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A quantum degenerate mixture of ⁸⁷Rb and ¹³³Cs

Daniel McCarron

Published Jan 1, 2011• 0 citations
OpenAlex

Abstract

This thesis reports the formation of a dual-species Bose-Einstein condensate of $^{87}$Rb and $^{133}$Cs in the same trapping potential. Quantum degenerate mixtures exhibit rich physics inaccessible to single species experiments and provide an ideal starting point for the creation of ultracold dipolar molecules. These molecules offer a wealth of new research avenues including precision metrology, quantum simulation and computation. The experimental method exploits the efficient sympathetic cooling of $^{133}$Cs via elastic collisions with $^{87}$Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. Evaporative cooling in the dipole trap must compete against a high interspecies three-body inelastic collision rate \mbox{$\sim10^{-25}-10^{-26}$~cm$^{6}/$s}. The two condensates each contain up to \mbox{$2\times10^{4}$} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the $^{87}$Rb during the cooling leads to the creation of single-species $^{133}$Cs condensates of up to \mbox{$6\times10^{4}$} atoms. In addition this thesis reports the observation of an interspecies Feshbach resonance at 181.7(5)~G and the creation of a pure sample of Cs$_{2}$ molecules via magneto-association on the 4(g)4 resonance at 19.8~G. These results represent important steps towards the creation of ultracold polar RbCs molecules.

Related papers

Dual-species Bose-Einstein condensate of Rb87 and Cs133

Daniel McCarron, H. W. Cho, Daniel L. Jenkin +2 more

We report the formation of a dual-species Bose-Einstein condensate of $^{87}\mathrm{Rb}$ and $^{133}\mathrm{Cs}$ in the same trapping potential. Our method exploits the efficient sympathetic cooling of $^{133}\mathrm{Cs}$ via elastic collisions with $^{87}\mathrm{Rb}$, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the $^{87}\mathrm{Rb}$ during the cooling, we create single-species $^{133}\mathrm{Cs}$ condensates of up to $6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms.

arXiv:1102.1576•Physical Review A•Jul 13, 2011•232 citations

Feshbach spectroscopy of an ultracold Rb-Cs mixture

Daniel L. Jenkin

This thesis reports the observation of interspecies Feshbach resonances in an ultracold mixture of Rb and Cs atoms. A versatile combined magnetic and optical potential has been designed and constructed which is capable of bringing both $^{87}\rm{Rb}$ and $^{133}\rm{Cs}$ to degeneracy, and reaching high phase-space density in $^{85}\rm{Rb}$. High phase-space density mixtures are the first step required in the production of ultracold polar molecules, the topic of much current research. The apparatus capitalises on the efficient capture of atoms by a magnetic trap from a magneto-optical trap, and the efficient sympathetic cooling of Cs by Rb therein. Upon transfer to the crossed optical dipole trap condensates in excess of $1\times10^{6}$ $^{87}\rm{Rb}$ atoms and approximately $1\times10^{5}$ $^{133}\rm{Cs}$ atoms are produced after direct evaporation and gravito-magnetic tilting of the potential. The observation of six interspecies $^{87}\rm{Rb}$-$^{133}\rm{Cs}$ Feshbach resonances are reported, three of which had only been predicted theoretically, allowing testing and development of the theoretical model. Furthermore, the extrapolation of this model has predicted numerous Feshbach resonances between $^{85}\rm{Rb}$ and $^{133}\rm{Cs}$, none of which have been experimentally observed prior to this work. The versatile nature of this apparatus is discussed, including the application of the current system to cooling of $^{85}\rm{Rb}$. Initial experiments observed seven interspecies resonances, including a broad s-wave resonance at a magnetic field of $(644\pm2)$ G which is in excellent agreement with the theoretical prediction. Further work has revealed that fourteen Feshbach resonances exist in the 0-700 G magnetic field range between $^{85}\rm{Rb}$ and $^{133}\rm{Cs}$ atoms in the $\left|2,+2\right\rangle$ and $\left|3,+3\right\rangle$ states, respectively. Several of these resonances would be ideal for magneto-association of RbCs molecules, prior to transfer to the rovibrational ground-state.

