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

Determination of the atom’s excited-state fraction in a magneto-optical trap

Yue Guo Shen

Published Jan 1, 2018• 0 citations
Publisher

Abstract

This thesis introduces an empirical method for determining and controlling the excited-state fraction of atoms in a magneto-optical trap (MOT), which is essential for the use of cold atoms as a sensor when they are held in a MOT since their interactions with other particles and fields are quantum state dependent. A four-level theoretical atomic model was used to describe the transitions of the atoms in a MOT, and the fluorescence emitted from a fixed number of atoms under different laser conditions were measured to determine the saturation parameters empirically. Two saturation parameters P_sat= 1.15 (0.06) mW and P_r,sat= 2.05 (0.59) mW were successfully extracted from the model, and the excited-state fraction in the four-level model was accurately calculated as a function of the MOT trap parameters, which ranges from 0.045 to 0.415 for the experimental settings currently available. We also observed minor deviations from the four-level model for the photon scattering rate, and a hypothesis of atom pinning under high powers was proposed to explain the problem. We plan to use this simple excited-state fraction determination method to distinguish the ground and excited state collision cross section of Rubidium atoms with species in residual gas of the vacuum. This is the first step to establishing atom loss rates from a MOT as an atomic primary pressure standard.

DOI
10.14288/1.0372961

Related papers

Photon-scattering-rate measurement of atoms in a magneto-optical trap

Kais Jooya, Nam Musterer, Kirk W. Madison +1 more

We present a technique for empirically determining the photon scattering rate of atoms in a magneto-optical trap (MOT). An accurate measurement of the scattering rate provides a way to accurately determine the number of atoms in the MOT, the excited-state fraction, and the in situ light intensity experienced by the atoms in the trap. We validate this technique for determining the scattering rate by comparing the atom number determined by the fluorescence emitted by atoms in a MOT with an independent and unrelated measure of the number determined by an absorption measurement of an optical pumping beam. We also observe minor deviations from the two-level model for the single-photon scattering rate and extend our analysis to a four-level model. The main advantage of the method described here is that it provides a simple way of determining the photon scattering rate of the MOT empirically and, thus, of evaluating the atom number from fluorescence measurements more accurately.

Physical Review A•Dec 2, 2013•9 citations

Model-independent measurements of the sodium magneto-optical trap's excited-state population

Jonathan M. Kwolek, D. S. Goodman, Samuel Entner +3 more

We present model-independent measurements of the excited-state population of atoms in a sodium (Na) magneto-optical trap (MOT) using a hybrid ion-neutral trap composed of a MOT and a linear Paul trap (LPT). We photoionize excited Na atoms trapped in the MOT and use two independent methods to measure the resulting ions: directly by trapping them in our LPT, and indirectly by monitoring changes in MOT fluorescence. By measuring the ionization rate via these two independent methods, we have enough information to directly determine the population of MOT atoms in the excited state. The resulting measurement reveals that there is a range of trapping-laser intensities where the excited-state population of atoms in our MOT follows the standard two-level model intensity dependence. However, an experimentally determined effective saturation intensity must be used instead of the theoretically predicted value from the two-level model. We measured the effective saturation intensity to be ${I}_{\mathrm{SE}}=22.9\ifmmode\pm\else\textpm\fi{}5.1\phantom{\rule{0.222222em}{0ex}}\mathrm{mW}/{\mathrm{cm}}^{2}$ for the type-I Na MOT and ${I}_{\mathrm{SE}}=49\ifmmode\pm\else\textpm\fi{}11\phantom{\rule{0.28em}{0ex}}\mathrm{mW}/{\mathrm{cm}}^{2}$ for the type-II Na MOT, approximately 1.7 and 3.6 times the theoretical estimate, respectively. Lastly, at large trapping-laser intensities, our experiment reveals a clear departure from the two-level model at a critical intensity that we believe is due to a state-mixing effect, the critical intensity of which can be determined by a simple power broadening model.

arXiv:1802.05306•Physical Review A•May 31, 2018•11 citations

Loss of cold atoms due to collisions with residual gases in free flight and in a magneto-optical trap

Jingfeng Xiang, He-Nan Cheng, Xiangkai Peng +14 more

The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was measured in a magneto-optical trap (MOT) and during its free flight. The residual gas pressure was analyzed by a residual gas analyzer, and the pressure distribution in a vacuum chamber was numerically calculated by the angular coefficient method. The decay factor, which describes the decay behavior of cold atoms due to residual gas collisions during a free flight, was calculated. It was found that the decay factor agrees well with theoretical predictions under various vacuum conditions.

Chinese Physics B•Jul 1, 2018•10 citations

Electron collision studies of cesium using a magneto-optical trap.

