Electron Mobilities in Liquid Argon

Abstract

0.88 0.65 85% -0 FIG. 2. Disintegration scheme of Os 186 .and the disintegration scheme are correct, the atomic mass difference between Os 185 and Re 185 may be estimated. This turns out to be about 1.0 Mev if the transition to the 0.88-Mev level is assumed to be first-forbidden, and slightly lower for an allowed transition.The fraction of the total K capture to the ground state has been reported 8 to be no greater than 0.10. The amount of L capture feeding the excited states could not be estimated at that time and hence was not considered. The presence of L capture changes this value to 0.20, but does not essentially alter the interpretation of this transition as first-forbidden, in agreement with the shell model. * This work was assisted by the joint program of the ONR and AEC.T HE internal conversion electron spectrum of Hg 199 ' 200 resulting from the orbital electron decay of Tl 199 -m has been studied with a small 180° shaped field spectrometer. The thallium isotopes were produced by alpha-particle bombardment of gold in the Indiana University cyclotron, and were separated from the target material by standard chemical procedure. Carrier-free sources were obtained by electrodeposition of the thallium from a solution containing no gold or mercury. With a plating current of 150 ma, the major part of the activity was deposited on the platinum electrode within one to two hours. The deposit was removed from the electrode with nitric acid and laid down by evaporation on a thin zapon film.A survey of the negatron spectrum showed the presence of twenty-five internal conversion lines, all of which decayed in intensity with either the 7-hour half-life of Tl 199 or the 27-hour half-life of Tl 200 . An analysis of the conversion lines of Tl 199 shows that they arise from nine gamma-rays of energies 49, 78, 103, 157, 206, 245, 332, 454, and 490 kev. For Tl 200 the observed conversion lines correspond to six gamma-rays of energies 365, 577, 622, 829, 1210, and 1360 kev. The figures quoted are accurate to within one percent.In the case of Tl 199 the results are in agreement with those of Hole, 1 who has found gamma-rays at 155 and 360 kev associated 1.360 fe-*^-1.212 0.365 0829 [ ' **'' • : i 0.577 0.622 ; FIG. 1. A possible disintegration scheme for Tl 200 . It is to be noted that the 1.212-Mev gamma-ray is not the cross-over for the cascade gammarays. The assignment of the 15-kev discrepancy as shown is arbitrary.with an isomeric 43-minute activity in Hg, which has been assigned 2 to Hg 199 . Scintillation spectrometer studies offer further evidence that these gamma-rays are coupled. It is found that the 157-and 332-kev gamma-rays are of about the same intensity and are probably in cascade. The 490-kev gamma-ray may be interpreted as the cross-over for these transitions. Similarly, the 245-and 206-kev gamma-rays are about equal in intensity and may be regarded as a cascade pair, with the 454-kev gamma-ray resulting from the alternative cross-over transition.The first five gamma-rays of Tl 199 listed above have essentia...

Ion mobility and liquid motion in liquefied argon

“…However, as has been shown (Kopylov 1964), liquid flow should tend to become independent of E d when Im is small, and since the characteristics of figure 9, which extend to low currents, are strikingly similar, it would appear that the variation of ci is probably due to the mobility p varying as Ed-112. Malkin and Schultz (1951) using a single 'a' pulse method also found that the mobility of a negative carrier in argon varied inversely as the square root of the field. At that time the carrier was considered to be a free electron, but the suggestion has since been made that it was more likely to be a negative impurity ion (Swan 1960).…”

“…There have been several reports of the mobility of positive and negative ions in liquefied argon, and in common with most dielectric liquids the values lie in the range 10-3-10-4 cm2 v-1 s-1. A second negative charge carrier has also been detected, which is probably a quasi-free electron with an apparent mobility which can exceed 102 cm2 v-1 s-1 (Davidson and Larsh 1948, 1950, Hutchinson 1948, Marshall 1954, Malkin and Schultz 1951, Williams 1957, Swan 1964, Schnyders et al 1965. In these measurements primary ionizing radiation is used to release electrons and positive ions.…”

Electron Mobility in Liquid Argon

“…This is the dependence reported by Malkin and Schultz (1951), but it is evident that the recent, more exhaustive work of Williams (1957) is correct on this point and therefore that kinetic theory is not applicable to the problem. This theory could in principle be extended to explain a fieldindependent velocity, by supposing a special dependence upon electron energy of the scattering cross section for the collision of electrons with argon atoms, but this is very artificial and unnecessary in view of the alternative explanation suggested here; in any case it leaves further serious objections, which will also be discussed briefly.…”