EN
All-experimental self-quenching cross-sections σ_ nf ^q are reported for K(nf) states (n=5, 6, 7, 8). The experiment was performed at varied temperatures of K vapour in a spectral cell. Time-resolved fluorescence was observed following pulsed step-wise excitation with dipole and quadrupole transitions K(4s) K(4p) K(nf). The values: σ _ 5f ^q=2.4±1.7, σ_ 6f ^q=4.5±1.4, σ_ 7f ^q=8.1±1.8, and σ_ 8f ^q=18.2±3.0 (in units of 10^ -13 cm^ -1 ) were obtained from Stern-Volmer-type plots.