An ion-driven permeation method was used, in which the implantation of energetic ions was used instead of gaseous or electrochemical charging. It was found that the results could be described by:

D (m2/s) = 1.4 x 10-6 exp[-35.7(kJ/mol)/RT]

T.Tanabe, Y.Furuyama, N.Saitoh, S.Imoto: Transactions of the Japan Institute of Metals, 1987, 28[9], 706-14