Physical Review A

Dipole-dipole collision-induced transport of resonance excitation in a high-density atomic vapor

H. van Kampen, Vladimir A. Sautenkov, Anatolii M. Shalagin, E. R. Eliel, J. P. Woerdman

Published Nov 1, 1997• 40 citations

Abstract

We have experimentally studied the nonradiative transport of excitation in a dense $[N$=(0.3-2.5)\ifmmode\times\else\texttimes\fi{}${10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}]$ potassium vapor. We show that in such a high-density vapor the diffusive nonradiative transport of excitation via ``hopping'' of excitation in dipole-dipole collisions between excited- and ground-state atoms is dominant over the radiative transport through photons. The nonradiative transport mechanism becomes visible in the fluorescence-excitation spectrum signal as a sharp dip close to the resonance frequency. The appearance of the dip, its shape, width, and density dependence can all be explained in terms of a simple diffusion model for the nonradiative transport. This yields values for the diffusion coefficient and the resonance-exchange rate coefficient.

DOI: 10.1103/physreva.56.3569

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Nonradiative transport of atomic excitation in Na vapor

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Physical Review A

Dipole-dipole collision-induced transport of resonance excitation in a high-density atomic vapor

H. van Kampen, Vladimir A. Sautenkov, Anatolii M. Shalagin, E. R. Eliel, J. P. Woerdman

Published Nov 1, 1997• 40 citations

Publisher

Abstract

We have experimentally studied the nonradiative transport of excitation in a dense

[N

=(0.3-2.5)\ifmmode\times\else\texttimes\fi{}

{10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}]

potassium vapor. We show that in such a high-density vapor the diffusive nonradiative transport of excitation via ``hopping'' of excitation in dipole-dipole collisions between excited- and ground-state atoms is dominant over the radiative transport through photons. The nonradiative transport mechanism becomes visible in the fluorescence-excitation spectrum signal as a sharp dip close to the resonance frequency. The appearance of the dip, its shape, width, and density dependence can all be explained in terms of a simple diffusion model for the nonradiative transport. This yields values for the diffusion coefficient and the resonance-exchange rate coefficient.

DOI: 10.1103/physreva.56.3569

Related papers

Nonradiative transport of atomic excitation in Na vapor

Arthur Zajonc, A. V. Phelps

Measurements are reported which show the effect of nonradiative losses at a gas-window interface on the backscattered fluorescence intensity for Na vapor at frequencies in the vicinity of the resonance lines near 589 nm. The Na $3{P}_{\frac{1}{2},\frac{3}{2}}$ states are excited with a low-intensity single-mode tunable dye laser at high Na densities and the frequency integral of the backscattered fluorescence intensity in the $D1$ and $D2$ lines is measured. As the laser is tuned through resonance, the loss of atomic excitation to the window appears as a sharp decrease in the frequency-integrated fluorescence intensity. For example, at 7\ifmmode\times\else\texttimes\fi{} ${10}^{20}$ atoms ${\mathrm{m}}^{\ensuremath{-}3}$ the fluorescence intensity decreases by a factor of 4 in a frequency interval of 4 GHz. Measured absolute fluorescence intensities versus laser frequency are compared with predictions made using the theory of Hummer and Kunasz which includes both radiative and nonradiative transport processes. The agreement between theory and experiment is remarkably good when one considers that the theory contains only one unknown coefficient, i.e., the reflection coefficient for excited atoms at the windows. In our case the excited atoms are assumed to be completely destroyed at the window.Measurements are reported which show the effect of nonradiative losses at a gas-window interface on the backscattered fluorescence intensity for Na vapor at frequencies in the vicinity of the resonance lines near 589 nm. The Na $3{P}_{\frac{1}{2},\frac{3}{2}}$ states are excited with a low-intensity single-mode tunable dye laser at high Na densities and the frequency integral of the backscattered fluorescence intensity in the $D1$ and $D2$ lines is measured. As the laser is tuned through resonance, the loss of atomic excitation to the window appears as a sharp decrease in the frequency-integrated fluorescence intensity. For example, at 7\ifmmode\times\else\texttimes\fi{}${10}^{20}$ atoms ${\mathrm{m}}^{\ensuremath{-}3}$ the fluorescence intensity decreases by a factor of 4 in a frequency interval of 4 GHz. Measured absolute fluorescence intensities versus laser frequency are compared with predictions made using the theory of Hummer and Kunasz which includes both radiative and nonradiative transport processes. The agreement between theory and experiment is remarkably good when one considers that the theory contains only one unknown coefficient, i.e., the reflection coefficient for excited atoms at the windows. In our case the excited atoms are assumed to be completely destroyed at the window.

