Observation of atomic-pair absorption with an incoherent source.
We report the observation of atomic-pair absorption in barium and in barium-thallium vapors using a white-light source. At atomic densities on the order of 10(17) atoms/cm(3) we measure absorptions of 2.9% cm(-1) for Ba-Ba and 2.3% cm(-1) for Ba-TI. In both cases, the absorption maxima occur at the predicted (R = infinity) wavelength and have a full width at half maximum of approximately 15 cm(-1).