We have observed anomalous transparency in bound-free transitions of Cl 2 in pure Cl 2 and in Cl 2 -He and Cl 2 -Ar mixtures. From the dependence of transmitted laser energy on pressure, we have estimated the following collision diameters for C1 2 -C1 2 , Cl 2 -Ar, and Cl 2 -He collisions, respectively: 4.9, 4.4, and 1.5 A.