Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Measurement of the fluorescence decay rate of 2 P J 3 positronium

R. J. Daly, R. E. Sheldon, D. B. Cassidy

Published Aug 12, 2024• 4 citations
Publisher

Abstract

The fluorescence decay rate of 2 P J 3 positronium (Ps) atoms [ Γ fl ] has been experimentally determined using a Stark-mixing technique. Ground-state Ps atoms were optically excited in an electric field to states containing both 2 P J 3 and 2 3 S 1 components. The relative state populations were controlled via an applied mixing electric field, and a larger, pulsed, electric field was used to induce rapid quenching of the system after a fixed time delay. The dependence of the quenching signal on the mixing field strength was used to determine the relative and populations of the mixed states, whose decay rates are determined by the intrinsic self-annihilation and fluorescence decay rates. The measurements were compared to a trajectory simulation and Stark-mixing model, using the fluorescence decay rate as a free parameter. By finding the best agreement between the data and simulations we obtain Γ fl = 299 ± 25 µ s − 1 , which is consistent with the mean theoretical value of 313.343 ± 0.003 µ s − 1 . Published by the American Physical Society 2024

DOI
10.1103/physreva.110.022807

Related papers

Measurement of the annihilation decay rate of 2 3 S 1 positronium

R. E. Sheldon, Tamara J. Babij, Brendan Devlin-Hill +2 more

We report a measurement of the annihilation decay rate of positronium (Ps) atoms, . Ground state atoms optically excited to radiatively metastable states were quenched via Stark mixing by the application of a time-delayed electric field. Rapid radiative decay of the Stark mixed states to the ground state, followed by self-annihilation, was observed via the annihilation radiation time spectrum, and used to determine the number of excited state atoms remaining at different times, and hence the decay rate. We obtain , in broad agreement with the Zeeman-shifted theoretical value of .

Europhysics Letters (EPL)•Nov 3, 2020•3 citations

Controlling Positronium Annihilation with Electric Fields

A. Alonso, B. S. Cooper, Adam Deller +2 more

We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n=2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1^{3}S→2^{3}P→nS/nD), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2^{3}S_{1} component represents an efficient route to producing long-lived pure 2^{3}S_{1} atoms via single-photon excitation.

Physical Review Letters•Oct 27, 2015•19 citations

Production of 2S13 positronium atoms by single-photon excitation in an electric field

A. Alonso, S. D. Hogan, D. B. Cassidy

We report experiments in which positronium (Ps) atoms are produced in the $2\phantom{\rule{0.16em}{0ex}}^{3}S_{1}$ level by single-photon excitation from the ground state. To accomplish this, Stark-mixed $n=2$ states were optically excited in electric fields. By adiabatically switching off the electric field after laser excitation, some of the mixed states evolved into pure $2\phantom{\rule{0.16em}{0ex}}^{3}S_{1}$ levels, whose presence was detected via the time dependence of their annihilation $\ensuremath{\gamma}$ radiation. The observed $\ensuremath{\approx}4%$ production efficiency relative to that of Rydberg Ps states is consistent with a Monte Carlo simulation that takes into account the rate at which the electric fields were switched off.

Physical Review A•Mar 9, 2017•28 citations

Measurement of Rydberg positronium fluorescence lifetimes

Adam Deller, A. Alonso, B. S. Cooper +2 more

We report measurements of the fluorescence lifetimes of positronium (Ps) atoms with principal quantum numbers $n=10--19$. Ps atoms in Rydberg-Stark states were produced via a two-color two-step $1\phantom{\rule{0.16em}{0ex}}^{3}S\ensuremath{\rightarrow}2\phantom{\rule{0.16em}{0ex}}^{3}P\ensuremath{\rightarrow}n\phantom{\rule{0.16em}{0ex}}^{3}S/n\phantom{\rule{0.16em}{0ex}}^{3}D$ excitation scheme and subsequently detected after traveling 1.2 m. The measured time-of-flight distributions were used to determine the mean lifetimes of the Rydberg levels, yielding values ranging from $3\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$ to $26\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$. Our data are in accord with the expected radiative lifetimes of Rydberg-Stark states of Ps.

Physical Review A•Jun 29, 2016•26 citations

Two-photon Resonant Excitation Of Thallium In An Atomic Beam (multiphoton, Radiative Lifetimes).

John V. James

We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.

