  Estimations of evaporation field values in atom probe tomography (APT)
literature are sparse despite their importance in the reconstruction and data
analysis process. This work describes a straightforward method for estimating
the zero-barrier evaporation field ($F_E$) that uses the measured voltage vs.
laser pulse energy for a constant evaporation rate. This estimate depends on
the sample radius of curvature and its specific heat ($C_p$). If a similar
measurement is made of the measured voltage vs. base temperature for a fixed
evaporation rate, direct extraction of the material's $C_p$ can be made,
leaving only the sample radius of curvature as an input parameter. The method
is applied to extract $F_E$ from a previously published voltage vs. laser pulse
energy dataset for CdTe ($18.07 \pm 0.87~\mathrm{V~nm^{-1}}$); furthermore,
using the published voltage vs. base-temperature sweep of CdTe permits
extraction of a specific heat ($11.27 \pm 2.54~\mathrm{J~K^{-1}mol^{-1}}$ at
$23.1~\mathrm{K}$) in good agreement with the literature
($11.14~\mathrm{J~K^{-1}mol^{-1}}$ at $22.17~\mathrm{K}$). The method is then
applied to the previously uncharacterized material
tris[2-phenylpyridinato-C2,N]iridium(III) ($\mathrm{Ir(ppy)_3}$), yielding $F_E
= 7.49 \pm 0.96~\mathrm{V~nm^{-1}}$ and $C_p = 173 \pm 27~\mathrm{J~K^{-1}
mol^{-1}}$; this $F_E$ is much lower than most materials characterized with APT
to date.
