Equilibrium vapor pressures of the hydrogen getters DPB and DPPE. [1,4-diphenyl butadiene (DPB); 1,6-diphenoxy-2,4-hexadiyne (DPPE)]

The equilibrium vapor pressure of two hydrogen getters 1,4-diphenyl butadiyne (DPB) and 1,6-diphenoxy-2, 4-hexadiyne (DPPE) have been determined in vacuum (approx. 10/sup -7/ Torr) in the temperature range 23 to 75/sup 0/C by the Knudsen effusion technique. Vapor pressure values for these two getters have not been previously reported in the literature. In this study we have measured the vapor pressures of the two getters and from these data calculated their heats of sublimation. The hydrogen getters DPB and DPPE exhibited vapor pressures in the ranges 6.6x10/sup -7/-6.0x10/sup -4/ for DPB and 3.5x10/sup -7/-8.4x10/sup -5/ for DPPE in the temperature range of 23 to 75/sup 0/C. The heats of sublimation determined were 114 kJ/mole (27.1 kcal/mole) and 51.9 kJ/mole (12.4 kcal/mole) for DPB and DPPE respectively. Additional work is needed at lower base pressures in the vacuum system to prevent hydrogen pick-up by the getters. In addition, mass-spectrometric measurements of DPPE species produced during effusion will be required to fully characterize this getter.