Experimental determination of 129 Xe-Cs/Rb spin-exchange efficiencies due to binary collisions and van der Waals molecules in 129 Xe-N2 mixtures

Abstract Determining whether Cs or Rb yields higher spin-exchange efficiency has long been a critical question in hyperpolarized 129 Xe field; however, experimental comparisons remain limited. We present the measurements of spin-exchange efficiency for 129 Xe -Cs/Rb in 129 Xe : N 2 = 1 : 50 mixtures. Under the low magnetic field and short lifetimes van der Waals molecular regime, we have determined spin-exchange efficiency between 129 Xe -Cs/Rb by measuring spin exchange rate coefficient k se of 129 Xe -Cs/Rb and spin relaxation rate Rsd of Cs/Rb induced by 129 Xe. At identical gas composition and pressure conditions, the spin exchange efficiency of Cs is approximately 1.2-1.5 times that of Rb. We have derived an expression to enable prediction of spin exchange efficiency between 129 Xe-Cs/Rb for an arbitrary 129 Xe-N 2 mixture.