J. A. MacAskill

Experiments involving a magneto-optical trap (MOT) as the target in electron impact cross section studies were carried out. The use of a MOT allows the kinematic properties of the target atoms, and their electronic states, to be controlled via operating parameters of the MOT's lasers. A MOT is capable of saturating the excited state of a gaseous target of atoms and provides a unique opportunity to measure exotic collision processes. Measurements use a trap-loss technique to relate the loss rate of atoms from the trap due to electron interactions to a collision cross section. Total scattering cross section measurements are given for the 62S 1/2 ground state and the 62P3/2 excited state of cesium. The excited state measurement is the first measurement of its kind. Total ionization cross sections are also presented for the both the 6 2S1/2 ground state and 62P3/2 excited state. The ionization cross sections are measured by adjusting the radiation force of the MOT lasers to damp the elastic scattering component of the total cross section. The ionization cross section for the excited state is the first experimental determination of its kind. Full details of the experimental apparatus and the analysis procedure are presented. The results of this experiment are combined with other experimental data and compared to the most recent calculations.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .M322. Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4996. Adviser: J. W. McConkey. Thesis (Ph.D.)--University of Windsor (Canada), 2003.

•Oct 1, 2003•1 citation

A Study of Excited State Atoms in Cold Atom Traps and a test of the Reif Model to Determine Trap Depth.

N. Evetts

The motivation, theory and applications of atomic traps are briefly reviewed before delving into the primary motivation for the research: the disagreement between theory and experiment for the calculation of trap loss rate constants (< σv >) for Rubidium Magneto-Optical Traps. We use a pure magnetic trap to calibrate for the density of background Rubidium in our system while varying this density and measuring the loss and loading rates for multiple magnetic traps for which the trap depth has been measured previously. This variation of density allows us to infer < σv >, a quantity whose behaviour we attempt to explain in relation to the the excited state fraction of the trapped atoms. We find a strong correlation between the excited state fraction and the loss rate constant which we are, unfortunately, unable to quantify due to data quality issues. In addition to this study, experimental evidence for the confirmation of the Reif Model is provided as well as a new method (based on this model) for measuring the depth of a magneto-optical trap.

•Jan 1, 2011•1 citation

Model-free measurement of the excited-state fraction in a Rb85 magneto-optical trap

G. Veshapidze, J. Bang, C. W. Fehrenbach +2 more

In many experiments involving magneto-optical traps (MOTs), it is imperative to know the fraction of atoms left in an excited state by the cooling and trapping lasers. In most cases, researchers have used formulas that were derived for simple two-level systems interacting with a single beam of light having a well-defined polarization, and in the absence of magnetic or electric fields. However, a MOT environment is much more complex than this. Here we directly measure the excited fraction in a MOT of $^{85}\mathrm{Rb}$ atoms in a model-independent manner for a wide range of trapping conditions. We then fit our measured fractions to an ansatz based on a simple model. Knowing only the trapping laser's total intensity and detuning from resonance, one can then use this ansatz to accurately predict the excited fraction. The work is a companion piece to similar measurements on a MOT of $^{87}\mathrm{Rb}$.

