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We show that there are two reasons why the partial width for the transition$\Gamma_1(\Upsilon(3S)\rightarrow \gamma\chi_{b1}(1P))$ is suppressed. Firstly,the spin-averaged matrix element (m.e.) $\bar{I(3S|r|1P_J)}$ is small, beingequal to 0.023 GeV$^{-1}$ in our relativistic calculations. Secondly, thespin-orbit splittings produce relatively large contributions, giving$I(3S|r|1P_2)=0.066$ GeV$^{-1}$, while due to large cancellation the m.e.$I(3S|r|1P_1)=-0.020$ GeV$^{-1}$ is small and negative; at the same time themagnitude of $I(3S|r|1P_0)=-0.063$ GeV$^{-1}$ is relatively large. These m.e.give rise to the partial widths: $\Gamma_2(\Upsilon(3S)\rightarrow\gamma\chi_{b2}(1P))=212$ eV, $\Gamma_0(\Upsilon(3S)\rightarrow\gamma\chi_{b0}(1P))=54$ eV, which are in good agreement with the CLEO andBaBar data, and also to $\Gamma_1(\Upsilon(3S)\rightarrow\gamma\chi_{b1}(1P))=13$ eV, which satisfies the BaBar limit, $\Gamma_1(exp.) <22$ eV.

Dominant spin-orbit effects in radiative decays {$\Upsilon(3S\rightarrow \gamma\chi_{bJ}(1P))$}}