Positronium negative ion

A bound system containing a positron may be considered either as positronium bound to a positive ion or an atom or as a positron bound to the corresponding atom or negative ion. It is therefore appropriate to consider here all bound states containing positrons. Bound systems containing more than one positron, however, such as e+e+e (the anti-system of the positronium negative ion Ps ) and the positronium molecule Ps2, are considered in more detail in sections 8.1 and 8.2. 

Fig. 8.2. Apparatus used by Mills for studies of the positronium negative ion Gi is a pile-up-reducing grid, G2 is the Ps -forming carbon film and G3 is the acceleration grid. See the text for further details. Reprinted from Physical Review Letters 50, Mills, Measurement of the decay rate of the positronium negative ion, 671-674, copyright 1983 by the American Physical Society.

Ho, Y.K. (1984). Doubly excited states of positronium negative ions. Phys. 

Mills Jr., A.P. (1983b). Measurement of the decay rate of the positronium negative ion. Phys. Rev. Lett. 50 671-674. 

The HSCC equations have been solved for various Coulomb three-body processes, such as photoionization and photodetachment of two-electron systems and positronium negative ions [51, 105-111], electron or positron collisions [52, 112-115], ion-atom collisions [116-119], and muon-involving collision systems [103, 114, 120-125]. Figures 4.6, 4.7, 4.8, 4.9, and 4.10 are all due to HSCC calculations. Figure 4.12 illustrates the good agreement between the results of HSCC calculations [51] and the high-resolution photoionization experiment on helium [126]. See Ref. [127] for further detailed account of the comparison between the theory and experiment on QBSs of helium up to the threshold of He+(n = 9). 

A. Igarashi, I. Shimamura, Time-delay matrix analysis of resonances Application to the positronium negative ion, J. Phys. B At. Mol. Opt. Phys. 37 (2004) 4221. 

Systems in the collinear eZe configuration which have tori would be the antiproton-proton-antiproton (p-p-p) system, the positronium negative ion (Pr- e-e-e)), which corresponds to the case of Z= 1, = 1, and If these systems have bound states, we can see the effect of our finding in the Fourier transform of the density of states for the spectrum. For a positronium negative ion, the EBK quantization was done [34]. Stable antisymmetric orbits were obtained and were quantized to explain some part of the energy spectrum. As hyperbolic systems, H and He have been already analyzed in Refs. 11 and 17, respectively. Thus, Li+ is the next candidate. We might see the effect of the intermittency for this system in quantum defect as shown for helium [14]. 

Figure 14. Candidates of tori in the initial condition space for the ffee-faU prohlem positronium negative ion, Pr—. The painted region near the corner (x,y) = (1,0) represents the initial conditions with positive total energy.

The stability of three-body Coulomb systems is an old problem which has been treated in many particular cases [143-145] and several authors reviewed this problem [146,147]. For example, the He atom (ae e ) and H2 (ppa ) are stable systems, H (pe e ) has only one bound state [108], and the positronium negative ion Ps (e+e e ) has a bound state [148], while the positron-hydrogen system (e pe+) is unbound and the proton-electron-negative-muon pe i ) is an unstable system [149]. In this section, we show that all three-body ABA Coulomb systems undergo a first-order quantum phase transition from the stable phase of ABA to the unstable breakup phase of AB + A as their masses and charges varies. Using the FSS method, we calculate the transition line that... 

Figure 2, Experimental apparatus for detecting the positronium negative ion, Ps .

A field-free approach to polarizabilities of excited states has been designed to overcome the difficulties of the finite-field version of the Diffusion Monte Carlo method. It has been applied to the n = 2 hydrogen atom, whose hybrid orbitals partition into two nodal regions. The pseudostate method has been applied to calculate polarizabilities of the positronium negative ion. 

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