Physical Review A

Coupled-channel analysis of Ne* thermalization cross section

V. P. Mogendorff, Edgar J. D. Vredenbregt, Herman C. W. Beijerinck

Published Jan 18, 2006• 1 citation

Abstract

We investigate the relation between the thermalization cross section ${⟨\ensuremath{\sigma}⟩}_{T}$ and the scattering length $a$ of spin-polarized metastable neon $({\mathrm{Ne}}^{*})$ in the Doppler-limited temperature regime. We show that a temperature-dependent, quantum-mechanical, five-channel calculation allows one to obtain $a$ consistent with the mass scaling rule between $^{20}\mathrm{Ne}^{*}$ and $^{22}\mathrm{Ne}^{*}$ from recent data of ${⟨\ensuremath{\sigma}⟩}_{T}$ by Spoden et al. [Phys. Rev. Lett. 94, 223201 (2005)]. We find $a=+{24}_{\ensuremath{-}5}^{+5}{a}_{0}$ or $a=\ensuremath{-}{128}_{\ensuremath{-}22}^{+16}{a}_{0}$ for $^{20}\mathrm{Ne}^{*}$ and $+115\ensuremath{\lesssim}a\ensuremath{\lesssim}+160{a}_{0}$ for $^{22}\mathrm{Ne}^{*}$, respectively. According to numerical simulations of the evaporative cooling process, these values of $a$ are not large enough to make Bose-Einstein condensation of ${\mathrm{Ne}}^{*}$ feasible for realistic experimental conditions, given the measured ionization rate constants.

DOI: 10.1103/physreva.73.012712

Related papers

Metastable neon collisions: Anisotropy and scattering length

V. P. Mogendorff, Edgar J. D. Vredenbregt, BOUDEWIJN J. VERHAAR +1 more

arXiv:physics/0309053Physical Review AJan 15, 20044 citations

Cold collisions of metastable neon atoms

Christian Cop

Jan 1, 20170 citations

Rethermalizing collisions between magnetically trapped metastable neon atoms

V. P. Mogendorff, BJ Bert Claessens, S. J. M. Kuppens +2 more

May 1, 20020 citations

Prospects for Bose-Einstein condensation of metastable neon atoms

Herman C. W. Beijerinck, Edgar J. D. Vredenbregt, R. J. W. Stas +2 more

Physical Review AJan 18, 200010 citations

Heteronuclear collisions between laser-cooled metastable neon atoms

Jan Schütz, Thomas Feldker, Holger John +1 more

arXiv:1208.5719Physical Review AAug 24, 20124 citations

Interaction of cold metastable neon atoms - towards Bose-Einstein condensation of neon

P. Spodem, Tobias Kraemer, A. Bunkowski +3 more

European Quantum Electronics Conference (EQEC)Oct 19, 20040 citations

Physical Review A

Coupled-channel analysis of Ne* thermalization cross section

V. P. Mogendorff, Edgar J. D. Vredenbregt, Herman C. W. Beijerinck

Published Jan 18, 2006• 1 citation

Publisher

Abstract

We investigate the relation between the thermalization cross section

{⟨\ensuremath{\sigma}⟩}_{T}

and the scattering length

a

of spin-polarized metastable neon

({\mathrm{Ne}}^{*})

in the Doppler-limited temperature regime. We show that a temperature-dependent, quantum-mechanical, five-channel calculation allows one to obtain

a

consistent with the mass scaling rule between

^{20}\mathrm{Ne}^{*}

and

^{22}\mathrm{Ne}^{*}

from recent data of

{⟨\ensuremath{\sigma}⟩}_{T}

by Spoden et al. [Phys. Rev. Lett. 94, 223201 (2005)]. We find

a=+{24}_{\ensuremath{-}5}^{+5}{a}_{0}

a=\ensuremath{-}{128}_{\ensuremath{-}22}^{+16}{a}_{0}

for

^{20}\mathrm{Ne}^{*}

and

+115\ensuremath{\lesssim}a\ensuremath{\lesssim}+160{a}_{0}

for

^{22}\mathrm{Ne}^{*}

, respectively. According to numerical simulations of the evaporative cooling process, these values of

a

are not large enough to make Bose-Einstein condensation of

{\mathrm{Ne}}^{*}

feasible for realistic experimental conditions, given the measured ionization rate constants.