•Jan 1, 1986•0 citations

Spectroscopy and manipulation of positronium in excited states

A. Alonso

A Surko-type positron trap has been used to produce intense positron pulses, and thus a dilute positronium (Ps) gas in vacuum with an initial density of 10^7 cm-3. This gas was excited with lasers for a variety of experiments. n = 2 atoms were prepared using a single-photon excitation scheme (1S to 2P) in controlled electric and magnetic fields for studies of Stark and Zeeman effects, measurements of Ps cooling via Doppler spectroscopy, and for the produciton of ensembles of atoms in pure 2S states. The first measurements of Ps excitation to specific Rydberg-Stark states were performed via a two-color two-photon excitation scheme ( 1S to 2P to nS/nD). Ps atoms in low-field–seeking Rydberg Stark states were prepared at the entrance of an electrostatic quadrupole guide which was used to control the trajectories and velocity distributions of the Ps atoms. These advances, together with the results from numerical simulations, suggest that these methods could be used in to perform Stark deceleration and trapping of Rydberg Ps, high-precision Ps spectroscopy, and to create positron-atom bound states.

•Apr 28, 2018•0 citations
The fluorescence decay rate of 2 P J 3 positronium (Ps) atoms [ Γ fl ] has been experimentally determined using a Stark-mixing technique. Ground-state Ps atoms were optically excited in an electric field to states containing both 2 P J 3 and 2 3 S 1 components. The relative state populations were controlled via an applied mixing electric field, and a larger, pulsed, electric field was used to induce rapid quenching of the system after a fixed time delay. The dependence of the quenching signal on the mixing field strength was used to determine the relative and populations of the mixed states, whose decay rates are determined by the intrinsic self-annihilation and fluorescence decay rates. The measurements were compared to a trajectory simulation and Stark-mixing model, using the fluorescence decay rate as a free parameter. By finding the best agreement between the data and simulations we obtain Γ fl = 299 ± 25 µ s − 1 , which is consistent with the mean theoretical value of 313.343 ± 0.003 µ s − 1 . Published by the American Physical Society 2024
We report a measurement of the annihilation decay rate of positronium (Ps) atoms, . Ground state atoms optically excited to radiatively metastable states were quenched via Stark mixing by the application of a time-delayed electric field. Rapid radiative decay of the Stark mixed states to the ground state, followed by self-annihilation, was observed via the annihilation radiation time spectrum, and used to determine the number of excited state atoms remaining at different times, and hence the decay rate. We obtain , in broad agreement with the Zeeman-shifted theoretical value of .
We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n=2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1^{3}S→2^{3}P→nS/nD), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2^{3}S_{1} component represents an efficient route to producing long-lived pure 2^{3}S_{1} atoms via single-photon excitation.
We report experiments in which positronium (Ps) atoms are produced in the 23S12\phantom{\rule{0.16em}{0ex}}^{3}S_{1}23S1​ level by single-photon excitation from the ground state. To accomplish this, Stark-mixed n=2n=2n=2 states were optically excited in electric fields. By adiabatically switching off the electric field after laser excitation, some of the mixed states evolved into pure 23S12\phantom{\rule{0.16em}{0ex}}^{3}S_{1}23S1​ levels, whose presence was detected via the time dependence of their annihilation $\ensuremath{\gamma}$ radiation. The observed $\ensuremath{\approx}4%$ production efficiency relative to that of Rydberg Ps states is consistent with a Monte Carlo simulation that takes into account the rate at which the electric fields were switched off.
We report measurements of the fluorescence lifetimes of positronium (Ps) atoms with principal quantum numbers n=10−−19n=10--19n=10−−19. Ps atoms in Rydberg-Stark states were produced via a two-color two-step $1\phantom{\rule{0.16em}{0ex}}^{3}S\ensuremath{\rightarrow}2\phantom{\rule{0.16em}{0ex}}^{3}P\ensuremath{\rightarrow}n\phantom{\rule{0.16em}{0ex}}^{3}S/n\phantom{\rule{0.16em}{0ex}}^{3}D$ excitation scheme and subsequently detected after traveling 1.2 m. The measured time-of-flight distributions were used to determine the mean lifetimes of the Rydberg levels, yielding values ranging from $3\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$ to $26\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$. Our data are in accord with the expected radiative lifetimes of Rydberg-Stark states of Ps.
We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.
A Surko-type positron trap has been used to produce intense positron pulses, and thus a dilute positronium (Ps) gas in vacuum with an initial density of 10^7 cm-3. This gas was excited with lasers for a variety of experiments. n = 2 atoms were prepared using a single-photon excitation scheme (1S to 2P) in controlled electric and magnetic fields for studies of Stark and Zeeman effects, measurements of Ps cooling via Doppler spectroscopy, and for the produciton of ensembles of atoms in pure 2S states. The first measurements of Ps excitation to specific Rydberg-Stark states were performed via a two-color two-photon excitation scheme ( 1S to 2P to nS/nD). Ps atoms in low-field–seeking Rydberg Stark states were prepared at the entrance of an electrostatic quadrupole guide which was used to control the trajectories and velocity distributions of the Ps atoms. These advances, together with the results from numerical simulations, suggest that these methods could be used in to perform Stark deceleration and trapping of Rydberg Ps, high-precision Ps spectroscopy, and to create positron-atom bound states.