Temperature and density controlled measurements of a non-universal Efimov state in \textsuperscript{39}K

We perform measurements of the absolute location of the Efimov ground state $a_{-}$ near a Feshbach resonance in $^{39}$K. The peak location is measured by loss spectroscopy in low density clouds for temperatures from 20-500nk. The effects of temperature saturation on the resonance peak location $a_-$ and width $\eta$ are characterized and demonstrate that the peak emerges more clearly at lower temperatures, consistent with finite temperature theory. This is in contrast to a recent similar study\footnotemark which showed the resonance to be shifted and surpressed at lower temperatures. Only at higher densities nearer to degeneracy do we observe the anamolous effects described by\footnotemark[\value{footnote}]. An accurate scattering length map derived from the precise measurement of the accompanying Feshbach resonance permits the determination of $a_{-}/r_{vdW}=14.19(16)$, significantly deviating from the value 9.73 predicted by van der Waals universality. We further characterize the effects of the trimer state for positive scattering lengths by measuring both the atom-dimer decay rate and the three-body recombination rate for free atoms. \footnotetext{Wacker \emph{et al.} PRA 98. 052706 (2018)}