The mobility of mass-identified protons in helium gas

The mobility of protons in helium gas has been measured by the 'four-gauze' electrical shutter method. Extrapolation of low field measurements to zero field gave the value of the mobility, corrected to 273 K, as 31.8+or-0.3 cm 2 V -1 s -1 . The gas temperature was 300 K. The H + ions were identified with a quadrupole mass spectrometry during mobility measurements. The helium gas pressure in the mobility tube was in the range 1.96-3.54 torr, and the hydrogen gas concentration was about 0.01%. H + ions were produced from the gas mixture by dc glow discharge. The measurement results compared with the value calculated from Langevin's polarization limiting theory showed a deviation of 7%, whereas the figure obtained from Dickinson's quantum mechanical calculations gave a deviation of 4%.