Noble-gas-induced collisional broadening of the6P12−6P32transition of T1 measured by Raman echoes

We implement the Raman echo for the first time in collision studies to measure the noble-gas-induced broadening of the $6P_{\frac{1}{2}}-6\mathrm{}{P}_{\frac{3}{2}}$ transition of atomic thallium. Except in the case of He, the measured broadening cross sections He 59(2), Ne 67(2), Ar 124(4), Kr 167(5), and Xe 204(6) ${\mathrm{\AA }}^2$ ($T=840\mathrm{}$ K), agree with those calculated assuming a pure van der Waals collisional interaction. Our measurements, sensitive to collisionally induced changes in axial velocity of ≳ 300 cm/sec, reveal that collisional velocity changes of that magnitude are not important in T1-noble-gas collisions.