Excitation Transfer for K₂ in High-Lying States by N₂

A K-N2 mixture is irradiated in a glass fluorescence cell with pulses of 710 nm radiation from an OPO laser, populated K2 (1Λg) state by two-photon absorption. The cross section for 1Λg →3Λg transfer in K2 is determined using molecular fluorescence spectrometry. The cell temperature is kept constant at 553 K. The N2 pressure is varied between 40 Pa and 400 Pa. The effects of K2-K collisions could not be neglected. These effects are subtracted out by using the results of the pure K experiment. The cross sections are (3.8±1.5)×10-15 cm2 for K2 (1Λg)+N2 → K2 (3Λg)+N2 and (8.9± 3.5)×10-15cm2 for K2 (3Λg) collisions with N2.