When hyperthermal beams of organic compounds strike a heated Re surface, their positive ions are scattered from that surface. Within the energy range studied (several eV), the efficiency of ion production is a function of incident kinetic energy (E-k) and surface temperature (T-s). This indicates that the ionization probability (I) correlates well with both E-k and 1/T-s. The conversion efficiency of translational to ionization energy in collisions of superthermal molecules with a surface was studied from the resulting ionization behavior. The gamma value, which is defined as a fraction of the kinetic energy used for ionization, is estimated from two unique E-k and T-s correlations. The gases used in this study were acetone, benzene, naphthalene, and alpha-pinene. The gamma value was molecule dependent. For example, at one extreme is the alpha-pinene molecule whose gamma value when derived from the I vs E-k relationship is 0.13 [the I(T-s) dependence gives gamma = 0.10 under the condition that E-k = 4.5 eV]. Thus the gamma values estimated from the two independent methods agree fairly well.