DOI: 10.1103/physreva.73.012712

Related papers

Metastable neon collisions: Anisotropy and scattering length

V. P. Mogendorff, Edgar J. D. Vredenbregt, BOUDEWIJN J. VERHAAR +1 more

In this paper we investigate the effective scattering length a of spin-polarized ${\mathrm{Ne}}^{*}.$ Due to its anisotropic electrostatic interaction, its scattering length is determined by five interaction potentials instead of one, even in the spin-polarized case, a unique property among the Bose condensed species and candidates. Because the interaction potentials of ${\mathrm{Ne}}^{*}$ are not known accurately enough to predict the value of the scattering length, we investigate the behavior of a as a function of the five phase integrals ${\ensuremath{\Phi}}_{\ensuremath{\Omega}}$ corresponding to the five interaction potentials. We find that the scattering length has five resonances instead of only one and cannot be described by a simple gas-kinetic approach or the degenerate internal state (DIS) approximation. However, the probability for finding a positive or large value of the scattering length is not enhanced compared to the single-potential case. We find that the induced dipole-dipole interaction enables strong coupling between the different $|J\ensuremath{\Omega}{\mathrm{PM}}_{P}〉$ states, resulting in an inhomogeneous shift of the resonance positions and widths in the quantum-mechanical calculation as compared to the DIS approach. The dependence of the resonance positions and widths on the input potentials turns out to be rather straightforward. The existence of two bosonic isotopes of ${\mathrm{Ne}}^{*}$ enables us to choose the isotope with the most favorable scattering length for efficient evaporative cooling towards the Bose-Einstein condensation transition, greatly enhancing the feasibility to reach this transition.In this paper we investigate the effective scattering length a of spin-polarized ${\mathrm{Ne}}^{*}.$ Due to its anisotropic electrostatic interaction, its scattering length is determined by five interaction potentials instead of one, even in the spin-polarized case, a unique property among the Bose condensed species and candidates. Because the interaction potentials of ${\mathrm{Ne}}^{*}$ are not known accurately enough to predict the value of the scattering length, we investigate the behavior of a as a function of the five phase integrals ${\ensuremath{\Phi}}_{\ensuremath{\Omega}}$ corresponding to the five interaction potentials. We find that the scattering length has five resonances instead of only one and cannot be described by a simple gas-kinetic approach or the degenerate internal state (DIS) approximation. However, the probability for finding a positive or large value of the scattering length is not enhanced compared to the single-potential case. We find that the induced dipole-dipole interaction enables strong coupling between the different $|J\ensuremath{\Omega}{\mathrm{PM}}_{P}〉$ states, resulting in an inhomogeneous shift of the resonance positions and widths in the quantum-mechanical calculation as compared to the DIS approach. The dependence of the resonance positions and widths on the input potentials turns out to be rather straightforward. The existence of two bosonic isotopes of ${\mathrm{Ne}}^{*}$ enables us to choose the isotope with the most favorable scattering length for efficient evaporative cooling towards the Bose-Einstein condensation transition, greatly enhancing the feasibility to reach this transition.

