Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense   Rubidium and Cesium Vapor
  Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers are 290 MHz for Rb; 2500 MHz for Cs. 
C. J. Erickson, D. Levron, W. Happer, S. Kadlecek, B. Chann, L. W.   Anderson, T. G. Walker