A determination of the stabilities of H+3(H2)n with n=1–9 from measurements of the gas-phase ion equilibria H+3(H2)n−1 +H2=H+3(H2)n

The equilibria of clustering reaction H+3(H2)n−1 +H2=H+3(H2)n were studied over the temperature range 330–25 K. The experiments were done with a pulsed electron–beam mass spectrometer. The ion source was thermostatted using a temperature-regulated cryocooler. The thermochemical stabilities of H+3(H2)n with n=1–9 were determined. The ions H+5, H+9, H+15, and H+19 are relatively more stable toward dissociation. The enthalpy changes for the clustering reaction yielding H+5 and H+7 were found to be in good agreement with the recent experimental study of Beuhler, Ehrenson, and Friedman, but in somewhat poor agreement with the earlier examination by Hiraoka and Kebarle.