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 Letters

Experimental Determination of the Helium 2 P13–1 S01 Transition Rate

R. G. Dall, K. G. H. Baldwin, L. J. Byron, Andrew G. Truscott

Published Jan 15, 2008• 20 citations
Publisher

Abstract

We present the first experimental determination of the $2\text{ }^{3}P_{1}--1\text{ }^{1}S_{0}$ transition rate in helium and compare this measurement with theoretical quantum-electrodynamic predictions. The experiment exploits the very long ($\ensuremath{\sim}1\text{ }\text{ }\mathrm{\text{minute}}$) confinement times obtained for atoms magneto-optically trapped in an apparatus used to create a Bose-Einstein condensate of metastable ($2\text{ }^{3}S_{1}$) helium. The $2\text{ }^{3}P_{1}--1\text{ }^{1}S_{0}$ transition rate is measured directly from the decay rate of the cold atomic cloud following 1083 nm laser excitation from the $2\text{ }^{3}S_{1}$ to the $2\text{ }^{3}P_{1}$ state, and from accurate knowledge of the $2\text{ }^{3}P_{1}$ population. The value obtained is $177\ifmmode\pm\else\textpm\fi{}8\text{ }\text{ }{\mathrm{s}}^{\ensuremath{-}1}$, which agrees very well with theoretical predictions, and has an accuracy that compares favorably with measurements for the same transition in heliumlike ions higher in the isoelectronic sequence.

DOI
10.1103/physrevlett.100.023001

Related papers

Metastable Helium: A New Determination of the Longest Atomic Excited-State Lifetime

Sean S. Hodgman, R. G. Dall, L. J. Byron +3 more

Exited atoms may relax to the ground state by radiative decay, a process which is usually very fast (of order nanoseconds). However, quantum-mechanical selection rules can prevent such rapid decay, in which case these "metastable" states can have lifetimes of order seconds or longer. In this Letter, we determine experimentally the lifetime of the longest-lived neutral atomic state-the first excited state of helium (the 2(3)S1 metastable state)-to the highest accuracy yet measured. We use laser cooling and magnetic trapping to isolate a cloud of metastable helium (He*) atoms from their surrounding environment, and measure the decay rate to the ground 1(1)S0 state via extreme ultraviolet (XUV) photon emission. This is the first measurement using a virtually unperturbed ensemble of isolated helium atoms, and yields a value of 7870(510) seconds, in excellent agreement with the predictions of quantum electrodynamic theory.

Physical Review Letters•Jul 30, 2009•121 citations

Radiative Lifetime of the 2 S01 Metastable State of Helium

Robert S. Van Dyck, C. E. Johnson, Howard A. Shugart

A time-of-flight technique has been used to measure the radiative lifetime of the $2 ^{1}S_{0}$ state of helium. After passing from a cooled source, helium atoms are excited by a pulsed anti-parallel electron beam. The atomic beam then contains not only ground-state helium atoms but also metastable atoms in both the $2 ^{3}S_{1}$ and the $2 ^{1}S_{0}$ states. The metastable atoms are detected at two positions, 1.9 and 6.7 m from the electron gun, by Auger ejection of an electron from a copper target, the first of which is a 60% transmitting mesh. Ground-state helium atoms cannot cause an electron to be ejected and hence are not detected. The time-of-flight distribution for the metastable $2 ^{1}S_{0}$ state is separated from that of the $2 ^{3}S_{1}$ state by illuminating the beam with an rf-discharge helium lamp. The $2 ^{1}S_{0}$ state is quenched by resonant absorption of a 20 581 - \AA{}A photon, raising the atom to the $2 ^{1}P_{1}$ state, which then decays preferentially to the $^{1}S_{0}$ ground state; the $2 ^{3}S_{1}$ state remains unaffected because it is the ground state for the triplet system. The time-of-flight distribution for the $2 ^{1}S_{0}$ atoms is therefore obtained from the difference between the full beam and the quenched beam. A comparison of the number of $2 ^{1}S_{0}$ metastables within a given velocity interval at the two detectors determines the number which decay in flight and yields a value for the two-photon radiative lifetime. The value of the singlet lifetime for both ${\mathrm{He}}^{3}$ and ${\mathrm{He}}^{4}$ is 19.7 \ifmmode\pm\else\textpm\fi{} 1.0 msec, agreeing with the theoretical value of 19.5 msec, but disagreeing with the value 38 \ifmmode\pm\else\textpm\fi{} 8 msec measured by Pearl using a movable detector. The 1.0-msec error is an estimate of the remaining systematic errors in the experiment.

