recent ab initio calculations of the dipole moment surface of water vapor is within 1.5%.