arXiv:physics/0309053Physical Review AJan 15, 20044 citations

Cold collisions of metastable neon atoms

Christian Cop

In this thesis we investigate theoretically the cold collision properties of metastable neon (Ne*). The collisions of metastable rare gases (Rg*) exhibit a plethora of interesting phenomena: Due to the high internal excitation energies of the metastable atoms ionization processes are very likely. The produced ions can be detected with single-ion efficiency in the experiment. In experiments with atomic Rg* gases at cold temperatures T~1 mK, this allows for in-situ monitoring of the real-time dynamics of the atomic gas and for example for the study of two-particle correlations. Furthermore, in cold Rg* gases one can examine the prospects of creating a Bose-Einstein condensate or a degenerate Fermi gas of Rg*. Ne* is a promising candidate for Bose-Einstein condensation and in the group of G. Birkl the properties of cold gases of Ne* are investigated experimentally. Two-body loss rate coefficients due to the ionization processes and elastic cross sections have been measured. It is useful to complement the experimental measurements with a theoretical study in order to obtain a better understanding of the cold Ne* gases and the collision physics of Ne*. At the low temperatures of the atomic gases, these gases are dilute with particle number densities of n~10^9 cm^{-3}. For these low densities, the behavior of the gas is determined mainly by two-body collision physics which is solved by quantum scattering theory in terms of the S matrix. The collision physics is given by short-range interactions and long-range interactions of the atoms. The short-range and long-range interaction potentials of Ne* have been calculated in the molecular basis of Ne2. In this thesis we first calculate short-range and long-range interactions of atoms and molecular basis states of diatomic molecules with a simpler electronic structure than Ne* and Ne2 in order to introduce the notation and to discuss the characteristics of the calculated molecular interaction potentials and in order to employ them in the scattering calculations for Ne*. Instead of solving the full scattering equations by taking into account all the molecular interaction potentials, we demonstrate that the collision physics of Ne* can be described in terms of a coupled two-channel model with a single interaction potential only which describes the elastic scattering of Ne*. In this model, ionization in Ne* collisions is described by the transition of the upper elastic interaction channel to the lower channel, representing the loss or ionization channel. We introduce two versions of the two-channel model in this work. In the first version, the two channels are given by square-well potentials. We can solve the scattering equations analytically and for complex wave numbers k and study the solutions in the complex k plane. With an expansion of the S matrix in terms of its poles in the complex k plane we find a parametrization of the two-body loss rate coefficients. We show that these coefficients describe ionizing collisions of Ne* by comparing them to the experimental measurements and to the numerical results obtained by the two-channel model in the second version. In this second version of the two-channel model, the elastic scattering channel is given by a realistic interaction potential of Ne*, consisting of a calculated short-range and long-range molecular potential, and the loss channel by a model ionization potential. For this model we calculate the two-body loss rate coefficients and the elastic cross sections for the isotope mixtures of Ne* which have been measured experimentally and demonstrate that the free potential parameters can be optimized to the experimental data to achieve very good agreement of the numerical results with the experimental measurements. We discuss the validity of the two-channel model by comparing the results to existing models for cold Rg* collisions and find that the two-channel model of this work is a useful extension to these models.In this thesis we investigate theoretically the cold collision properties of metastable neon (Ne*). The collisions of metastable rare gases (Rg*) exhibit a plethora of interesting phenomena: Due to the high internal excitation energies of the metastable atoms ionization processes are very likely. The produced ions can be detected with single-ion efficiency in the experiment. In experiments with atomic Rg* gases at cold temperatures T~1 mK, this allows for in-situ monitoring of the real-time dynamics of the atomic gas and for example for the study of two-particle correlations. Furthermore, in cold Rg* gases one can examine the prospects of creating a Bose-Einstein condensate or a degenerate Fermi gas of Rg*. Ne* is a promising candidate for Bose-Einstein condensation and in the group of G. Birkl the properties of cold gases of Ne* are investigated experimentally. Two-body loss rate coefficients due to the ionization processes and elastic cross sections have been measured. It is useful to complement the experimental measurements with a theoretical study in order to obtain a better understanding of the cold Ne* gases and the collision physics of Ne*. At the low temperatures of the atomic gases, these gases are dilute with particle number densities of n~10^9 cm^{-3}. For these low densities, the behavior of the gas is determined mainly by two-body collision physics which is solved by quantum scattering theory in terms of the S matrix. The collision physics is given by short-range interactions and long-range interactions of the atoms. The short-range and long-range interaction potentials of Ne* have been calculated in the molecular basis of Ne2. In this thesis we first calculate short-range and long-range interactions of atoms and molecular basis states of diatomic molecules with a simpler electronic structure than Ne* and Ne2 in order to introduce the notation and to discuss the characteristics of the calculated molecular interaction potentials and in order to employ them in the scattering calculations for Ne*. Instead of solving the full scattering equations by taking into account all the molecular interaction potentials, we demonstrate that the collision physics of Ne* can be described in terms of a coupled two-channel model with a single interaction potential only which describes the elastic scattering of Ne*. In this model, ionization in Ne* collisions is described by the transition of the upper elastic interaction channel to the lower channel, representing the loss or ionization channel. We introduce two versions of the two-channel model in this work. In the first version, the two channels are given by square-well potentials. We can solve the scattering equations analytically and for complex wave numbers k and study the solutions in the complex k plane. With an expansion of the S matrix in terms of its poles in the complex k plane we find a parametrization of the two-body loss rate coefficients. We show that these coefficients describe ionizing collisions of Ne* by comparing them to the experimental measurements and to the numerical results obtained by the two-channel model in the second version. In this second version of the two-channel model, the elastic scattering channel is given by a realistic interaction potential of Ne*, consisting of a calculated short-range and long-range molecular potential, and the loss channel by a model ionization potential. For this model we calculate the two-body loss rate coefficients and the elastic cross sections for the isotope mixtures of Ne* which have been measured experimentally and demonstrate that the free potential parameters can be optimized to the experimental data to achieve very good agreement of the numerical results with the experimental measurements. We discuss the validity of the two-channel model by comparing the results to existing models for cold Rg* collisions and find that the two-channel model of this work is a useful extension to these models.