Physical Review A•Oct 1, 1971•99 citations

High-Precision Spectroscopy of the Forbidden 2 S13→2 P11 Transition in Quantum Degenerate Metastable Helium

Remy Notermans, W. Vassen

We have measured the forbidden $2\text{ }^{3}{S}_{1}\ensuremath{\rightarrow}2\text{ }^{1}{P}_{1}$ transition at 887 nm in a quantum degenerate gas of metastable $^{4}\mathrm{He}$ atoms confined in an optical dipole trap. The determined transition frequency is 338 133 594.4 (0.5) MHz, from which we obtain an ionization energy of the $2\text{ }^{1}{P}_{1}$ state of 814 709 148.6 (0.5) MHz. This ionization energy is in disagreement by $>3\ensuremath{\sigma}$ with the most accurate quantum electrodynamics calculations available. Our measurements also provide a new determination of the lifetime of the $2\text{ }^{1}{P}_{1}$ state of $0.551\text{ }(0.004{)}_{\text{stat}}\text{ }{(}_{\ensuremath{-}0.000}^{+0.013}{)}_{\text{syst}}\text{ }\text{ }\mathrm{ns}$, which is the most accurate determination to date and in excellent agreement with theory.

arXiv:1404.1759•Physical Review Letters•Jun 25, 2014•36 citations

The First Measurement of the $2^{3\!}S_1 - 2^{3\!}P / 3^{3\!}P$ Tune-Out Wavelength in He*

B. M. Henson

The workhorse of atomic physics, quantum electrodynamics, is one of the best-tested theories in physics. However recent discrepancies have shed doubt on its accuracy for complex atomic systems. To facilitate the development of the theory further we aim to measure transition dipole matrix elements of metastable helium (He*) (the ideal 3 body test-bed) to the highest accuracy thus far. We have undertaken a measurement of the `tune-out wavelength' which occurs when the contributions to the dynamic polarizability from all atomic transitions sum to zero; thus illuminating an atom with this wavelength of light then produces no net energy shift. This provides a strict constraint on the transition dipole matrix elements without the complication and inaccuracy of other methods. Using a novel atom-laser based technique we have made the first measurement of the tune-out wavelength in metastable helium between the $3^{3}P_{1,2,3}$ and $2^{3}P_{1,2,3}$ states at 413.07(2) nm which compares well with the predicted value [PhysRevA.88.052515] of 413.02(9) nm. We have additionally developed many of the methods necessary to improve this measurement to the 100 fm level of accuracy where it will form the most accurate determination of transition rate information ever made in He* and provide a stringent test for atomic QED simulations. We believe this measurement to be one of the most sensitive ever made of an optical dipole potential, able to detect changes in potentials of $\sim$200 pK and is widely applicable to other species and areas of atom optics.

arXiv:1708.08200•Aug 28, 2017•0 citations

The First Measurement of the $2^{3}S_{1} \rightarrow 3^{3}P - 2^{3}P$ Tune-Out Wavelength in He*

B. M. Henson

The workhorse of atomic physics, quantum electrodynamics, is one of the best-tested theories in physics. However recent discrepancies have shed doubt on its accuracy for complex atomic systems. To facilitate the development of the theory further we aim to measure transition dipole matrix elements of metastable helium (He*) (the ideal 3 body test-bed) to the highest accuracy thus far. We have undertaken a measurement of the `tune-out wavelength' which occurs when the contributions to the dynamic polarizability from all atomic transitions sum to zero; thus illuminating an atom with this wavelength of light then produces no net energy shift. This provides a strict constraint on the transition dipole matrix elements without the complication and inaccuracy of other methods. Using a novel atom-laser based technique we have made the first measurement of the tune-out wavelength in metastable helium between the $3^{3}P_{1,2,3}$ and $2^{3}P_{1,2,3}$ states at 413.07(2) nm which compares well with the predicted value\cite{Mitroy2013} of 413.02(9) nm. We have additionally developed many of the methods necessary to improve this measurement to the 100 fm level of accuracy where it will form the most accurate determination of transition rate information ever made in He* and provide a stringent test for atomic QED simulations. We believe this measurement to be one of the most sensitive ever made of an optical dipole potential, able to detect changes in potentials of $\sim$200 pK and is widely applicable to other species and areas of atom optics.

