COLLISIONAL DEACTIVATION OF K IN THE HIGH-LYING S-2 AND D-2 STATES BYHE, NE, AND AR

By measuring time-resolved fluorescence signals, we have obtained radi ative lifetimes and total cross sections for collisional deactivation by He, Ne, and Ar of K n S-2 and (n-2)D-2 states (n=7-11). The radiati ve lifetimes obtained agree with those previously reported. The cross sections, in the range of 15-180 Angstrom(2), generally increase with increasing the principal quantum number. Their magnitudes for the n S- 2 and (n-2)D-2 states are similar. The results are closely related to the geometric size of the excited K states, and weakly dependent on th eir orbital angular momentum. Our case differs from the K-H-2, collis ion, in which the electron harpoon mechanism should be involved. Our c ase also differs from the collision of Na with rare gas; the latter e asily induces l-mixing (l greater than or equal to 2) of the same n. W e have also found that the relative efficiency for He and Ar is differ ent in quenching of the low-lying and the high-lying K states. When n is small, the total cross section of deactivation by He collision is l arger than that by Ar collision, but is reversed for the high-lying st ates. Detailed discussion on these phenomena is presented. (C) 1996 Am erican Institute of Physics.