  In this article, we study the theoretical behaviour of all the possible
hyperfine transitions ($\pi$, $\sigma^+$ and $\sigma^-$) between the $5S$ and
$6P$ states of ${}^{87}\text{Rb}$ and ${}^{85}\text{Rb}$ atomic vapors under
the influence of an external magnetic field $B$. We show that, for specific
transitions, we obtain one or several $B$-values for which the transition
intensity is cancelled. The precision of these values is limited to the
uncertainty of the physical quantities that are involved in the problem, thus
measuring precisely the $B$-values for the cancellations could be a way to
determine these quantities more precisely. In the simplest cases involving
$2\times 2$ hamiltonians, we give eigenvectors, eigenvalues and analytical
formulas to determine the transition cancellation. By checking accuracy between
formulas and numerical simulations, we conclude that it is possible to use the
latter in order to determine all the cancellations even in the most complicated
cases.
