Measurement of collision broadening of the calcium resonance line by low resolution spectroscopy

The Lorentzian half-widths of the Ca λ4227 Å (4s²¹S₀?4s4p¹P₁) line in the impact regime have been measured by low resolution spectroscopy. They were determined from measurements of the total absorption of both a white source and an emission line of the same transition. The absorption cells contained calcium at about 410°C with a perturbing gas of argon at pressures of up to about 50 cm of Hg. Corrections were applied to account for the width of the emission line and the non-transparency of the absorption cells. High resolution measurements of absorption profiles from a grating spectrometer are also described and the results of both methods are compared.