Measurement of the cross sections for collisional broadening of the intercombination transitions in calcium and strontium.

We employ an alternative technique for determining the Lorentzian linewidth based upon the simultaneous measurement of the vapor transmission and group-velocity delay outside the Doppler core of an optically dense transition. We apply this technique to measure the cross sections for broadening of the intercombination lines of calcium, 4s 'S0~4s4p Pi, and strontium, Ss 'S0~5s5p Pi, by collisions with argon, neon and the ground-state neutral vapor. We compare our measured results with calculated values as well as previously determined values by other workers.