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Observation of collisional modification of the Zeeman effect in a high-density atomic vapor

H. van Kampen, A. Papoyan, Vladimir A. Sautenkov +3 more

We have studied the Zeeman effect of the resonance transition of atomic potassium vapor in a density range where the collision time is comparable with the time in between collisions. We find that the Zeeman splitting in this density range changes significantly as compared to the value for a free atom. In particular, we observe that the Zeeman effect of the two resonance $D$ lines become equal at the highest densities that we have studied. The modification of the Zeeman splitting is attributed to resonant dipole-dipole collisions between ground-state and excited-state atoms.We have studied the Zeeman effect of the resonance transition of atomic potassium vapor in a density range where the collision time is comparable with the time in between collisions. We find that the Zeeman splitting in this density range changes significantly as compared to the value for a free atom. In particular, we observe that the Zeeman effect of the two resonance $D$ lines become equal at the highest densities that we have studied. The modification of the Zeeman splitting is attributed to resonant dipole-dipole collisions between ground-state and excited-state atoms.

Physical Review AJul 1, 199715 citations

Transport of resonance excitation in Na vapor excited by white light

T. Fujimoto, A. V. Phelps

Experimental line profiles and integrated intensities for backscattered and forward-scattered resonance radiation using white-light excitation are compared with theory for Na densities between ${10}^{19}$ and ${10}^{22}$ atoms/ ${\mathrm{m}}^{3}$ . Absorption measurements are used to verify linewidth and line-wing asymmetry parameters and Na-vapor densities. The scattered spectral intensities are normalized to the incident flux using calibrated diffusers. Measurements of scattered intensities were also made as ${\mathrm{N}}_{2}$ was added to the Na. The line profiles and integrated intensities were calculated using a model which assumes complete redistribution of the radiation scattered by an atom and takes into account both radiative and nonradiative transport of the resonance excitation. The theory includes the effects of quenching by ${\mathrm{Na}}_{2}$ and by admixed ${\mathrm{N}}_{2}$ . With the white-light excitation used in these experiments the radiative transport is found to dominate the nonradiative transport except at wavelengths very near line center. The agreement between experimental and theoretical line profiles is good at high sodium densities (\ensuremath{\sim} 5 \ifmmode\times\else\texttimes\fi{} ${10}^{21}$ atoms/ ${\mathrm{m}}^{3}$ ) where instrumental resolution is not a serious limitation. The agreement between experimental and theoretical integrated intensities is within experimental error for Na densities of (1-10) \ifmmode\times\else\texttimes\fi{} ${10}^{19}$ and (2-5) \ifmmode\times\else\texttimes\fi{} ${10}^{21}$ atoms/ ${\mathrm{m}}^{3}$ . At the intermediate densities the approximately 20% discrepancy may be caused by the incomplete redistribution of radiation in the scattering process.Experimental line profiles and integrated intensities for backscattered and forward-scattered resonance radiation using white-light excitation are compared with theory for Na densities between ${10}^{19}$ and ${10}^{22}$ atoms/${\mathrm{m}}^{3}$. Absorption measurements are used to verify linewidth and line-wing asymmetry parameters and Na-vapor densities. The scattered spectral intensities are normalized to the incident flux using calibrated diffusers. Measurements of scattered intensities were also made as ${\mathrm{N}}_{2}$ was added to the Na. The line profiles and integrated intensities were calculated using a model which assumes complete redistribution of the radiation scattered by an atom and takes into account both radiative and nonradiative transport of the resonance excitation. The theory includes the effects of quenching by ${\mathrm{Na}}_{2}$ and by admixed ${\mathrm{N}}_{2}$. With the white-light excitation used in these experiments the radiative transport is found to dominate the nonradiative transport except at wavelengths very near line center. The agreement between experimental and theoretical line profiles is good at high sodium densities (\ensuremath{\sim} 5 \ifmmode\times\else\texttimes\fi{} ${10}^{21}$ atoms/${\mathrm{m}}^{3}$) where instrumental resolution is not a serious limitation. The agreement between experimental and theoretical integrated intensities is within experimental error for Na densities of (1-10) \ifmmode\times\else\texttimes\fi{} ${10}^{19}$ and (2-5) \ifmmode\times\else\texttimes\fi{} ${10}^{21}$ atoms/${\mathrm{m}}^{3}$. At the intermediate densities the approximately 20% discrepancy may be caused by the incomplete redistribution of radiation in the scattering process.

Physical Review AJan 1, 19826 citations

Dipole-Dipole Broadened Line Shape in a Partially Excited Dense Atomic Gas

Vladimir A. Sautenkov, H. van Kampen, E. R. Eliel +1 more

Physical Review LettersOct 14, 199681 citations

Effect of collisions on the resonance fluorescence spectrum

А. И. Пархоменко, Anatolii M. Shalagin

The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.

