Collision-induced line-shape effects limiting the accuracy in Doppler-limited spectroscopy of H 2

Recent advances in theoretical calculations of ${\mathrm{H}}_{2}$ dissociation energies and ultra-accurate measurements of ${\mathrm{H}}_{2}$ transition frequencies give possibilities not only for testing QED and relativistic effects, but also for searching for physics beyond the standard model. In this paper we show that at the level of ${10}^{\ensuremath{-}4}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ the uncertainty of the Doppler-limited ${\mathrm{H}}_{2}$ line position determination is dominated by collisional line-shape effects. We question the paradigm that the unperturbed transition energy can be determined from linear extrapolation of the line shift to zero pressure.