Jan 1, 20170 citations

Rethermalizing collisions between magnetically trapped metastable neon atoms

V. P. Mogendorff, BJ Bert Claessens, S. J. M. Kuppens +2 more

The successful Bose-Einstein Condensation (BEC) of alkali atoms has\nstimulated several groups to extend the range to metastable rare gas\natoms. In 2001 this resulted in the achievement of BEC with metastable\nhelium atoms (He^*) [1,2]. The only other rare gas atom suitable for\nachieving BEC is neon. The goal of our group is BEC of metastable neon\n(Ne^*). A condensate of metastable rare gas atoms is of special interest\nbecause their large internal energy enables real time diagnostics of the\nsample during condensation, giving new insight into the dynamics of the\nphase transition. Crucial for achieving BEC is a large (positive)\nscattering length. For He^* a good estimate of the order of magnitude of\nthe scattering length was known. For neon no such theoretical estimate\nexists, therefore, experimental data on the value of the scattering\nlength is necessary to determine whether or not BEC is feasible for\nNe^*. In recent thermalization experiments involving two RF-knives,\nsimilar to the scheme used by Aspect et al. [3], we have observed\nrethermalizing collisions in our magnetic trap. Moreover, preliminary\nmeasurements point in the direction of a large absolute value of the\nscattering length. In this presentation we will discuss these\nthermalization experiments, and hope to present a value of the\nscattering length. [1] A. Robert et al., Science 292, 461 (2001). [2]\nF.P. Dos-Santos et al., Phys. Rev. Lett. 86, 3459 (2001). [3] A.\nBrowaeys et al., Phys. Rev. A. 64, 034703 (2001).The successful Bose-Einstein Condensation (BEC) of alkali atoms has\nstimulated several groups to extend the range to metastable rare gas\natoms. In 2001 this resulted in the achievement of BEC with metastable\nhelium atoms (He^*) [1,2]. The only other rare gas atom suitable for\nachieving BEC is neon. The goal of our group is BEC of metastable neon\n(Ne^*). A condensate of metastable rare gas atoms is of special interest\nbecause their large internal energy enables real time diagnostics of the\nsample during condensation, giving new insight into the dynamics of the\nphase transition. Crucial for achieving BEC is a large (positive)\nscattering length. For He^* a good estimate of the order of magnitude of\nthe scattering length was known. For neon no such theoretical estimate\nexists, therefore, experimental data on the value of the scattering\nlength is necessary to determine whether or not BEC is feasible for\nNe^*. In recent thermalization experiments involving two RF-knives,\nsimilar to the scheme used by Aspect et al. [3], we have observed\nrethermalizing collisions in our magnetic trap. Moreover, preliminary\nmeasurements point in the direction of a large absolute value of the\nscattering length. In this presentation we will discuss these\nthermalization experiments, and hope to present a value of the\nscattering length. [1] A. Robert et al., Science 292, 461 (2001). [2]\nF.P. Dos-Santos et al., Phys. Rev. Lett. 86, 3459 (2001). [3] A.\nBrowaeys et al., Phys. Rev. A. 64, 034703 (2001).

