  Electron-photon temporal correlations in electron energy loss (EELS) and
cathodoluminescence (CL) spectroscopies have recently been used to measure the
relative quantum efficiency of materials. This combined spectroscopy, named
Cathodoluminescence excitation spectroscopy (CLE), allows the identification of
excitation and decay channels which are hidden in average measurements. Here,
we demonstrate that CLE can also be used to measure excitation's decay time. In
addition, the decay time as a function of the excitation energy is accessed, as
the energy for each electron-photon pair is probed. We used two well-known
insulating materials to characterize this technique, nanodiamonds with
\textit{NV$^0$} defect emission and h-BN with a \textit{4.1 eV} defect
emission. Both also exhibit marked transition radiations, whose extremely short
decay times can be used to characterize the instrumental response function. It
is found to be typically 2 ns, in agreement with the expected limit of the EELS
detector temporal resolution. The measured lifetimes of \textit{NV$^0$} centers
in diamond nanoparticles (20 to 40 ns) and \textit{4.1 eV} defect in h-BN
flakes ($<$ 2 ns) matches those reported for those materials previously.

Materials Science