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

Journal of Physics Conference Series

The effect of the spin-orbit and Stark mixing on photon yield spectra of photoexcited helium

A. Mihelič, M. Žitnik

Published Nov 5, 2012• 0 citations
Publisher

Abstract

Photon yields resulting from radiative cascades of photoexcited helium singly and doubly excited states in a dc electric field are presented. The combined effect of the spin-orbit and the field-induced mixing on the yields are examined.
DOI
10.1088/1742-6596/388/2/022047

Related papers

Combined effect of Stark and singlet-triplet mixing on photon-yield spectra of singly excited helium

A. Mihelič, M. Žitnik, Kevin Charles Prince +2 more

We present a theoretical framework for the calculation of photon-yield spectra from radiative-cascade decays of photoexcited helium atoms in a static electric field for incident photon energies below the first ($N=1$) ionization threshold. The present theory takes full account of the singlet-triplet mixing among the singly excited states with principal quantum numbers $n\ensuremath{\lesssim}10$. The model predicts the enhancement of transition probabilities to triplet final states due to the field-induced mixing. In particular, for a field strength of 9.17 kV/cm, polarization of incident photons perpendicular to the field, and a 4 meV broad excitation function tuned to the $1s6p\phantom{\rule{0.16em}{0ex}}{}^{1}\phantom{\rule{-0.16em}{0ex}}P$ states, the $1s6\ensuremath{\ell}\ensuremath{\rightarrow}1s2p\phantom{\rule{0.16em}{0ex}}{}^{3}\phantom{\rule{-0.16em}{0ex}}P$ and $1s5\ensuremath{\ell}\ensuremath{\rightarrow}1s2p\phantom{\rule{0.16em}{0ex}}{}^{3}\phantom{\rule{-0.16em}{0ex}}P$ emitted photon yields are predicted to be about 70 times and 20 times lower, respectively, than the photon yields for transitions to the corresponding singlet final states.

Physical Review A•Feb 22, 2012•3 citations

Experimental confirmation of photon-induced spin-flip transitions in helium via triplet metastable yield spectra

Jan‐Erik Rubensson, Angelica Moise, A. Mihelič +3 more

Doubly excited states below the $N=2$ ionization threshold are populated by exciting helium atoms in a supersonic beam with monochromatized synchrotron radiation. The fluorescence decay of these states triggers a radiative cascade back to the ground state with large probability to populate long lived singlet and triplet helium metastable states. The yield of metastables is measured using a multichannel plate detector after the beam has passed a singlet-quenching discharge lamp. The variation of the yield observed with the lamp switched on or off is related to the triplet-singlet mixing of the doubly excited states.

Physical Review A•Jun 25, 2010•7 citations

Quenching of the 2pnd Po1 doubly excited states of helium by a dc electric field

K. Bučar, M. Žitnik, A. Mihelič +6 more

The fluorescence yield quenching of low-lying doubly excited $2pnd$ $^{1}{P}^{o}$ states is observed to depend strongly on a dc electric field strength and its orientation with respect to the polarization of the incoming photon beam. The reduction of the yield accompanied by the lifetime shortening is attributed to the Stark mixing with the neighboring $2sns$ $^{1}{S}^{e}$ states, which redirects the $2pnd$ $^{1}{P}^{o}$ decay to the prompt autoionization channel. For $n\ensuremath{\ge}4$, the lifetimes decrease from several hundred picoseconds down to several tens of picoseconds when an electric field in the kV/cm range is applied parallel to the photon probe polarization. Practically no lifetime change is observed for polarization perpendicular to the electric field direction. The results of the complex-scaling calculations are in a good agreement with the experimental data.