May 1, 20020 citations

Prospects for Bose-Einstein condensation of metastable neon atoms

Herman C. W. Beijerinck, Edgar J. D. Vredenbregt, R. J. W. Stas +2 more

The calculated upper limit ${\mathcal{K}}_{i}^{\mathrm{pol}}<~{10}^{\ensuremath{-}14}{\mathrm{cm}}^{3}/\mathrm{s}$ of the rate constant for suppressed ionization in a gas of metastable $\mathrm{Ne}{(}^{3}{\mathrm{P}}_{2})$ atoms in the fully aligned $|{J=2,m}_{J}=2〉$ state is used as input to investigate the prospects for achieving Bose-Einstein condensation (BEC). The heating rate of the trap population by secondary collisions of the hot products of the process of ionization---i.e., ground-state atoms, ions, and dimer-ions---with cold trapped metastable atoms is discussed in terms of a semiclassical model. An important step lies in limiting the depth of the magnetic trap to a value of a few millikelvin, to limit the range of small-angle scattering that contributes to heating. Also, a tight radial confinement reduces the probability for secondary collisions. At a trap depth of 10 mK, a radial dimension of $3\ensuremath{\mu}\mathrm{m},$ and a density of $2\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{cm}}^{\ensuremath{-}3}$ the heating rate is $1.4\ensuremath{\mu}\mathrm{K}/\mathrm{s},$ which should be compared to the transition temperature to BEC of $0.6\ensuremath{\mu}\mathrm{K}.$ The collisional heating is dominated by ion---metastable-atom collisions, due to their long-range charge-induced dipole interaction. Keeping the evaporative cooling switched on at ${T=T}_{C}$ reduces the heating a hundredfold. Using a bright beam of laser cooled neon atoms, an initial population of $>~{10}^{10}$ atoms can be loaded into a magneto-optical trap in one second. Tight magnetic traps are easy to achieve for metastable neon atoms, due to their magnetic moment of $3{\ensuremath{\mu}}_{B}.$ We conclude that achieving BEC is feasible for metastable neon. This also holds for triplet metastable helium, once the loading rate of traps has been improved. Finally, the semiclassical model used for calculating the heating rate is applicable to a wide range of inelastic collisions in trapped alkali gases and/or collisions with background gas.The calculated upper limit ${\mathcal{K}}_{i}^{\mathrm{pol}}<~{10}^{\ensuremath{-}14}{\mathrm{cm}}^{3}/\mathrm{s}$ of the rate constant for suppressed ionization in a gas of metastable $\mathrm{Ne}{(}^{3}{\mathrm{P}}_{2})$ atoms in the fully aligned $|{J=2,m}_{J}=2〉$ state is used as input to investigate the prospects for achieving Bose-Einstein condensation (BEC). The heating rate of the trap population by secondary collisions of the hot products of the process of ionization---i.e., ground-state atoms, ions, and dimer-ions---with cold trapped metastable atoms is discussed in terms of a semiclassical model. An important step lies in limiting the depth of the magnetic trap to a value of a few millikelvin, to limit the range of small-angle scattering that contributes to heating. Also, a tight radial confinement reduces the probability for secondary collisions. At a trap depth of 10 mK, a radial dimension of $3\ensuremath{\mu}\mathrm{m},$ and a density of $2\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{cm}}^{\ensuremath{-}3}$ the heating rate is $1.4\ensuremath{\mu}\mathrm{K}/\mathrm{s},$ which should be compared to the transition temperature to BEC of $0.6\ensuremath{\mu}\mathrm{K}.$ The collisional heating is dominated by ion---metastable-atom collisions, due to their long-range charge-induced dipole interaction. Keeping the evaporative cooling switched on at ${T=T}_{C}$ reduces the heating a hundredfold. Using a bright beam of laser cooled neon atoms, an initial population of $>~{10}^{10}$ atoms can be loaded into a magneto-optical trap in one second. Tight magnetic traps are easy to achieve for metastable neon atoms, due to their magnetic moment of $3{\ensuremath{\mu}}_{B}.$ We conclude that achieving BEC is feasible for metastable neon. This also holds for triplet metastable helium, once the loading rate of traps has been improved. Finally, the semiclassical model used for calculating the heating rate is applicable to a wide range of inelastic collisions in trapped alkali gases and/or collisions with background gas.

