A new mass spectrograph has been constructed entirely of glass except for the electrodes. Furthermore its design reduces thermal dissociation to a minimum. Using this apparatus the products of ionization in carbon dioxide have been studied. The primary ions are found to be C${\mathrm{O}}_2^{+}$, C${\mathrm{O}}^{+}$, ${\mathrm{O}}^{+}$ and ${\mathrm{C}}^{+}$ appearing at 14.4, 20.4, 19.6 and 28.3 volts respectively. There is also some ${\mathrm{O}}_2^{+}$ produced as a secondary product with an ionization potential of 20.0 volts. Except for C${\mathrm{O}}_2^{+}$ minimum values for all the ionization potentials can be calculated and are found to agree within the limits of error with the observed values.

• Received 20 June 1930

DOI:https://doi.org/10.1103/PhysRev.36.472