Physical Review A•Jul 11, 2014•1 citation

Rydberg states of helium in electric and magnetic fields of arbitrary relative orientation

Ondřej Tkáč, Matija Žeško, Josef A. Agner +2 more

A spectroscopic study of Rydberg states of helium (n = 30 and 45) in magnetic, electric and combined magnetic and electric fields with arbitrary relative orientations of the field vectors is presented. The emphasis is on two special cases where (i) the diamagnetic term is negligible and both paramagnetic Zeeman and Stark effects are linear (n = 30, B ≤ 120 mT and F = 0-78 V cm⁻¹), and (ii) the diamagnetic term is dominant and the Stark effect is linear (n = 45, B = 277 mT and F = 0-8 V cm⁻¹). Both cases correspond to regimes where the interactions induced by the electric and magnetic fields are much weaker than the Coulomb interaction, but much stronger than the spin-orbit interaction. The experimental spectra are compared to spectra calculated by determining the eigenvalues of the Hamiltonian matrix describing helium Rydberg states in the external fields. The spectra and the calculated energy-level diagrams in external fields reveal avoided crossings between levels of different m ₗ values and pronounced m ₁-mixing effects at all angles between the electric- and magnetic-field vectors other than 0. These observations are discussed in the context of the development of a method to generate dense samples of cold atoms and molecules in a magnetic trap following Rydberg-Stark deceleration.

•Apr 1, 2016•5 citations

Time resolved fluorescence of Stark mixed He doubly excited states below He+(n = 2)

Francis Jean Penent, P. Lablanquie, M. Žitnik +2 more

The effect of a weak electric field on helium doubly excited states has been analyzed by time resolved fluorescence spectroscopy as a function of the E-field amplitude and relative orientation with respect to synchrotron light polarization. In addition to the possible excitation of parity forbidden states (i.e. 2pnp 1P e ), the effect of the weak Stark mixing induces a strong variation of fluorescence signal and decay lifetime for the states with an unfavored autoionization decay. For 2pnd 1 P o states a strong quenching of the fluorescence decay is observed when the E-field is parallel to the incident light polarization due to their mixing with 2sns 1 S e dark states.

Journal of Physics Conference Series•Nov 1, 2009•0 citations

Angular distribution of the fluorescence of helium doubly photo-excited states converging on the He+(N= 2) ionization threshold

J G Lambourne, Francis Jean Penent, P. Lablanquie +9 more

The asymmetry parameter β for fluorescence photons emitted during the radiative decay of the sp2, n +( 1 P o ), sp2, n −( 1 P o ), 2p n d( 1 P o ) and 2p n d( 3 D o ) series of helium doubly excited states, formed by the absorption of linearly polarized synchrotron radiation, has been measured. The results are compared with recent theoretical calculations (Žitnik et al 2002 Phys. Rev. A 65 032520). At high n the β parameter is shown to increase and oscillate due to the excitation of triplet states, optically accessible from the helium ground state due to spin–orbit effects.

