  High intensity pulsed neutron scattering reveals a new set of magnetic
excitations in the pinwheel valence bond solid state of the distorted kagome
lattice antiferromagnet Rb$_2$Cu$_3$SnF$_{12}$. The polarization of the
dominant dispersive modes (2 meV $<\hbar\omega< $7 meV) is determined and found
consistent with a dimer series expansion with strong Dzyaloshinskii-Moriya
interactions ($D/J=0.18$). A weakly dispersive mode near 5 meV and shifted
"ghosts" of the main modes are attributed to the enlarged unit cell below a
$T=215$ K structural transition. Continuum scattering between 8 meV and 10 meV
might be interpreted as a remnant of the kagome spinon continuum [T.-H. Han et
al., Nature 492, 406 (2012)]
