λ=− 1 N ⋅ dN dt MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiabeU7aSjabg2da9iabgkHiTmaalaaabaGaaGymaaqaaiaad6eaaaGaeyyXIC9aaSaaaeaacaqGKbGaamOtaaqaaiaabsgacaWG0baaaaaa@4087@
in which N is the number of nuclei of concern existing at time t
où N est le nombre de noyaux existant à l'instant t