Helium atoms in the metastable $2^{3}S_{1}$ state ( ${\mathrm{He}}^{*}$ ) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in ${\mathrm{He}}^{*}$ which could be used to manipulate the scattering length and hence unlock several new experimental possibilities. Previous experimental and theoretical studies for ${\mathrm{He}}^{*}$ have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a close-coupled model of ${\mathrm{He}}^{*}$ collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally usable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.Helium atoms in the metastable $2^{3}S_{1}$ state (${\mathrm{He}}^{*}$) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in ${\mathrm{He}}^{*}$ which could be used to manipulate the scattering length and hence unlock several new experimental possibilities. Previous experimental and theoretical studies for ${\mathrm{He}}^{*}$ have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a close-coupled model of ${\mathrm{He}}^{*}$ collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally usable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.

arXiv:2105.12940Physical Review ASep 20, 20215 citations

Magnetic Feshbach resonances in collisions of closed-shell $^1\Sigma$ moleculesMagnetic Feshbach resonances in collisions of closed-shell $^1\Sigma$ molecules

Alisdair O. G. Wallis, Roman V. Krems

Magnetic Feshbach resonances play a central role in experimental research of atomic gases at ultracold temperatures, as they allow one to control the microscopic interactions between ultracold atoms by tuning an applied magnetic field. These resonances arise due to strong hyperfine interactions between the unpaired electron and the nuclear magnetic moment of the alkali metal atoms. A major thrust of current research is to create an ultracold gas of diatomic alkali-metal molecules in the ground rovibrational state of the ground electronic $^1\Sigma$ state. Unlike alkali metal atoms, $^1\Sigma$ diatomic molecules have no unpaired electrons. However, the hyperfine interactions of molecules may give rise to magnetic Feshbach resonances. We use quantum scattering calculations to study the possible width of these resonances. Our results show that the widths of magnetic Feshbach resonances in ultracold molecule-molecule collisions for $^1\Sigma$ molecules may exceed 1 milliGauss, rendering such resonances experimentally detectable. We hope that this work will stimulate the experimental search of these resonances.Magnetic Feshbach resonances play a central role in experimental research of atomic gases at ultracold temperatures, as they allow one to control the microscopic interactions between ultracold atoms by tuning an applied magnetic field. These resonances arise due to strong hyperfine interactions between the unpaired electron and the nuclear magnetic moment of the alkali metal atoms. A major thrust of current research is to create an ultracold gas of diatomic alkali-metal molecules in the ground rovibrational state of the ground electronic $^1\Sigma$ state. Unlike alkali metal atoms, $^1\Sigma$ diatomic molecules have no unpaired electrons. However, the hyperfine interactions of molecules may give rise to magnetic Feshbach resonances. We use quantum scattering calculations to study the possible width of these resonances. Our results show that the widths of magnetic Feshbach resonances in ultracold molecule-molecule collisions for $^1\Sigma$ molecules may exceed 1 milliGauss, rendering such resonances experimentally detectable. We hope that this work will stimulate the experimental search of these resonances.

Sep 6, 20120 citations

Magnetic Feshbach resonances in collisions of nonmagnetic closed-shell 1Σ molecules

Alisdair O. G. Wallis, Roman V. Krems

Magnetic Feshbach resonances play a central role in experimental research on atomic gases at ultracold temperatures, as they allow one to control the microscopic interactions between ultracold atoms by tuning an applied magnetic field. These resonances arise due to strong hyperfine interactions between the unpaired electron and the nuclear magnetic moment of the alkali metal atoms. A major thrust of current research is to create an ultracold gas of diatomic alkali metal molecules in the ground rovibrational state of the ground electronic ${}^{1}\ensuremath{\Sigma}$ state. Unlike alkali metal atoms, ${}^{1}\ensuremath{\Sigma}$ diatomic molecules have no unpaired electrons. However, the hyperfine interactions of molecules may give rise to magnetic Feshbach resonances. We use quantum scattering calculations to study the possible width of these resonances. Our results show that the widths of magnetic Feshbach resonances in ultracold molecule-molecule collisions for ${}^{1}\ensuremath{\Sigma}$ molecules may exceed 1 mG, rendering such resonances experimentally detectable. We hope that this work will stimulate the experimental search of these resonances.Magnetic Feshbach resonances play a central role in experimental research on atomic gases at ultracold temperatures, as they allow one to control the microscopic interactions between ultracold atoms by tuning an applied magnetic field. These resonances arise due to strong hyperfine interactions between the unpaired electron and the nuclear magnetic moment of the alkali metal atoms. A major thrust of current research is to create an ultracold gas of diatomic alkali metal molecules in the ground rovibrational state of the ground electronic ${}^{1}\ensuremath{\Sigma}$ state. Unlike alkali metal atoms, ${}^{1}\ensuremath{\Sigma}$ diatomic molecules have no unpaired electrons. However, the hyperfine interactions of molecules may give rise to magnetic Feshbach resonances. We use quantum scattering calculations to study the possible width of these resonances. Our results show that the widths of magnetic Feshbach resonances in ultracold molecule-molecule collisions for ${}^{1}\ensuremath{\Sigma}$ molecules may exceed 1 mG, rendering such resonances experimentally detectable. We hope that this work will stimulate the experimental search of these resonances.

arXiv:1209.1418Physical Review AMar 31, 20145 citations

Helium atoms in the metastable

2^{3}S_{1}

state (

{\mathrm{He}}^{*}

) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in

{\mathrm{He}}^{*}

which could be used to manipulate the scattering length and hence unlock several new experimental possibilities. Previous experimental and theoretical studies for

{\mathrm{He}}^{*}

have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a close-coupled model of

{\mathrm{He}}^{*}

collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally usable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.

Magnetic Feshbach resonances in collisions of closed-shell

^1\Sigma

molecules

^1\Sigma

state. Unlike alkali metal atoms,

^1\Sigma

diatomic molecules have no unpaired electrons. However, the hyperfine interactions of molecules may give rise to magnetic Feshbach resonances. We use quantum scattering calculations to study the possible width of these resonances. Our results show that the widths of magnetic Feshbach resonances in ultracold molecule-molecule collisions for

^1\Sigma

molecules may exceed 1 milliGauss, rendering such resonances experimentally detectable. We hope that this work will stimulate the experimental search of these resonances.