Journal of Physics B Atomic Molecular and Optical Physics•Oct 20, 2003•14 citations
We present a theoretical framework for the calculation of photon-yield spectra from radiative-cascade decays of photoexcited helium atoms in a static electric field for incident photon energies below the first (N=1N=1N=1) ionization threshold. The present theory takes full account of the singlet-triplet mixing among the singly excited states with principal quantum numbers $n\ensuremath{\lesssim}10$. The model predicts the enhancement of transition probabilities to triplet final states due to the field-induced mixing. In particular, for a field strength of 9.17 kV/cm, polarization of incident photons perpendicular to the field, and a 4 meV broad excitation function tuned to the 1s6p1P1s6p\phantom{\rule{0.16em}{0ex}}{}^{1}\phantom{\rule{-0.16em}{0ex}}P1s6p1P states, the $1s6\ensuremath{\ell}\ensuremath{\rightarrow}1s2p\phantom{\rule{0.16em}{0ex}}{}^{3}\phantom{\rule{-0.16em}{0ex}}P$ and $1s5\ensuremath{\ell}\ensuremath{\rightarrow}1s2p\phantom{\rule{0.16em}{0ex}}{}^{3}\phantom{\rule{-0.16em}{0ex}}P$ emitted photon yields are predicted to be about 70 times and 20 times lower, respectively, than the photon yields for transitions to the corresponding singlet final states.
Doubly excited states below the N=2N=2N=2 ionization threshold are populated by exciting helium atoms in a supersonic beam with monochromatized synchrotron radiation. The fluorescence decay of these states triggers a radiative cascade back to the ground state with large probability to populate long lived singlet and triplet helium metastable states. The yield of metastables is measured using a multichannel plate detector after the beam has passed a singlet-quenching discharge lamp. The variation of the yield observed with the lamp switched on or off is related to the triplet-singlet mixing of the doubly excited states.
The fluorescence yield quenching of low-lying doubly excited 2pnd2pnd2pnd 1Po^{1}{P}^{o}1Po states is observed to depend strongly on a dc electric field strength and its orientation with respect to the polarization of the incoming photon beam. The reduction of the yield accompanied by the lifetime shortening is attributed to the Stark mixing with the neighboring 2sns2sns2sns 1Se^{1}{S}^{e}1Se states, which redirects the 2pnd2pnd2pnd 1Po^{1}{P}^{o}1Po decay to the prompt autoionization channel. For $n\ensuremath{\ge}4$, the lifetimes decrease from several hundred picoseconds down to several tens of picoseconds when an electric field in the kV/cm range is applied parallel to the photon probe polarization. Practically no lifetime change is observed for polarization perpendicular to the electric field direction. The results of the complex-scaling calculations are in a good agreement with the experimental data.
A spectroscopic study of Rydberg states of helium (n = 30 and 45) in magnetic, electric and combined magnetic and electric fields with arbitrary relative orientations of the field vectors is presented. The emphasis is on two special cases where (i) the diamagnetic term is negligible and both paramagnetic Zeeman and Stark effects are linear (n = 30, B ≤ 120 mT and F = 0-78 V cm⁻¹), and (ii) the diamagnetic term is dominant and the Stark effect is linear (n = 45, B = 277 mT and F = 0-8 V cm⁻¹). Both cases correspond to regimes where the interactions induced by the electric and magnetic fields are much weaker than the Coulomb interaction, but much stronger than the spin-orbit interaction. The experimental spectra are compared to spectra calculated by determining the eigenvalues of the Hamiltonian matrix describing helium Rydberg states in the external fields. The spectra and the calculated energy-level diagrams in external fields reveal avoided crossings between levels of different m ₗ values and pronounced m ₁-mixing effects at all angles between the electric- and magnetic-field vectors other than 0. These observations are discussed in the context of the development of a method to generate dense samples of cold atoms and molecules in a magnetic trap following Rydberg-Stark deceleration.
The effect of a weak electric field on helium doubly excited states has been analyzed by time resolved fluorescence spectroscopy as a function of the E-field amplitude and relative orientation with respect to synchrotron light polarization. In addition to the possible excitation of parity forbidden states (i.e. 2pnp 1P e ), the effect of the weak Stark mixing induces a strong variation of fluorescence signal and decay lifetime for the states with an unfavored autoionization decay. For 2pnd 1 P o states a strong quenching of the fluorescence decay is observed when the E-field is parallel to the incident light polarization due to their mixing with 2sns 1 S e dark states.
The asymmetry parameter β for fluorescence photons emitted during the radiative decay of the sp2, n +( 1 P o ), sp2, n −( 1 P o ), 2p n d( 1 P o ) and 2p n d( 3 D o ) series of helium doubly excited states, formed by the absorption of linearly polarized synchrotron radiation, has been measured. The results are compared with recent theoretical calculations (Žitnik et al 2002 Phys. Rev. A 65 032520). At high n the β parameter is shown to increase and oscillate due to the excitation of triplet states, optically accessible from the helium ground state due to spin–orbit effects.