[Fine structure branching ratio for K-Ar optical collision].

An optically thin gaseous mixture of K and low-density Ar is excited by the fixed frequency line 514.5 nm of the argon ion laser. The excited KAr molecule is dissociated into the K 4P1/2 or K 4P3/2. The branching ratio is defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic K D1 and D2 lines. The branching is determined in the Ar density range between 2 and 8 x 10(17) cm-3. The ratio of the dissociation rates and the fine structure changing cross section are obtained.