Physical Review AJan 18, 200010 citations

Heteronuclear collisions between laser-cooled metastable neon atoms

Jan Schütz, Thomas Feldker, Holger John +1 more

We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable ( ${}^{3}\phantom{\rule{-0.16em}{0ex}}{P}_{2}$ ) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes ${}^{20}$ Ne, ${}^{21}$ Ne, and ${}^{22}$ Ne. We determine the rate coefficients for heteronuclear ionizing collisions to ${\ensuremath{\beta}}_{21,20}=(3.9\ifmmode\pm\else\textpm\fi{}2.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm ${}^{3}$ /s, ${\ensuremath{\beta}}_{22,20}=(2.6\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm ${}^{3}$ /s, and ${\ensuremath{\beta}}_{21,22}=(3.9\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm ${}^{3}$ /s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state.We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable (${}^{3}\phantom{\rule{-0.16em}{0ex}}{P}_{2}$) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes ${}^{20}$Ne, ${}^{21}$Ne, and ${}^{22}$Ne. We determine the rate coefficients for heteronuclear ionizing collisions to ${\ensuremath{\beta}}_{21,20}=(3.9\ifmmode\pm\else\textpm\fi{}2.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm${}^{3}$/s, ${\ensuremath{\beta}}_{22,20}=(2.6\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm${}^{3}$/s, and ${\ensuremath{\beta}}_{21,22}=(3.9\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm${}^{3}$/s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state.

arXiv:1208.5719Physical Review AAug 24, 20124 citations

Interaction of cold metastable neon atoms - towards Bose-Einstein condensation of neon

