Vapor pressure and thermodynamics of Bk-249 metal

The vapor pressure of ²⁴⁹Bk metal has been measured over the range 1100-1500 K, using combined target and mass spectrometric Knudsen effusion techniques. Vapor pressure data are combined with an appropriate estimate for the solid heat capacity and the estimated crystal entropy S°₂₉₈, to produce enthalpy, entropy, and free energy functions from 298 to 2000 K. The vapor pressures are described by the equations: Log₁₀ P(atm) = -(15 718 ±253)/T+578±0.21 [solid, 1107-1319 K], Log₁₀ P(atm) = -(14 902 ±244)/T+5.14±0.17 [liquid, 1345-1528 K] from which we calculate Δ H°₂₉₈ (2nd law) = 73 960±1150 cal/mol [solid], Δ H°₂₉₈ (2nd law) = 73 980±1120 cal/mol [liquid], and Δ H°₂₉₈ (3rd law) = 74 220±180 cal/mol [solid and liquid].