Journal of Experimental and Theoretical PhysicsMay 1, 20081 citation

Probing the spatial dispersion in a dense atomic vapor near a dielectric interface

H. van Kampen, Vladimir A. Sautenkov, E. R. Eliel +1 more

We have experimentally investigated the selective reflection of the $P\ensuremath{-}D$ transition in a high-density rubidium vapor and shown it to be sensitive to the exact spatial distribution of $P$ -state atoms near the dielectric-vapor interface. This distribution results from the radiative and nonradiative transport of excitation and from wall-quenching collisions of excited-state atoms and is highly inhomogeneous. Selective reflection thus acts as a probe of the spatial dispersion in the vapor. The resulting spectra have been analyzed to show that the broadening due to $S\ensuremath{-}D$ collisions contributes considerably to the self-broadened linewidth of the $P\ensuremath{-}D$ transition.We have experimentally investigated the selective reflection of the $P\ensuremath{-}D$ transition in a high-density rubidium vapor and shown it to be sensitive to the exact spatial distribution of $P$-state atoms near the dielectric-vapor interface. This distribution results from the radiative and nonradiative transport of excitation and from wall-quenching collisions of excited-state atoms and is highly inhomogeneous. Selective reflection thus acts as a probe of the spatial dispersion in the vapor. The resulting spectra have been analyzed to show that the broadening due to $S\ensuremath{-}D$ collisions contributes considerably to the self-broadened linewidth of the $P\ensuremath{-}D$ transition.

Physical Review ADec 1, 199812 citations

We have experimentally studied the nonradiative transport of excitation in a dense

[N

=(0.3-2.5)\ifmmode\times\else\texttimes\fi{}

{10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}]

3{P}_{\frac{1}{2},\frac{3}{2}}

states are excited with a low-intensity single-mode tunable dye laser at high Na densities and the frequency integral of the backscattered fluorescence intensity in the

D1

and

D2

lines is measured. As the laser is tuned through resonance, the loss of atomic excitation to the window appears as a sharp decrease in the frequency-integrated fluorescence intensity. For example, at 7\ifmmode\times\else\texttimes\fi{}

{10}^{20}

atoms ${\mathrm{m}}^{\ensuremath{-}3}$ the fluorescence intensity decreases by a factor of 4 in a frequency interval of 4 GHz. Measured absolute fluorescence intensities versus laser frequency are compared with predictions made using the theory of Hummer and Kunasz which includes both radiative and nonradiative transport processes. The agreement between theory and experiment is remarkably good when one considers that the theory contains only one unknown coefficient, i.e., the reflection coefficient for excited atoms at the windows. In our case the excited atoms are assumed to be completely destroyed at the window.

D

lines become equal at the highest densities that we have studied. The modification of the Zeeman splitting is attributed to resonant dipole-dipole collisions between ground-state and excited-state atoms.

Experimental line profiles and integrated intensities for backscattered and forward-scattered resonance radiation using white-light excitation are compared with theory for Na densities between

{10}^{19}

and

{10}^{22}

atoms/

{\mathrm{m}}^{3}

. Absorption measurements are used to verify linewidth and line-wing asymmetry parameters and Na-vapor densities. The scattered spectral intensities are normalized to the incident flux using calibrated diffusers. Measurements of scattered intensities were also made as

{\mathrm{N}}_{2}

was added to the Na. The line profiles and integrated intensities were calculated using a model which assumes complete redistribution of the radiation scattered by an atom and takes into account both radiative and nonradiative transport of the resonance excitation. The theory includes the effects of quenching by

{\mathrm{Na}}_{2}

and by admixed

{\mathrm{N}}_{2}

. With the white-light excitation used in these experiments the radiative transport is found to dominate the nonradiative transport except at wavelengths very near line center. The agreement between experimental and theoretical line profiles is good at high sodium densities (\ensuremath{\sim} 5 \ifmmode\times\else\texttimes\fi{}

{10}^{21}

atoms/

{\mathrm{m}}^{3}

) where instrumental resolution is not a serious limitation. The agreement between experimental and theoretical integrated intensities is within experimental error for Na densities of (1-10) \ifmmode\times\else\texttimes\fi{}

{10}^{19}

and (2-5) \ifmmode\times\else\texttimes\fi{}

{10}^{21}

atoms/

{\mathrm{m}}^{3}

. At the intermediate densities the approximately 20% discrepancy may be caused by the incomplete redistribution of radiation in the scattering process.

We have experimentally investigated the selective reflection of the $P\ensuremath{-}D$ transition in a high-density rubidium vapor and shown it to be sensitive to the exact spatial distribution of

P

-state atoms near the dielectric-vapor interface. This distribution results from the radiative and nonradiative transport of excitation and from wall-quenching collisions of excited-state atoms and is highly inhomogeneous. Selective reflection thus acts as a probe of the spatial dispersion in the vapor. The resulting spectra have been analyzed to show that the broadening due to $S\ensuremath{-}D$ collisions contributes considerably to the self-broadened linewidth of the $P\ensuremath{-}D$ transition.