The formation of positronium in molecular substances

Tao, S. J.

doi:10.1007/bf00929530

Cited by 93 publications

(37 citation statements)

References 29 publications

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“…Therefore, in the present blend, the contribution of the -C=O group of EVA to Ps inhibition is not as strong as observed for the conjugated group [1]. Second, as the PVC content in the blend increases, the intensity of the peak height decreases indicating that positron trapping also decreases and the chlorine in the PVC inhibits the Ps formation [20,22], as evidenced by the observed decreased o-Ps intensity (I 3 ), as shown in Table I, in complete agreement with earlier works [5,6,8,[31][32][33].…”

Section: -3supporting

confidence: 89%

Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

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The present work studied the role of the polar group unconjugated oxygen on the inhibition of positronium (Ps) formation in two binary blends made from a set of chosen constituent polymers with polar and weakly polar groups (nonpolar). The polymer blend samples of PVC-EVA and PVC-SAN were investigated by coincidence Doppler broadening and positron lifetime techniques. The strong polar acetate group in the EVA contributed to positron annihilation with electrons of unconjugated oxygen (-C + =O − ) as revealed by the momentum distribution curves peaking around 17 P L (10 −3 m 0 c). The ortho-Ps intensity indicated the unconjugated oxygen shows about a 28% Ps reduction even in the presence of a strong Ps inhibiting halogen (Cl − ). In contrast, this effect was not seen in the PVC-SAN blends since SAN contains a weakly polar (nonpolar) acrylonitrile group (C≡N). Our results indicate the chlorine of PVC in the blends is a major contributor to Ps inhibition through the formation of a (Cl − -e +) bound state but the unconjugated oxygen in EVA of the PVC-EVA blend also plays a similar, but lesser, role.

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Section: -3supporting

confidence: 89%

Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

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“…Fast positrons rapidly thermalize in the bulk material, where they are able to form Ps atoms [244]. The large internal surface areas and open volumes of these materials can result in the efficient production of Ps atoms with lifetimes close to the vacuum lifetime.…”

Section: Ps Productionmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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Abstract. The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥10 6 ) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 10 7 cm −3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.

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“…The Onsager radius r c involved in this expression is 577 Å / ε at room temperature. Expression (2) resembles the equation derived by Tao [15], who also attracted the Onsager formula to estimate the Ps formation probability. ( 1 ) ε ( X AA ) as calculated by simplified Onsager equation (7), ( 2 ) ε ( X AA , t Ps ) as calculated by Eq.…”

Section: Recombination Mechanism Of Positronium Formationmentioning

confidence: 93%

Effect of dielectric screening on positronium formation in acetone-acetic acid polar solvent blends

2005

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The influence of polarization of a medium in the vicinity of the positron-electron pair produced at the end of a fast-positron track on the formation of positronium (Ps) was considered. Weakening interaction between the positron and electron, polarization leads to a decrease in the Ps formation probability. The transience of Ps formation requires that the time delay of medium polarization should be taken into account. In turn, the magnitude of dielectric screening in acetone-acetic acid mixtures strongly depends on the ratio between the amounts of polar monomeric acetic acid and its nonpolar dimer. Sequentially taking account of these effects, it is possible to explain both the complex behavior of the Ps yield and the dependence of dielectric permittivity of the mixture on its composition.

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The formation of positronium in molecular substances

Cited by 93 publications

References 29 publications

Influence of polar groups in binary polymer blends on positronium formation

Influence of polar groups in binary polymer blends on positronium formation

Experimental progress in positronium laser physics

Effect of dielectric screening on positronium formation in acetone-acetic acid polar solvent blends

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