P. Spodem, Tobias Kraemer, A. Bunkowski +3 more

Summary form only given. The understanding of the interaction of ultracold atoms will be substantially extended by the experimental study of ultracold non-alkaline systems. Due to the special internal structure and the high internal energy, metastable noble gases will play a crucial role. The objective of our work is to attain a detailed study of the atomic structure and the interactions in a gas of ultracold metastable neon atoms. Ensembles of high phase space density and, if possible, Bose condensates shall be achieved. The elementary pair interaction as well as the collective interactions are to be characterized. Of special interest is Penning ionization as it is the main loss process in dense metastable atom traps. The degree of its suppression in a spin polarized gas will strongly affect the feasibility of a quantum-degenerate system of metastable atoms. In addition, metastable noble gas atoms will allow the implementation of novel diagnostics for the investigation of Bose condensates due to their high detectability. We want to make use of this advantage in order to investigate higher order correlation functions and study the laser-like behavior of Bose condensates and atom-laser outputs. We have achieved loading of 4/spl times/10/sup 8/ atoms in a magneto-optical trap (MOT) and after efficient spin polarization of 2.5 /spl times/ 10/sup 8/ atoms in a Ioffe-Pritchard-type magnetic trap. We present a precision measurement of the lifetime of the 3s[3/2]/sub 2/-metastable state of neon which we could determine to 14.70(13)s. We report on the status of the determination of the elastic scattering rate, the rates of Penning ionization for spin-polarized and non-spin-polarized atom samples, and the implementation of evaporative cooling.Summary form only given. The understanding of the interaction of ultracold atoms will be substantially extended by the experimental study of ultracold non-alkaline systems. Due to the special internal structure and the high internal energy, metastable noble gases will play a crucial role. The objective of our work is to attain a detailed study of the atomic structure and the interactions in a gas of ultracold metastable neon atoms. Ensembles of high phase space density and, if possible, Bose condensates shall be achieved. The elementary pair interaction as well as the collective interactions are to be characterized. Of special interest is Penning ionization as it is the main loss process in dense metastable atom traps. The degree of its suppression in a spin polarized gas will strongly affect the feasibility of a quantum-degenerate system of metastable atoms. In addition, metastable noble gas atoms will allow the implementation of novel diagnostics for the investigation of Bose condensates due to their high detectability. We want to make use of this advantage in order to investigate higher order correlation functions and study the laser-like behavior of Bose condensates and atom-laser outputs. We have achieved loading of 4/spl times/10/sup 8/ atoms in a magneto-optical trap (MOT) and after efficient spin polarization of 2.5 /spl times/ 10/sup 8/ atoms in a Ioffe-Pritchard-type magnetic trap. We present a precision measurement of the lifetime of the 3s[3/2]/sub 2/-metastable state of neon which we could determine to 14.70(13)s. We report on the status of the determination of the elastic scattering rate, the rates of Penning ionization for spin-polarized and non-spin-polarized atom samples, and the implementation of evaporative cooling.

European Quantum Electronics Conference (EQEC)Oct 19, 20040 citations

We investigate the relation between the thermalization cross section

{⟨\ensuremath{\sigma}⟩}_{T}

and the scattering length

a

of spin-polarized metastable neon

({\mathrm{Ne}}^{*})

in the Doppler-limited temperature regime. We show that a temperature-dependent, quantum-mechanical, five-channel calculation allows one to obtain

a

consistent with the mass scaling rule between

^{20}\mathrm{Ne}^{*}

and

^{22}\mathrm{Ne}^{*}

from recent data of

{⟨\ensuremath{\sigma}⟩}_{T}

by Spoden et al. [Phys. Rev. Lett. 94, 223201 (2005)]. We find

a=+{24}_{\ensuremath{-}5}^{+5}{a}_{0}

a=\ensuremath{-}{128}_{\ensuremath{-}22}^{+16}{a}_{0}

for

^{20}\mathrm{Ne}^{*}

and

+115\ensuremath{\lesssim}a\ensuremath{\lesssim}+160{a}_{0}

for

^{22}\mathrm{Ne}^{*}

, respectively. According to numerical simulations of the evaporative cooling process, these values of

a

are not large enough to make Bose-Einstein condensation of

{\mathrm{Ne}}^{*}

feasible for realistic experimental conditions, given the measured ionization rate constants.

In this paper we investigate the effective scattering length a of spin-polarized

{\mathrm{Ne}}^{*}.

