  The coherence characteristics of a tin-vacancy color center in diamond are
investigated through optical means including coherent population trapping
between the ground state orbital levels and linewidth broadening effects. Due
to the large spin-orbit splitting of the orbital ground states, thermalization
between the ground states occurs at rates that are impractical to measure
directly. Here, spectral information is transformed into its conjugate variable
time, providing picosecond resolution and revealing an orbital depolarization
timescale of ${\sim30{\rm~ps}}$. Consequences of the investigated dynamics are
then used to estimate spin dephasing times limited by thermal effects.
