Pressure-dependent mobility of negative ions in mixtures of H2O with Ar

• Published in: Journal of physics. D, Applied physics Vol. 49; no. 15
• Main Authors: de Urquijo, J, Ruiz-Vargas, G
• Format: Journal Article
• Language: English
• Published: IOP Publishing 14.03.2016
• Subjects: ion mobility; ionisation of plasmas; low-field and Townsend discharges; negative ions of water; transport properties; water ion clusters
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/49/15/155202

The mobility of negative ions in H2O-Ar mixtures has been measured with a pulsed Townsend technique. It has been found that for a fixed value of the density-normalized electric field strength, E/N, the mobility of the H2O anions is strongly pressure dependent. We have also found that even for a single, total gas mixture pressure, even though at first sight the mobility of the anions seems to follow Blanc's relation closely, a closer view indicates that the mobilities tend to shift to higher values as the water vapour concentration decreases. In spite of the lack of mass spectrometry to assess the mass and abundance of the drifting anions under specific conditions of E/N, water vapour concentration and gas pressure, the present measurements are strongly indicative of a complex ion transport and ion-molecule reaction scheme of daughter H2O anions in the H2O-Ar mixture.