Due to its anisotropic electrostatic interaction, its scattering length is determined by five interaction potentials instead of one, even in the spin-polarized case, a unique property among the Bose condensed species and candidates. Because the interaction potentials of

{\mathrm{Ne}}^{*}

are not known accurately enough to predict the value of the scattering length, we investigate the behavior of a as a function of the five phase integrals ${\ensuremath{\Phi}}_{\ensuremath{\Omega}}$ corresponding to the five interaction potentials. We find that the scattering length has five resonances instead of only one and cannot be described by a simple gas-kinetic approach or the degenerate internal state (DIS) approximation. However, the probability for finding a positive or large value of the scattering length is not enhanced compared to the single-potential case. We find that the induced dipole-dipole interaction enables strong coupling between the different $|J\ensuremath{\Omega}{\mathrm{PM}}_{P}〉$ states, resulting in an inhomogeneous shift of the resonance positions and widths in the quantum-mechanical calculation as compared to the DIS approach. The dependence of the resonance positions and widths on the input potentials turns out to be rather straightforward. The existence of two bosonic isotopes of

{\mathrm{Ne}}^{*}

enables us to choose the isotope with the most favorable scattering length for efficient evaporative cooling towards the Bose-Einstein condensation transition, greatly enhancing the feasibility to reach this transition.

The calculated upper limit ${\mathcal{K}}_{i}^{\mathrm{pol}}<~{10}^{\ensuremath{-}14}{\mathrm{cm}}^{3}/\mathrm{s}$ of the rate constant for suppressed ionization in a gas of metastable

\mathrm{Ne}{(}^{3}{\mathrm{P}}_{2})

atoms in the fully aligned

|{J=2,m}_{J}=2〉

state is used as input to investigate the prospects for achieving Bose-Einstein condensation (BEC). The heating rate of the trap population by secondary collisions of the hot products of the process of ionization---i.e., ground-state atoms, ions, and dimer-ions---with cold trapped metastable atoms is discussed in terms of a semiclassical model. An important step lies in limiting the depth of the magnetic trap to a value of a few millikelvin, to limit the range of small-angle scattering that contributes to heating. Also, a tight radial confinement reduces the probability for secondary collisions. At a trap depth of 10 mK, a radial dimension of $3\ensuremath{\mu}\mathrm{m},$ and a density of $2\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{cm}}^{\ensuremath{-}3}$ the heating rate is $1.4\ensuremath{\mu}\mathrm{K}/\mathrm{s},$ which should be compared to the transition temperature to BEC of $0.6\ensuremath{\mu}\mathrm{K}.$ The collisional heating is dominated by ion---metastable-atom collisions, due to their long-range charge-induced dipole interaction. Keeping the evaporative cooling switched on at

{T=T}_{C}

reduces the heating a hundredfold. Using a bright beam of laser cooled neon atoms, an initial population of

>~{10}^{10}

atoms can be loaded into a magneto-optical trap in one second. Tight magnetic traps are easy to achieve for metastable neon atoms, due to their magnetic moment of $3{\ensuremath{\mu}}_{B}.$ We conclude that achieving BEC is feasible for metastable neon. This also holds for triplet metastable helium, once the loading rate of traps has been improved. Finally, the semiclassical model used for calculating the heating rate is applicable to a wide range of inelastic collisions in trapped alkali gases and/or collisions with background gas.

We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable (

{}^{3}\phantom{\rule{-0.16em}{0ex}}{P}_{2}

) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes

{}^{20}

Ne,

{}^{21}

Ne, and

{}^{22}

Ne. We determine the rate coefficients for heteronuclear ionizing collisions to ${\ensuremath{\beta}}_{21,20}=(3.9\ifmmode\pm\else\textpm\fi{}2.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm

{}^{3}

/s, ${\ensuremath{\beta}}_{22,20}=(2.6\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm

{}^{3}

/s, and ${\ensuremath{\beta}}_{21,22}=(3.9\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm

{}^{3}

/s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state.