with the prediction of D’Incao and Esry [@DIncao:2009]: $\beta^{\rm sh}_{2\to 3}\sim a_3^2/a_2$ and $\beta^{\rm sh}_{1\to 3}\sim a_1^2/a_2$.

![(Color online) The relaxation rate constant for the 12-dimer and atom 3 as a function of the magnetic field $B$. The squares are data points from Ref. [@Lompe:2010]. The curves are our results for the total rate $\beta_3$ (solid line), the partial rate into atom 1 and a 23-dimer $\beta^{\rm sh}_{3\to 1}$ (dashed line), and the rate into an atom and a deep dimer $\beta^{\rm deep}_3$ (dashed-dotted line). The light solid line gives the total rate $\beta_1$ for the parameters obtained in Ref. [@Lompe:2010] while the vertical line marks the boundary of the universal region. []{data-label="fig:beta3"}](beta3.pdf){width="15cm"}

Fig. \[fig:beta3\] shows our results and the recent measurement [@Lompe:2010] for $\beta_3$. Between $590$ G and $730$ G, the energy of the $12$-dimer is smaller than the energy of the $23$-dimer and the relaxation channel into $23$-dimers is open. After the $23$-dimer crosses the $12$-dimer at $730$ G this relaxation channel is closed and only relaxation into deep dimers is possible. As the crossing is approached, the rate vanishes as $\sqrt{a_3-a_1}$ in agreement with the analytical result from Sec. \[sec:relaxation\]. Between 832 and 834 G, $a_1$ is 