Ortho-positronium localization in pores of Vycor glass at low temperature

Zaleski, R.

doi:10.1088/1742-6596/443/1/012062

Cited by 6 publications

(4 citation statements)

References 31 publications

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“…Particularly, at low temperature, the (T) relation does not follow the dependence expected by the ETE model for numerous samples [42][43][44][45]. Attempts to explain this behavior as thermal expansion, adsorption of gas remnants on pore walls, or o-Ps localization [46] were taken. However, its origin is unknown in many cases.…”

Section: Applicability Of Ppmentioning

confidence: 98%

Principles of positron porosimetry

Zaleski

2015

Nukleonika

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Abstract. The paper deals with positron porosimetry (PP), which is based on positron annihilation lifetime spectroscopy (PALS). The numerical analysis of positron lifetime spectra for PP is more demanding than in most of other applications of PALS. The resulting intensity distributions of ortho-positronium (o-Ps) lifetimes are interpreted in terms of the extended Tao-Eldrup (ETE) model, which provides the dependence between the o-Ps lifetime and pore size. Additionally, the relation between the intensity of an o-Ps component and the pore volume allows obtaining pore size distribution (PSD). The value of the empirical parameter , which is dependent on material, can be estimated from the temperature dependence of an o-Ps lifetime. The most unique feature of PP among other techniques that allow determination of PSDs is its ability to perform measurements in almost any conditions. This makes this method suitable for various in situ studies. In this review article, both the capabilities and the limitations of PP are discussed. The methods to overcome some of the limitations are presented.

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Section: Applicability Of Ppmentioning

confidence: 98%

Principles of positron porosimetry

Zaleski

2015

Nukleonika

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“…Remarkably, however, it has been found that the nature of the material does not have a significant effect on the pickoff decay rate [14], which means that generic models that focus on geometric properties can describe Ps decay rates in a wide range of materials. This type of model, known as the Tao-Eldrup (TE) model [15,16], has well-documented limitations [17][18][19] but, with various modifications, can successfully correlate Ps lifetimes directly with free volumes [20][21][22][23][24][25]. This approach implicitly assumes that interactions with internal surfaces do not affect the Ps decay rate via mechanisms other than pickoff annihilation, e.g., via spin exchanging interactions with paramagnetic centers [26,27] or chemical quenching [28,29].…”

Section: Introductionmentioning

confidence: 99%

Annihilation of positronium atoms confined in mesoporous and macroporous SiO2 films

et al. 2018

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We report experiments in which positronium (Ps) atoms were created in thin, porous silica films containing isolated voids with diameters ranging from 5 to 75 nm. Ps lifetimes in the pore structures were measured directly via time-delayed laser excitation of 1 3 S 1 → 2 3 P J transitions. In a film containing 5-nm pores Ps was predominantly emitted into vacuum, with a small component of confined Ps with a lifetime of 75 ns also observed. In films with larger pores Ps atoms were not emitted into vacuum except from the film surface, and confined Ps lifetimes of ≈90 ns were measured with no dependence on the pore size. However, for such large pores, extended Tao-Eldrup (ETE)-type models predict Ps lifetimes close to the 142-ns vacuum value. Moreover, 1 3 S 1 → 2 3 P J excitation of Ps atoms inside the pores was found to result in annihilation and exhibited an extremely broad (≈10 THz) linewidth. We attribute these observations to a process in which nonthermal Ps atoms in the isolated voids become temporarily trapped in a series of surface states that dissociate following excitation. The occurrence of this mechanism is not necessarily apparent from ground-state Ps decay rates without some prior knowledge of the sample structure, and it precludes the application of ETE-type models as they do not take into account surface interactions other than pickoff annihilation.

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“…The initial positronium kinetic energy quickly decreases via inelastic and elastic collisions [15,16]. Various theoretical and experimental studies revealed that the energy transfer from positronium to porous materials is quite efficient [3,4,[17][18][19][20]. The implanted o-Ps reaches thermal equilibrium before to the annihilation time [21].…”

Section: Introductionmentioning

confidence: 99%

“…In order to achieve an optimized production of positronium, new porus silica materials have been recently tested [19,23] and new experimental techniques have been considered [24]. Moreover, a subject of active investigation concerns the acceleration of the positronium thermalization by the injection of remoderator gases like Ar [25,26] or Xe [27,28] at high pressure inside the porous materials.…”

Section: Introductionmentioning

confidence: 99%

Bose–Einstein condensation of positronium: modification of thes-wave scattering length below to the critical temperature

Morandi¹,

Hervieux²,

Manfredi³

2016

J. Phys. B: At. Mol. Opt. Phys.

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The production of a Bose-Einstein condensate made of positronium may be feasible in the near future. Below the condensation temperature, the positronium collision process is modified by the presence of the condensate. This makes the theoretical description of the positronium kinetics at low temperature challenging. Based on the quasi-particle Bogoliubov theory, we describe the many-body particle-particle collision in a simple manner. We find that, in a good approximation, the full positroniumpositronium interaction can be described by an effective scattering length. Our results are general and apply to different species of bosons. The correction to the bare scattering length is expressed in terms of a single dimensionless parameter that completely characterizes the condensate. IPCMS Strasbourg

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Ortho-positronium localization in pores of Vycor glass at low temperature

Cited by 6 publications

References 31 publications

Principles of positron porosimetry

Principles of positron porosimetry

Annihilation of positronium atoms confined in mesoporous and macroporous SiO2 films

Bose–Einstein condensation of positronium: modification of thes-wave scattering length below to the critical temperature

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