Electric Field Amplification of He II Luminescence Below 0.8°K
The passage of alpha particles through liquid He II produces luminescence, part of which derives from metastable atomic or molecular systems with lifetimes which become increasingly longer as the temperature is reduced below T λ . 1 This is caused by the increased diffusion coefficient of the metastables (∼ e △/kT ) which enables them to escape prompt collision-induced destruction near the alpha-particle “track,” where a high density of collision partners is initially available. The resulting delay of their radiative destruction causes the intensity of scintillation pulses from the fluid (radiation emitted within approximately 10−6 sec of alpha emission) to decrease below about 1.7°K to a constant value attained at about 0.8°K. At this temperature and below all of the metastables escape prompt destruction. The, T dependence can be accounted for quantitatively by calculating the fraction of metastables which undergo prompt radiative destruction,2 assuming the diffusion coefficients of both metastables and their collision partners (ions or other metastables) to be porportional to e △/kT .
KeywordsVortex Ring Alpha Particle Pulse Time Pulse Intensity Alpha Emission
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- 4.L. Bruschi, P. Mazzoldi, and M. Santini, Phys. Rev. Lett. 21 1738 (1968), and references cited therein.Google Scholar