No abstract

carried out MPHF and optimized-spin-function studies on Li( 2 S) ^nw*,> 1 J L. 1 r , D = 9.3 Amagats E / D = 0.0 J 2.74nsec/Channel \

No abstract

Several groups 1 " 8 have recently observed a nonexponential form for the direct component of positron annihilation in the noble gases. In particular, the annihilation spectrum [ Fig. 2(a)] possesses a marked shoulder followed by an exponential decay. This effect has been interpreted 1 "" 3 in terms of a velocity dependence of the positron annihilation rate, implying that the cross section for direct annihilation rises more rapidly at low positron energies than does the simple inverse velocity dependence.The results presented in this paper indicate the velocity dependence in a more direct way by displaying the effect of an applied electric field on the lifetime characterizing the exponential portion of the annihilation spectrum. The observed annihilation rate is thus the velocitydependent annihilation rate averaged over the positron equilibrium velocity distribution determined by the strength of the applied electric field. The effect of such fields on the energy-distribution functions of electrons in gases has been the subject of extensive investigation, 4 * 5 whereas the only consideration of such effects for the case of positrons in gases is contained in the work of Marder et al., 8 which was concerned with an investigation of the effect of applied electric fields on the fraction of positrons forming positronium.The experimental work described in this paper was performed using the chamber illustrated in Fig. 1. It is an aluminum chamber demon VOLTAGE CONNECTOR COPPER RINGS

No abstract