Physical Review A•May 27, 2015•10 citations
This thesis introduces an empirical method for determining and controlling the excited-state fraction of atoms in a magneto-optical trap (MOT), which is essential for the use of cold atoms as a sensor when they are held in a MOT since their interactions with other particles and fields are quantum state dependent. A four-level theoretical atomic model was used to describe the transitions of the atoms in a MOT, and the fluorescence emitted from a fixed number of atoms under different laser conditions were measured to determine the saturation parameters empirically. Two saturation parameters P_sat= 1.15 (0.06) mW and P_r,sat= 2.05 (0.59) mW were successfully extracted from the model, and the excited-state fraction in the four-level model was accurately calculated as a function of the MOT trap parameters, which ranges from 0.045 to 0.415 for the experimental settings currently available. We also observed minor deviations from the four-level model for the photon scattering rate, and a hypothesis of atom pinning under high powers was proposed to explain the problem. We plan to use this simple excited-state fraction determination method to distinguish the ground and excited state collision cross section of Rubidium atoms with species in residual gas of the vacuum. This is the first step to establishing atom loss rates from a MOT as an atomic primary pressure standard.
We present a technique for empirically determining the photon scattering rate of atoms in a magneto-optical trap (MOT). An accurate measurement of the scattering rate provides a way to accurately determine the number of atoms in the MOT, the excited-state fraction, and the in situ light intensity experienced by the atoms in the trap. We validate this technique for determining the scattering rate by comparing the atom number determined by the fluorescence emitted by atoms in a MOT with an independent and unrelated measure of the number determined by an absorption measurement of an optical pumping beam. We also observe minor deviations from the two-level model for the single-photon scattering rate and extend our analysis to a four-level model. The main advantage of the method described here is that it provides a simple way of determining the photon scattering rate of the MOT empirically and, thus, of evaluating the atom number from fluorescence measurements more accurately.
We present model-independent measurements of the excited-state population of atoms in a sodium (Na) magneto-optical trap (MOT) using a hybrid ion-neutral trap composed of a MOT and a linear Paul trap (LPT). We photoionize excited Na atoms trapped in the MOT and use two independent methods to measure the resulting ions: directly by trapping them in our LPT, and indirectly by monitoring changes in MOT fluorescence. By measuring the ionization rate via these two independent methods, we have enough information to directly determine the population of MOT atoms in the excited state. The resulting measurement reveals that there is a range of trapping-laser intensities where the excited-state population of atoms in our MOT follows the standard two-level model intensity dependence. However, an experimentally determined effective saturation intensity must be used instead of the theoretically predicted value from the two-level model. We measured the effective saturation intensity to be ${I}_{\mathrm{SE}}=22.9\ifmmode\pm\else\textpm\fi{}5.1\phantom{\rule{0.222222em}{0ex}}\mathrm{mW}/{\mathrm{cm}}^{2}$ for the type-I Na MOT and ${I}_{\mathrm{SE}}=49\ifmmode\pm\else\textpm\fi{}11\phantom{\rule{0.28em}{0ex}}\mathrm{mW}/{\mathrm{cm}}^{2}$ for the type-II Na MOT, approximately 1.7 and 3.6 times the theoretical estimate, respectively. Lastly, at large trapping-laser intensities, our experiment reveals a clear departure from the two-level model at a critical intensity that we believe is due to a state-mixing effect, the critical intensity of which can be determined by a simple power broadening model.
The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was measured in a magneto-optical trap (MOT) and during its free flight. The residual gas pressure was analyzed by a residual gas analyzer, and the pressure distribution in a vacuum chamber was numerically calculated by the angular coefficient method. The decay factor, which describes the decay behavior of cold atoms due to residual gas collisions during a free flight, was calculated. It was found that the decay factor agrees well with theoretical predictions under various vacuum conditions.
Experiments involving a magneto-optical trap (MOT) as the target in electron impact cross section studies were carried out. The use of a MOT allows the kinematic properties of the target atoms, and their electronic states, to be controlled via operating parameters of the MOT's lasers. A MOT is capable of saturating the excited state of a gaseous target of atoms and provides a unique opportunity to measure exotic collision processes. Measurements use a trap-loss technique to relate the loss rate of atoms from the trap due to electron interactions to a collision cross section. Total scattering cross section measurements are given for the 62S 1/2 ground state and the 62P3/2 excited state of cesium. The excited state measurement is the first measurement of its kind. Total ionization cross sections are also presented for the both the 6 2S1/2 ground state and 62P3/2 excited state. The ionization cross sections are measured by adjusting the radiation force of the MOT lasers to damp the elastic scattering component of the total cross section. The ionization cross section for the excited state is the first experimental determination of its kind. Full details of the experimental apparatus and the analysis procedure are presented. The results of this experiment are combined with other experimental data and compared to the most recent calculations.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .M322. Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4996. Adviser: J. W. McConkey. Thesis (Ph.D.)--University of Windsor (Canada), 2003.
The motivation, theory and applications of atomic traps are briefly reviewed before delving into the primary motivation for the research: the disagreement between theory and experiment for the calculation of trap loss rate constants (< σv >) for Rubidium Magneto-Optical Traps. We use a pure magnetic trap to calibrate for the density of background Rubidium in our system while varying this density and measuring the loss and loading rates for multiple magnetic traps for which the trap depth has been measured previously. This variation of density allows us to infer < σv >, a quantity whose behaviour we attempt to explain in relation to the the excited state fraction of the trapped atoms. We find a strong correlation between the excited state fraction and the loss rate constant which we are, unfortunately, unable to quantify due to data quality issues. In addition to this study, experimental evidence for the confirmation of the Reif Model is provided as well as a new method (based on this model) for measuring the depth of a magneto-optical trap.
In many experiments involving magneto-optical traps (MOTs), it is imperative to know the fraction of atoms left in an excited state by the cooling and trapping lasers. In most cases, researchers have used formulas that were derived for simple two-level systems interacting with a single beam of light having a well-defined polarization, and in the absence of magnetic or electric fields. However, a MOT environment is much more complex than this. Here we directly measure the excited fraction in a MOT of 85Rb^{85}\mathrm{Rb}85Rb atoms in a model-independent manner for a wide range of trapping conditions. We then fit our measured fractions to an ansatz based on a simple model. Knowing only the trapping laser's total intensity and detuning from resonance, one can then use this ansatz to accurately predict the excited fraction. The work is a companion piece to similar measurements on a MOT of 87Rb^{87}\mathrm{Rb}87Rb.