•Aug 28, 2017•0 citations

Quenching of the 2S01 Metastable State of Helium by an Electric Field

Charles E. Johnson

A time-of-flight technique has been used to measure the quenching of the $2^{1}S_{0}$ metastable state of helium by a static electric field. Neutral ground-state helium atoms effusing from a cooled source slit are immediately excited to the $2^{1}S_{0}$ and $2^{3}S_{1}$ metastable states by a pulse of antiparallel magnetically focused electrons. The metastable beam is collimated before passing through a uniform electric field region 0.5 m long and is then preferentially detected at the end of the time-of-flight region, 1.825 m from the electron gun. The time-of-flight distribution for the $2^{1}S_{0}$ state is separated from that of the $2^{3}S_{1}$ state by illuminating the beam before the electric field region with an rf-discharge helium lamp. The $2^{1}S_{0}$ state is quenched by resonant absorption of a 20 581-\AA{} photon, raising the atom to the $2^{1}P_{1}$ state, which then decays to the $^{1}S_{0}$ ground state; the $2^{3}S_{1}$ state remains unaffected because it is the ground state for the triplet system. The $2^{1}S_{0}$ time-of-flight distribution is therefore obtained from the difference between the full beam and the quenched beam. The number of $2^{1}S_{0}$ atoms arriving at the detector in specific velocity intervals with the electric field off is compared to the number with the field on to determine the quenching rate ($=k{E}^{2}$). The result for the quenching constant $k$ for both ${\mathrm{He}}^{3}$ and ${\mathrm{He}}^{4}$ with $E$ in kV/cm is $k=0.933\ifmmode\pm\else\textpm\fi{}0.005$; this value is in good agreement with theory and with an earlier less accurate experiment. The error in the present experiment arises from a 0.5% uncertainty in the effective length of the electric field region.

