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Electron attachment rates αw, as a function of the pressure-reduced electric field E/P298 and mean electron energy <ε≳ have been measured for trace amounts (<10−3 Torr) each of c-C4F6 (perfluorocyclobutene), 2-C4F6 (perfluoro-2-butyne), 1,3-C4F6 (perfluoro-1,3-butadiene), c-C4F8 (perfluorocyclobutane), and 2-C4F8 (perfluoro-2-butene) in mixtures with N2 (pressures 500–2000 Torr) and Ar (pressures 500–1500 Torr) at T=298°K. The thermal attachment rates for these molecules were found to be 4.89×109, 1.77×109, 4.26×109, 4.05×108, and 1.56×109 sec−1 Torr−1, respectively. From the αw (<ε≳) data, the attachment cross sections σa(ε) as a function of electron energy ε have been determined using the swarm-unfolding technique and are reported. For all five perfluorocarbon molecules, σa(ε) are very large. They exhibit three distinct negative ion resonances with maxima at: ∼0.0, 0.19, and 0.80 eV for 2-C4F6; ∼0.0, 0.17, and 1.04 eV for 1,3-C4F6; ∼0.0, 0.22, and 0.48 eV for c-C4F8; and ∼0.0, 0.18, and 0.59 for 2-C4F8. For c-C4F6, only a shoulder with a possible maximum at ∼0.14 eV was observed, in addition to the maxima at ∼0.0 and 0.71 eV. Although the positions of the maxima in σa(ε) vary only slightly among these compounds, the magnitude of σa(ε) depends strongly on structure.

Articles you may be interested inCentroid molecular dynamics approach to the transport properties of liquid para-hydrogen over the wide temperature range Shunting arc plasma generation over a wide range of ambient pressure and ion extraction Rev. Sci. Instrum. 73, 860 (2002); 10.1063/1.1427667Reduced state relationship for limiting electrical conductances of aqueous ions over wide ranges of temperature and pressure System employing laser heating for the measurement of hightemperature properties of materials over a wide pressure range Rev. Sci. Instrum. 48, 632 (1977);We have investigated in drift tube mass spectrometers the identity and the transport properties of ions formed in CO, gas at pressures ranging from 10-4 to 762 torr. Under bombardment by low energy (20-100 eV) electrons in the ion source, the primary positive ion is predominantly coj, with traces of C+, 0+, and CO'. The predominant ion becomes oj at pressures above 100 J.L (0.1 torr), and clustering of CO, molecules to the 0; occurs even at pressures below I torr. Break-up of the clusters also occurs, the ion identity changing many times in the drift region. The zero-field reduced mobility of the oj ·(CO,). charge carrier is a function of pressure, and varies from (1.30±0.03) cm'/V·sec at 0.2 torr to (I.l8±0.03) cm 2 /V·sec at I torr. The sole negative ion produced directly by the electron bombardment is 0-, which clusters to form the stable ion CO). whose reduced mobility is (1.27±0.06) cm'/V·sec for EIN ~60 Td at all pressures below I torr. At much higher pressures and under somewhat different conditions (above 30 torr and using beta source ionization), ions in CO, are observed to form multiple clusters, the population distribution among the clusters being strongly dependent on gas temperature. The zero-field reduced mobility of the charge carrier is largely independent of the identity of the core ion, and varies with pressure from roughly 1.2 cm' IV·sec at 35 torr to about 1.0 cm'/V.sec at 762 torr. drift energy is small compared to the thermal energy, Ko is independent of E/N and has a magnitude called the zero-field mobility. Lasers typically operate at E/N well within this low-field region.

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