Drift Velocity of Ions in Oxygen, Nitrogen, and Carbon Monoxide

Varney, Robert N.

doi:10.1103/physrev.89.708

Cited by 125 publications

(29 citation statements)

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“…(20). Chapman assumed that the ion mobilities were the same under strong electric fields as they are in weak, fine weather, electric fields, whereas Varney's (1953) measurements of the velocities of positively charged nitrogen ions indicate that their mobilities under strong fields may be as little as one-third of the weak-field values. Further, in his calculations, Chapman used the applied electric field strengths directly and did not consider the enhanced field strengths that acted on the ions at the tips of his electrodes.…”

Section: An Examination Of the Point Discharge Processesmentioning

confidence: 99%

Lightning Rod Improvement Studies

Moore

Rison

Mathis

et al. 2000

Journal of Applied Meteorology

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Although lightning rods have long been used to limit damage from lightning, there are currently no American standards for the shape and form of these devices. Following tradition, however, sharp-tipped Franklin rods are widely installed despite evidence that, on occasion, lightning strikes objects in their vicinity. In recent tests of various tip configurations to determine which were preferentially struck by lightning, several hemispherically tipped, blunt rods were struck but none of the nearby, sharper rods were ''hit'' by lightning.Measurements of the currents from the tips of lightning rods exposed to strong electric fields under negatively charged cloud bases show that the emissions consist of periodic ion charge bursts that act to reduce the strength of the local fields. After a burst of charge, no further emissions occur until that charge has moved away from the tip. Laboratory measurements of the emissions from a wide range of electrodes exposed to strong, normalpolarity thunderstorm electric fields show that positive ions are formed and move more readily over sharp-tipped electrodes than over blunter ones. From these findings, it appears that the electric field rates of intensification over sharp rods must be much greater than those over similarly exposed blunt rods for the initiation of upwardgoing leaders.Calculations of the relative strengths of the electric fields above similarly exposed sharp and blunt rods show that although the fields, prior to any emissions, are much stronger at the tip of a sharp rod, they decrease more rapidly with distance. As a result, at a few centimeters above the tip of a 20-mm-diameter blunt rod, the strength of the field is greater than that over an otherwise similar, sharper rod at the same height. Since the field strength at the tip of a sharpened rod tends to be limited by the easy formation of ions in the surrounding air, the field strengths over blunt rods can be much stronger than those at distances greater than 1 cm over sharper ones.The results of this study suggest that moderately blunt metal rods (with tip height-to-tip radius of curvature ratios of about 680:1) are better lightning strike receptors than are sharper rods or very blunt ones.

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Section: An Examination Of the Point Discharge Processesmentioning

confidence: 99%

Lightning Rod Improvement Studies

Moore

Rison

Mathis

et al. 2000

Journal of Applied Meteorology

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“…The ions 0+, 0 2 + , 0 3 + , O", 0 2~, and possibly 0 3~ have been reported to exist, and most of their mobilities have been measured. [3][4][5][6][7] Once the mobility K of an ion is well established at room temperature as seems to be the case for 0 2 + in its parent gas, it is of great interest to measure K as a function of temperature. Obviously, such measurements in oxygen are not only of academic importance, since they can provide information of value to the study of the ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Ambipolar Diffusion in an Isothermal Oxygen Plasma at Elevated Temperatures

Mentzoni¹

1964

Phys. Rev.

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Electron removal in an afterglow discharge in oxygen was measured using microwave diagnostic techniques. For pressures below 1 mm Hg it was found that ambipolar diffusion was the principal loss process in the late afterglow which, by microwave radiation temperature measurements, was proven to be isothermal at the ambient gas temperature. A marked difference in the rate of diffusion for the low-and high-current discharge afterglow at room temperature was demonstrated with D a p values equal to 110±10 and 216±20 cm 2 sec -1 , respectively. The identity of the ions leading to the higher value is not well established since it is not clear how 0 + ions could be predominant in the high-current case. It is perhaps more probable that the ion C>3 + is responsible based on some reported mass spectrometric studies of the oxygen afterglow. The ions responsible for the lower D a p value, however, are most probably O2 4 " judging from previously published results. These ions display a strongly temperature-dependent diffusion rate in the range 300 to 900°K which on the mobility versus temperature plot resulted in a maximum of about 5.0 cm 2 sec -1 V -1 around 600°K after a steep climb from the value 2.8 cm 2 sec" 1 V" 1 at T=300°K; between 600 and 900°K the decline in mobility is only slight. This behavior is discussed in terms of ion-molecule force fields and charge transfer.

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“…The relative positions of processes [9] and [lo] in the sequence of ion/molecule reactions of allene are shown in Fig. 1.…”

Section: Kinetic Modelmentioning

confidence: 99%

“…Reaction [9] might be an isomerization process or a stabilization reaction giving unreactive C l o H l l + species toward allene molecule. The relative positions of processes [9] and [lo] in the sequence of ion/molecule reactions of allene are shown in Fig.…”

Section: Kinetic Modelmentioning

confidence: 99%