Ramsauer minimum

Sowada and Warman (1982) have described a dc conductivity method for Ar gas at 295 K and 45 atm. Following a 20-ns pulse of irradiation, the conductivity rises to a peak at -50 ns, due to the Ramsauer effect, before settling to a plateau, which is ascribed to thermal conductivity since the collecting field is very low. Since there is little electron loss, the conductivity profile is proportional to the mobility profile this in turn can be considered a kind of image of collision frequency as a function of electron energy. The time to reach the conductivity plateau, -150 ns, is the measure of thermalization time in the present case. At a density of -9 X 1021 cm-3, the conductivity maximum vanishes, indicating the disappearance of the Ramsauer minimum according to Sowada and Warman. 

The reason for the large difference between the values of A for positrons and electrons at an energy of 2 eV is that for positrons the s-wave phase shift passes through zero at the Ramsauer minimum and the dominant contribution to the cross section therefore comes from the p-wave, which is quite strongly peaked in the forward and backward directions. In contrast, there is no Ramsauer minimum in electron-helium scattering, and the isotropic s-wave contribution to aT is dominant at this energy. 

This equation becomes important if, for example, one considers scattering of 1 eV electrons on xenon in a deflection analyser with 0 = 45°. From Fig. 4.38 one would conclude that scattering effects are small because the scattering cross section is small (Ramsauer minimum), but the reduction of kinetic energies towards the turning point increases [Pg.147]

An important and unique study using PR-TRMC was reported by Shimamori et al. in 992 In this work they made use of the extremely low thermalization efficiency of xenon which is caused by the Ramsauer minimum effect. This allowed them to increase the average equilibrium electron energy by applying even relatively low microwave power levels. In this way, detailed information was obtained on the energy dependence of the attachment coefficient for a variety of halogen-containing compounds. 

Fig. 2. Scattering cross sections for pt with a hydrogen isotope nuclei from Refs. [12,18], showing the Ramsauer-Townsend minimum at around 10 eV for pt+p pt(F) +t cross sections plotted include both elastic and spin exchange reactions, where pt(0) is the singlet state and pt( 1) is the triplet state...

Is there a Ramsauer-Townsend minimum in the electron scattering cross section for liquids with a < 0 (V < OeV) and the heavier liquefied... 

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