Measurement of Rydberg positronium fluorescence lifetimes

Deller, A.; Alonso, A. M.; Cooper, B. S.; Hogan, S. D.; Cassidy, D. B.

doi:10.1103/physreva.93.062513

Cited by 24 publications

(46 citation statements)

References 67 publications

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“…The fluorescence lifetimes of some pure states and 'circular' ( = n − 1) states of Ps with values of n in the range 10-20 are shown in Figure 2 [134]. As discussed in Section 3.2, pure states of Ps are generally not produced in experiments because the presence of even very weak external electric and magnetic fields can lead to strong mixing [176].…”

Section: The Atomic Structure Of Psmentioning

confidence: 99%

“…This means that single-shot methods were not appropriate, and single event detection was used instead, employing a relatively slow NaI scintillator based detector. The output of this detector was directly connected to an oscilloscope, and an algorithm used (off-line) to register annihilation events based on pulse height and width criteria that are optimized to reduce background events [134]. This methodology is similar to standard positron annihilation spectroscopy (e.g.…”

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

“…Ps atoms emitted from the target are excited to long-lived states and some fraction of them travel 1.2 m along the straight flight path (green dashes) to annihilate near the NaI+PMT gamma-ray detector. From reference [134]. not expected to have any significant impact on the Ps atoms).…”

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

“…Thus, the mean lifetime of 2 3 P J Ps states is 3.2 ns, compared to 1.6 ns for hydrogen. More generally, the fluorescence lifetime, τ n , of a pure-state [134].…”

Section: The Atomic Structure Of Psmentioning

confidence: 99%

“…The configuration shown in Figure 21 was used to measure Ps lifetimes by detecting Rydberg Ps atoms 1.2 m away from the Ps source [134]. Ps atoms typically have speeds on the order of 10 7 cm s −1 (see Sect.…”

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

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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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Section: The Atomic Structure Of Psmentioning

confidence: 99%

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

“…Thus, the mean lifetime of 2 3 P J Ps states is 3.2 ns, compared to 1.6 ns for hydrogen. More generally, the fluorescence lifetime, τ n , of a pure-state [134].…”

Section: The Atomic Structure Of Psmentioning

confidence: 99%

Section: Fluorescence Decay Of Rydberg Atomsmentioning

confidence: 99%

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Experimental progress in positronium laser physics

2018

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SSPALS: A tool for studying positronium

Deller

2019

Nuclear Instruments and Methods in Physics Research Section A:

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Single-shot positron annihilation lifetime spectroscopy (SSPALS) is an extremely useful tool for experiments involving the positronium atom (Ps). I examine some of the methods that are typically employed to analyze lifetime spectra, and use a Monte-Carlo simulation to explore the advantages and limitations these have in laser spectroscopy experiments, such as resonance-enhanced multiphoton ionization (REMPI) or the production of Rydberg Ps.Positronium (Ps) [1] is the bound state of an electron and a positron. In vacuum, the components of the particle-antiparticle pair will ultimately annihilate with each other. The mean lifetime against self-annihilation is 125 ps for the n = 1 singlet spin state (1 1 S 0 , para-Ps) [2,3] or 142 ns for the n = 1 triplet spin states (1 3 S 1 , ortho-Ps) [4,5]. Annihilation of p-Ps usually results in two 511 keV gamma-ray photons, whereas o-Ps predominately decays into three with a combined energy of 1.022 MeV [6]. A scintillator coupled to a photomultiplier tube (PMT) can be used to efficiently detect gamma rays with subns timing resolution [7]. This facilitates precision positron annihilation lifetime spectroscopy (PALS) [8, 9] -a simple but powerful technique that was instrumental in the discovery of positronium by Deutsch in 1951 [10].The gross atomic structure of Ps [11] can be described by the Bohr model for hydrogen but with a reduced mass of µ Ps = m e /2; the corresponding energy levels are then given by E n = −6.8/n 2 (eV). Optical excitation from the ground state can be achieved using a pulsed laser synchronized to a time-bunched Ps source (∆t 10 ns) [12][13][14][15][16][17][18]. The annihilation and fluorescence decay rates of the excited states range widely [19,20] and laser excitation to these can have a marked effect on the overall lifetime. But to measure a PALS spectrum each annihilation event must be resolvable in the time domain, which is generally not possible with ns Ps sources. In this case, single-shot positron annihilation lifetime spectroscopy (SSPALS) [21] can be implemented instead. Here, the output of a fast gamma-ray detector constitutes the lifetime spectrum. This is a valid approximation if the Ps formation time and the decay time of the detector are both sufficiently short. PbWO 4 has a scintillation decay time of κ ∼ 10 ns, which is well suited to resolving o-Ps decay (τ = 142 ns). The Cerenkov radiator PbF 2 can be used to improve timing resolution [22] but Email address: a.deller@ucl.ac.uk (Adam Deller) it has a lower light output. For some applications, a slower material with a higher light output, such as LYSO (κ ∼ 40 ns), might be chosen to improve detection efficiency and the signalto-noise ratio [23].Pulsed Ps sources, with time widths of a few ns, can be obtained by implanting time-focused positron beams [24,25] into Ps-converter materials, such as mesoporous SiO 2 [26]. The interconnected network of pores provides a path to vacuum along which Ps atoms cool via inelastic collisions [14,27]. The overall efficiency for emission of o-Ps from...

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