Physical Review A•Mar 1, 1973•10 citations
We present the first experimental determination of the 2 3P1−−1 1S02\text{ }^{3}P_{1}--1\text{ }^{1}S_{0}2 3P1​−−1 1S0​ transition rate in helium and compare this measurement with theoretical quantum-electrodynamic predictions. The experiment exploits the very long (\ensuremath∼1  minute\ensuremath{\sim}1\text{ }\text{ }\mathrm{\text{minute}}\ensuremath∼1  minute) confinement times obtained for atoms magneto-optically trapped in an apparatus used to create a Bose-Einstein condensate of metastable (2 3S12\text{ }^{3}S_{1}2 3S1​) helium. The 2 3P1−−1 1S02\text{ }^{3}P_{1}--1\text{ }^{1}S_{0}2 3P1​−−1 1S0​ transition rate is measured directly from the decay rate of the cold atomic cloud following 1083 nm laser excitation from the 2 3S12\text{ }^{3}S_{1}2 3S1​ to the 2 3P12\text{ }^{3}P_{1}2 3P1​ state, and from accurate knowledge of the 2 3P12\text{ }^{3}P_{1}2 3P1​ population. The value obtained is 177\ifmmode±\else\textpm\fi8  s\ensuremath−1177\ifmmode\pm\else\textpm\fi{}8\text{ }\text{ }{\mathrm{s}}^{\ensuremath{-}1}177\ifmmode±\else\textpm\fi8  s\ensuremath−1, which agrees very well with theoretical predictions, and has an accuracy that compares favorably with measurements for the same transition in heliumlike ions higher in the isoelectronic sequence.
Exited atoms may relax to the ground state by radiative decay, a process which is usually very fast (of order nanoseconds). However, quantum-mechanical selection rules can prevent such rapid decay, in which case these "metastable" states can have lifetimes of order seconds or longer. In this Letter, we determine experimentally the lifetime of the longest-lived neutral atomic state-the first excited state of helium (the 2(3)S1 metastable state)-to the highest accuracy yet measured. We use laser cooling and magnetic trapping to isolate a cloud of metastable helium (He*) atoms from their surrounding environment, and measure the decay rate to the ground 1(1)S0 state via extreme ultraviolet (XUV) photon emission. This is the first measurement using a virtually unperturbed ensemble of isolated helium atoms, and yields a value of 7870(510) seconds, in excellent agreement with the predictions of quantum electrodynamic theory.
A time-of-flight technique has been used to measure the radiative lifetime of the 21S02 ^{1}S_{0}21S0​ state of helium. After passing from a cooled source, helium atoms are excited by a pulsed anti-parallel electron beam. The atomic beam then contains not only ground-state helium atoms but also metastable atoms in both the 23S12 ^{3}S_{1}23S1​ and the 21S02 ^{1}S_{0}21S0​ states. The metastable atoms are detected at two positions, 1.9 and 6.7 m from the electron gun, by Auger ejection of an electron from a copper target, the first of which is a 60% transmitting mesh. Ground-state helium atoms cannot cause an electron to be ejected and hence are not detected. The time-of-flight distribution for the metastable 21S02 ^{1}S_{0}21S0​ state is separated from that of the 23S12 ^{3}S_{1}23S1​ state by illuminating the beam with an rf-discharge helium lamp. The 21S02 ^{1}S_{0}21S0​ state is quenched by resonant absorption of a 20 581 - \AA{}A photon, raising the atom to the 21P12 ^{1}P_{1}21P1​ state, which then decays preferentially to the 1S0^{1}S_{0}1S0​ ground state; the 23S12 ^{3}S_{1}23S1​ state remains unaffected because it is the ground state for the triplet system. The time-of-flight distribution for the 21S02 ^{1}S_{0}21S0​ atoms is therefore obtained from the difference between the full beam and the quenched beam. A comparison of the number of 21S02 ^{1}S_{0}21S0​ metastables within a given velocity interval at the two detectors determines the number which decay in flight and yields a value for the two-photon radiative lifetime. The value of the singlet lifetime for both He3{\mathrm{He}}^{3}He3 and He4{\mathrm{He}}^{4}He4 is 19.7 \ifmmode\pm\else\textpm\fi{} 1.0 msec, agreeing with the theoretical value of 19.5 msec, but disagreeing with the value 38 \ifmmode\pm\else\textpm\fi{} 8 msec measured by Pearl using a movable detector. The 1.0-msec error is an estimate of the remaining systematic errors in the experiment.
We have measured the forbidden $2\text{ }^{3}{S}_{1}\ensuremath{\rightarrow}2\text{ }^{1}{P}_{1}$ transition at 887 nm in a quantum degenerate gas of metastable 4He^{4}\mathrm{He}4He atoms confined in an optical dipole trap. The determined transition frequency is 338 133 594.4 (0.5) MHz, from which we obtain an ionization energy of the 2 1P12\text{ }^{1}{P}_{1}2 1P1​ state of 814 709 148.6 (0.5) MHz. This ionization energy is in disagreement by $>3\ensuremath{\sigma}$ with the most accurate quantum electrodynamics calculations available. Our measurements also provide a new determination of the lifetime of the 2 1P12\text{ }^{1}{P}_{1}2 1P1​ state of $0.551\text{ }(0.004{)}_{\text{stat}}\text{ }{(}_{\ensuremath{-}0.000}^{+0.013}{)}_{\text{syst}}\text{ }\text{ }\mathrm{ns}$, which is the most accurate determination to date and in excellent agreement with theory.
The First Measurement of the 23 ⁣S1−23 ⁣P/33 ⁣P2^{3\!}S_1 - 2^{3\!}P / 3^{3\!}P23S1​−23P/33P Tune-Out Wavelength in He*
