Pressure shift and broadening of the 254-nm intercombination line of mercury by N₂

We have used laser absorption spectroscopy to study the collisional broadening and shift of the 254-nm 6¹S₀→6³P₁ intercombination line of Hg in the presence of N₂ for pressures below 400 Torr. This study comprises the first measurements of the proportionality constants for pressure broadening and shift of Hg due to N₂ in this pressure range, and the first high-precision measurements of these pressure effects on Hg for any foreign gas. We obtain -2.54(2)MHz/Torr for the shift and 9.01(4) MHz/Torr for the broadening (full width at half maximum) at 21°C (95% confidence interval). These results are important for ongoing experiments using optical pumping of mercury in tests of fundamental symmetries, as well as for characterization of interatomic forces and tests of the theory of collisional line broadening.