Relaxation of the orientation of the potassium resonance levels due to collisions with rare-gas atoms

Measurements of the collisional relaxation of the potassium resonance levels are reported. Effects due to the presence of nuclear spin are allowed for in the case of ²P_1/2 and found to be negligible in the case of ²P_3/2. Reasonable overall agreement is found with calculated cross sections based on the Pascale and Vandeplanque potentials (1974). The natural lifetimes of the resonance levels are found to be tau (²P_1/2)=25.0+or-0.3 ns and tau (²P_3/2)=26.3+or-1.0 ns, and the sum of the resonance values is in good agreement with recent SCF calculations.