P.N.B. Neves

Experimental measurement of the mobilities of atomic and dimer Ar, Kr, and Xe ions in their parent gases.

A new experimental technique for measuring the mobilities of positive ions in their parent gases is presented. The technique was applied to the rare gases, Ar, Kr, and Xe, and, for pressures typically below 10 Torr, two different types of positive ions were observed. The reduced mobilities of these ions in their parent gases were measured as a function of E/N, the ratio of the electric field strength to the gas number density, at a temperature of 300±1 K. The results were compared with others available in the literature and the two ions were identified as being the atomic and the dimer rare gas ions. The results are in good agreement with those from other authors. Space charge and impurities effects are discussed.

Experimental ion mobility measurements in Ar-C2H6 mixtures

In this paper we present the experimental results for the mobility of ions in argon-ethane gaseous mixtures (Ar-C2H6) for pressures ranging from 6 to 10 Torr and for reduced electric fields in the 10 Td to 25 Td range, at room temperature. For Ar concentrations below 80% two peaks were observed in the time of arrival spectra which were attributed to ion species with 3-carbons (C3H7+, C3H8+ and C3H9+) and with 4-carbons (which includes C4H7+, C4H9+, C4H10+ and C4H12+ ions). For Ar concentrations above 80% a third peak appears, which may belong to C5H11+. The time of arrival spectra for Ar concentrations of 80%, 85%, 90% and 95% are displayed in the present paper as well as the reduced mobilities determined from the peaks observed for a typical reduced electric field used in gaseous detectors (E/N = 15 Td).

Experimental measurement of the mobility of ions originated in ethane in their parent gas

A recent experimental technique was used for measuring the mobility of positive ions originated from ethane in their parent gas. In this particular experiment, measurements were made in pure ethane (C2H6) for pressures ranging from 6 to 10 Torr and for reduced electric fields varying from 6 to 42 Td. The time of arrival spectra revealed two peaks and their reduced mobilities were determined. Extrapolation to zero field led to the values of 1.58 cm2V−1s−1 and 1.47 cm2V−1s−1, which are likely to belong to a 3-carbon ions group which includes C3H5+, C3H7+, C3H8+ and C3H9+ and to a 4-carbon ions group which includes C4H9+ and C4H10+ ions. For typical reduced electric fields used in gaseous detectors (E/N > 15 Td), the mobilities were 15% smaller than the Langevin limit [1].

Experimental measurements of the mobility of methane ions in methane

A recently used experimental technique for measuring the mobility of positive ions in their parent gases is applied to methane (CH4 purity ≥99.995%), where ion reduced mobility values K0 are deduced from the analysis of measured time-of-arrival spectra of the ions produced by a GEM. For CH4 pressures in the range 3 to 10 Torr, two peaks could be observed when reduced applied fields E/N were varied from 10 to 60 Td, where E/N is the ratio of electric-field strength to gas-number density. The corresponding extrapolated zero-field mobility values in CH4 were found to be K0 = 2.58 cm2 V−1 s−1 and K0 = 2.42 cm2 V−1 s−1, belonging likely to CH5+ ions on the 1st peak and to C2H5+ and C3H7+ ions, with similar mobility values and falling both under the 2nd peak.

A new contribution to the experimental measurement of the N4+ ion mobility in N2 at 298K

We measured the reduced mobility of the nitrogen, N4+, ion in N2, under different pressures and reduced electric fields at 298 K using a new technique. Extrapolation to zero field yields a value of 2.37 cm2V−1s−1, which is in good agreement with other published data.

Experimental Ion Mobility measurements in Ne-CO

In this paper we present the experimental results for the mobility, K0, of ions in neon-carbon dioxide (Ne-CO2) and carbon dioxide-nitrogen (CO2-N2) gaseous mixtures for total pressures ranging from 8–12 Torr, reduced electric fields in the 10–25 Td range, at room temperature. Regarding the Ne-CO2 mixture only one peak was observed for CO2 concentrations above 25%, which has been identified as an ion originated in CO2, while below 25% of CO2 a second-small peak appears at the left side of the main peak, which has been attributed to impurities. The mobility values for the main peak range between 3.51 ± 0.05 and 1.07 ± 0.01 cm2V−1s−1 in the 10%-99% interval of CO2, and from 4.61 ± 0.19 to 3.00 ± 0.09 cm2V−1s−1 for the second peak observed (10%–25% of CO2). For the CO2-N2, the time-of-arrival spectra displayed only one peak for CO2 concentrations above 10%, which was attributed to ions originated in CO2, namely CO2+(CO2), with a second peak appearing for CO2 concentrations below 10%. This second peak, with higher mobility, was attributed to CO2+ ions. The mobility values of the main peak range between 2.11 ± 0.04 and 1.10 ± 0.03 cm2V−1s−1 in the 1%–99% interval of CO2, while the second peaks from 2.26 ± 0.02 and 1.95 ± 0.04 cm2V−1s−1 (1%–10% of CO2). The inverse of the mobility displays an aproximately linear dependence on the CO2 concentration in the mixture.

_2

In this paper we present the results of the ion mobility measurements made in gaseous mixtures of argon (Ar) and methane (CH4) for pressures ranging from 5 to 8 Torr and for low reduced electric fields (in the 17 Td to 43 Td range), at room temperature. The time of arrival spectra of the several mixture ratios studied revealed that the relative abundance of the ions formed depend on the mixture ratios. For CH4 concentrations in the 2.5–10% range three well defined peaks were observed which were attributed to single-carbon ions (CH5+), 2-carbon ions (C2H4+ and C2H5+), and 3-carbon ions (C3H4+, C3H5+, C3H6+ and C3H7+). The time of arrival spectra for CH4 concentrations of 2.5% (P-2.5), 5% (P-5), 10% (P-10) and the reduced mobilities of the ions obtained from the peaks observed are presented in this paper. The ion mobility study was performed for typical reduced electric fields used in gaseous detectors (E/N > 15 Td).

and CO

We measured the reduced mobilities of the atomic, Ne⁺, and dimer, Ne₂⁺, ions in Ne, under different pressures and reduced electric fields, at 300 K. Extrapolation to zero field yields values of 4.4 cm² V^-1 s^-1 for Ne⁺ and 6.2 cm² V^-1 s^-1 for Ne₂⁺, which are in relative good agreement with other published data. The Ne⁺ ions are converted to Ne₂⁺ by a three-body reaction with a rate constant that was also measured. Its average value for reduced electric fields in the 8 to 12 Td range was (5.6 ± 0.1) × 10^-32 cm⁶ s^-1 at 300 K, also agreeing with the results from other authors using other techniques.

_2

We measured the reduced mobilities (k₀ in cm²V^-1s^-1) of the ions that are formed in P-10 mixtures under different pressures and various reduced electric fields. Two types of ions were identified. We then used the extrapolated values of k₀ when E/N¿0 (2.41 and 2.76 cm²V^-1s^-1), the Langevin formula and the Blancs law, to calculate the masses of these ions. Calculations indicate that the two ions have masses of 41 a.u. and 25 a.u., respectively. We propose hypothesis to explain the nature and origin of those ions.

-N

We have measured experimentally the mobilities of Ar ions in Ar at different pressures (1, 1/2, 1/4, 1/8 and 1/16 atm) and for low reduced electric fields (E/N < 10 Td). The results are in good agreement with those available in the scientific literature and they indicate that Ar2 + is the dominant ion species. The variation of the mobility with the pressure reveals the presence of the Ar3 + ions. Space charge and impurity effects were accounted.