The workhorse of atomic physics, quantum electrodynamics, is one of the best-tested theories in physics. However recent discrepancies have shed doubt on its accuracy for complex atomic systems. To facilitate the development of the theory further we aim to measure transition dipole matrix elements of metastable helium (He*) (the ideal 3 body test-bed) to the highest accuracy thus far. We have undertaken a measurement of the `tune-out wavelength' which occurs when the contributions to the dynamic polarizability from all atomic transitions sum to zero; thus illuminating an atom with this wavelength of light then produces no net energy shift. This provides a strict constraint on the transition dipole matrix elements without the complication and inaccuracy of other methods. Using a novel atom-laser based technique we have made the first measurement of the tune-out wavelength in metastable helium between the 33P1,2,33^{3}P_{1,2,3}33P1,2,3​ and 23P1,2,32^{3}P_{1,2,3}23P1,2,3​ states at 413.07(2) nm which compares well with the predicted value [PhysRevA.88.052515] of 413.02(9) nm. We have additionally developed many of the methods necessary to improve this measurement to the 100 fm level of accuracy where it will form the most accurate determination of transition rate information ever made in He* and provide a stringent test for atomic QED simulations. We believe this measurement to be one of the most sensitive ever made of an optical dipole potential, able to detect changes in potentials of $\sim$200 pK and is widely applicable to other species and areas of atom optics.
The First Measurement of the 23S1→33P−23P2^{3}S_{1} \rightarrow 3^{3}P - 2^{3}P23S1​→33P−23P Tune-Out Wavelength in He*
The workhorse of atomic physics, quantum electrodynamics, is one of the best-tested theories in physics. However recent discrepancies have shed doubt on its accuracy for complex atomic systems. To facilitate the development of the theory further we aim to measure transition dipole matrix elements of metastable helium (He*) (the ideal 3 body test-bed) to the highest accuracy thus far. We have undertaken a measurement of the `tune-out wavelength' which occurs when the contributions to the dynamic polarizability from all atomic transitions sum to zero; thus illuminating an atom with this wavelength of light then produces no net energy shift. This provides a strict constraint on the transition dipole matrix elements without the complication and inaccuracy of other methods. Using a novel atom-laser based technique we have made the first measurement of the tune-out wavelength in metastable helium between the 33P1,2,33^{3}P_{1,2,3}33P1,2,3​ and 23P1,2,32^{3}P_{1,2,3}23P1,2,3​ states at 413.07(2) nm which compares well with the predicted value\cite{Mitroy2013} of 413.02(9) nm. We have additionally developed many of the methods necessary to improve this measurement to the 100 fm level of accuracy where it will form the most accurate determination of transition rate information ever made in He* and provide a stringent test for atomic QED simulations. We believe this measurement to be one of the most sensitive ever made of an optical dipole potential, able to detect changes in potentials of $\sim$200 pK and is widely applicable to other species and areas of atom optics.
A time-of-flight technique has been used to measure the quenching of the 21S02^{1}S_{0}21S0​ metastable state of helium by a static electric field. Neutral ground-state helium atoms effusing from a cooled source slit are immediately excited to the 21S02^{1}S_{0}21S0​ and 23S12^{3}S_{1}23S1​ metastable states by a pulse of antiparallel magnetically focused electrons. The metastable beam is collimated before passing through a uniform electric field region 0.5 m long and is then preferentially detected at the end of the time-of-flight region, 1.825 m from the electron gun. The time-of-flight distribution for the 21S02^{1}S_{0}21S0​ state is separated from that of the 23S12^{3}S_{1}23S1​ state by illuminating the beam before the electric field region with an rf-discharge helium lamp. The 21S02^{1}S_{0}21S0​ state is quenched by resonant absorption of a 20 581-\AA{} photon, raising the atom to the 21P12^{1}P_{1}21P1​ state, which then decays to the 1S0^{1}S_{0}1S0​ ground state; the 23S12^{3}S_{1}23S1​ state remains unaffected because it is the ground state for the triplet system. The 21S02^{1}S_{0}21S0​ time-of-flight distribution is therefore obtained from the difference between the full beam and the quenched beam. The number of 21S02^{1}S_{0}21S0​ atoms arriving at the detector in specific velocity intervals with the electric field off is compared to the number with the field on to determine the quenching rate (=kE2=k{E}^{2}=kE2). The result for the quenching constant kkk for both He3{\mathrm{He}}^{3}He3 and He4{\mathrm{He}}^{4}He4 with EEE in kV/cm is $k=0.933\ifmmode\pm\else\textpm\fi{}0.005$; this value is in good agreement with theory and with an earlier less accurate experiment. The error in the present experiment arises from a 0.5% uncertainty in the effective length of the electric field region.