Optical Spectroscopy of Molecular Positronium

Cassidy, D. B.; Hisakado, T. H.; Tom, H. W. K.; Mills, A. P.

doi:10.1103/physrevlett.108.133402

Cited by 67 publications

(59 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The efficiency with which Ps atoms can be transferred from n = 2 to Rydberg levels has been observed ot be very high (≥90%) [118]. This was attributed to mixing of the Rydberg levels that inhibits stimulated emission back to n = 2, thereby locking the atoms in the excited states.…”

Section: Excitation Of Rydberg Statesmentioning

confidence: 88%

“…The possibility of improving this measurement so that it becomes competitive with the precision (ppm) microwave measurements [81,313,322,376,377] has been discussed in reference [119]. In principle ppm level measurements are thought to be possible with many months of data collection, but only by implementing several very significant improvements, including utilizing a much more intense positron source.…”

Section: Stark and Zeeman Effects In N = 2 Psmentioning

confidence: 99%

“…As discussed elsewhere [328], both of these materials can be used for SSPALS measurements. PWO is less efficient in terms of light production (a few percent of NaI) [359] and has a decay time of around 10 ns, which makes it well suited for very high intensity pulses, as are required for Ps-Ps scattering or Ps 2 formation experiments [119,[360][361][362]. LYSO has a high density (8 g cm −3 ), a high light output (∼75% of NaI), and a decay time of ≈40 ns.…”

Section: Optical Excitation Of Positronium Atomsmentioning

confidence: 99%

See 2 more Smart Citations

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: Excitation Of Rydberg Statesmentioning

confidence: 88%

Section: Stark and Zeeman Effects In N = 2 Psmentioning

confidence: 99%

Section: Optical Excitation Of Positronium Atomsmentioning

confidence: 99%

See 1 more Smart Citation

Experimental progress in positronium laser physics

2018

View full text Add to dashboard Cite

show abstract

“…While different experimental approaches to study positron binding to atoms have been proposed, e.g., by measuring resonant positron-atom annihilation [10,11] or by laser-assisted photorecombination [12], the existence of excited states is of crucial importance for detecting positron-atom complexes as it should allow spectroscopic measurements. Just recently such an approach has been used by Cassidy et al [13] to confirm the production of a positronium molecule (Ps 2 ). The technique employed in Ref.…”

mentioning

confidence: 99%

“…The technique employed in Ref. [13] was based on observing small yet detectable changes in the annihilation yield of dense Ps over a narrow range of wavelengths corresponding to a transition between the ground and excited states of Ps 2 . The existence of a bound excited state of Ps 2 , in turn, had been previously predicted by numerical calculations [14].…”

mentioning

confidence: 99%

Excited States of Positronic Lithium and Beryllium

Bubin

Prezhdo

2013

Phys. Rev. Lett.

View full text Add to dashboard Cite

Using a variational method with an explicitly correlated Gaussian basis, we study the e þ -Li and e þ -Be complexes in the ground and lowest excited states with higher spin multiplicity. Our calculations provide rigorous theoretical confirmation that a positron can be attached to the excited states: 1s2s2p 4 P o and 1s 2 2s2p 3 P o for e þ -Li and e þ -Be, respectively. The result is particularly notable for the e þ -Be complex, as the excited 3 P o state lies below the autoionization threshold. We report accurate binding energies, annihilation rates and structural properties of these positron-atom systems. The existence of the ground and metastable excited states with bound positron opens up a new route to the presently lacking experimental verification of stability of a positron binding to any neutral atom. DOI: 10.1103/PhysRevLett.111.193401 PACS numbers: 36.10.Àk, 31.15.ac, 31.15.xt Understanding the mechanisms of the interaction of low energy positrons with matter is one of the main tasks of positron physics and chemistry. In particular, of great interest is the question whether atoms and molecules can capture positrons and form bound states stable against dissociation [1][2][3][4][5][6][7][8][9]. Since 1997, when the first conclusive and rigorous theoretical confirmation of a possibility of attaching a positron to a neutral lithium was given [1], there have been a number of investigations claiming the dynamical stability of positron-atom complexes. At present, at least a dozen atoms are believed to be capable of binding a positron. In contrast, on the experimental side no evidence has been collected as of yet to demonstrate the existence of positronic atoms. While different experimental approaches to study positron binding to atoms have been proposed, e.g., by measuring resonant positron-atom annihilation [10,11] or by laser-assisted photorecombination [12], the existence of excited states is of crucial importance for detecting positron-atom complexes as it should allow spectroscopic measurements. Just recently such an approach has been used by Cassidy et al. [13] to confirm the production of a positronium molecule (Ps 2 ). The technique employed in Ref.[13] was based on observing small yet detectable changes in the annihilation yield of dense Ps over a narrow range of wavelengths corresponding to a transition between the ground and excited states of Ps 2 . The existence of a bound excited state of Ps 2 , in turn, had been previously predicted by numerical calculations [14].Only a handful of theoretical studies so far have dealt with the investigation of excited states of positronic atoms. The simplest multielectron atom, helium, has been known to attach a positron in its 1s2s 3 S state for more than a decade [15] (here and below the term symbol refers to electrons only). Recently, it has also been shown that positron attachment is possible in three doubly excited states [16][17][18]. Nevertheless, in its ground singlet state He does not form a bound positron-atom complex. There was also an indication...

show abstract

Binding Matter with Antimatter: The Covalent Positron Bond

2018

View full text Add to dashboard Cite

We report sufficient theoretical evidence of the energy stability of the e+⋅H22− molecule, formed by two H− anions and one positron. Analysis of the electronic and positronic densities of the latter compound undoubtedly points out the formation of a positronic covalent bond between the otherwise repelling hydride anions. The lower limit for the bonding energy of the e+⋅H22− molecule is 74 kJ mol−1 (0.77 eV), accounting for the zero‐point vibrational correction. The formation of a non electronic covalent bond is fundamentally distinct from positron attachment to stable molecules, as the latter process is characterized by a positron affinity, analogous to the electron affinity.

show abstract

Optical Spectroscopy of Molecular Positronium

Cited by 67 publications

References 31 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Excited States of Positronic Lithium and Beryllium

Binding Matter with Antimatter: The Covalent Positron Bond

Contact Info

Product

Resources

About