Effect of the energy loss process on the annihilation of orthopositronium in silica aerogel

Chang, Tsaiyu; Xu, Min; Zeng, Xiaopeng

doi:10.1016/0375-9601(87)90458-0

Cited by 69 publications

(41 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the intrinsic energy resolution of the technique is much better than this; it is possible to deconvolve the annihilation radiation spectra and infer Ps energies on the meV scale, in much the same way as one might split an atomic resonance lineshape (e.g. [389] A recent advance in this area takes advantage of the fact that, during o-Ps-Xe collisions, a spin conversion process can occur via spin-orbit interactions, resulting in a twophoton decay [370,394]. This interaction occurs via p-wave scattering and is therefore highly energy dependent, which means that measurements of the two-photon annihilation rate can be used to measure the Ps energy as a function of time with high sensitivity [395,396].…”

Section: Doppler and Time-of-flight Spectroscopymentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

View full text Add to dashboard Cite

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.

show abstract

Section: Doppler and Time-of-flight Spectroscopymentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

View full text Add to dashboard Cite

show abstract

“…Then the energy loss of the Ps becomes much slower [12,13,14]. This leads to the time dependence of the collisional quenching rates, resulting in time dependence of the total annihilation rate λ oPs and subtle and complicated shape of the o-Ps time spectrum.…”

Section: Methodsmentioning

confidence: 99%

Pickoff and spin conversion of orthopositronium in oxygen

et al. 2001

View full text Add to dashboard Cite

The quenching processes of the thermalized ortho-positronium(o-Ps) on an oxygen molecule have been studied by the positron annihilation age-momentum correlation techinique(AMOC). The Doppler broadening spectrum of the 511 keV γ-rays from the 2γ annihilation of o-Ps in O2 has been measured as a function of the o-Ps age. The rate of the quenching, consisting of the pickoff and the spin-conversion, is estimated from the positron lifetime spectrum. The ratio of the pickoff quenching rate to the spin-conversion rate is deduced from the Doppler broadening of the 511 keV γ-rays from the annihilation of the o-Ps. The pickoff parameter 1 Z eff , the effective number of the electrons per molecule which contribute to the pickoff quenching, for O2 is determined to be 0.6 ± 0.4. The cross-section for the elastic spin-conversion quenching is determined to be (1.16 ± 0.01) × 10 −19 cm 2 .

show abstract

“…the measured o-Ps lifetime becomes independent from the choice of the initial point in the analysis of the long-lived part of the spectrum). The experimental data for ultrafine silica powders give the time to full thermalization rather long: 10 ns [200], 20 ns [201]; in the case of aerosil [202] up to 50 ns.…”

Section: The Role Of Excited Statesmentioning

confidence: 99%