•Jan 1, 2012•0 citations

Quantum degenerate mixtures of 23Na-39K and coherent transfer paths in NaK molecules

Torben Schulze

The discovery and development of methods to cool, trap and manipulate atomic ensembles have generated a revolution in atomic physics, culminating in the ever expanding research field of ultra-cold matter through the realization of Bose-Einstein condensates (BECs). Since the first realization of BEC more than two decades ago, the majority of studies were concerned with systems displaying short-range contact interaction. Following pioneering experiments in ultra-cold KRb, systems involving ultra-cold mixtures have rose to considerable interest through their capability to form diatomic polar molecules. The long-range character of dipolar particle interactions enables the study of a whole new spectrum of quantum many-body phenomena by giving access to the strongly correlated regime. In this context, NaK is a splendid candidate to investigate dipolar effects due to its large electric dipole moment of $2.72 \, $Debye, its chemical stability and the large history of spectroscopic studies devoted to its ground and excited state manifolds. This thesis reports on the first ever realization of a dual-species degenerate mixture of $^{23}\mathrm{Na}$ and $^{39}\mathrm{K}$. The experimental apparatus combines two pre-cooled atomic sources into a UHV collection region, where a two-color magneto-optical trap is operated. After transferring both species into an optically plugged quadrupole trap, the $^{23}\mathrm{Na}$ ensemble is cooled by selectively removing the hottest atoms from the trap through microwave transitions, while $^{39}\mathrm{K}$ is sympathetically cooled through its thermal contact to $^{23}\mathrm{Na}$. Following the transfer into an optical dipole trap, the mixture operation suffers from strong losses as the atomic clouds approach the high-density regime. Interspecies interactions are identified as the system parameter that drives the loss mechanism. In order to realize a quantum degenerate mixture, the dual-species collisional properties are investigated both theoretically and experimentally. By preparing both optically trapped ensembles in the spin state $|f=1,m_{f}=-1\rangle$, atom loss spectroscopy is performed in a magnetic field range from $0$ to $1000 \, \mathrm{G}$. The observed features include several s-wave poles and a zero crossing of the interspecies scattering length as well as inelastic two-body contributions in the $\mathcal{M} = m_{\mathrm{Na}}+m_{\mathrm{K}} = -2$ submanifold. Different magnetic field regions are identified for the purposes of sympathetic cooling of $^{39}\mathrm{K}$ and achieving a quantum degenerate mixture. Forced evaporation creates two Bose-Einstein condensates simultaneously at a magnetic field that provides sizable intra- and interspecies scattering rates needed for fast thermalization. The impact of the differential gravitational sag on the miscibility criterion for the mixture is discussed. The experimental setup and measurements are complemented by theoretical calculations that form a feasibility study of molecular NaK. Starting from ultra-cold Feshbach molecules, the study demonstrates possible pathways for the creation of ultra-cold polar NaK molecules in their absolute electronic and rovibrational ground state. In particular, a multi-channel analysis of the electronic ground and K(4p)+Na(3s) excited state manifold of NaK is presented. It analyzes the spin character of both the Feshbach molecular state and the electronically excited intermediate states and discusses possible coherent two-photon transfer paths from Feshbach molecules to rovibronic ground state molecules. %The theoretical study is complemented by the demonstration of STIRAP transfer from the X1Σ+(v=0) state to the a3Σ+ manifold on a molecular beam experiment. The experimental results serve as a promising starting point for the magnetoassociation into quantum degenerate $^{23}\mathrm{Na}^{39}\mathrm{K}$ Feshbach molecules. The theoretical analysis assures qualitative understanding as well as quantitative statements for the feasibility of the subsequent ground state conversion. In combination, they fill a critical gap towards the creation of chemically stable ultra-cold molecular Bose-Einstein condensates of NaK.

•Jan 1, 2018•5 citations

Creation of ultracold RbCs molecules

Michael P. Köppinger

This thesis reports the investigation of the scattering properties of a mixture of Rb and Cs and the formation of ultracold Feshbach molecules. The production of Feshbach molecules is a crucial step towards the production of ultracold polar molecules, which is of significant interest for a wide range of potential applications. We have investigated the scattering properties of a mixture of $^{85}$Rb and $^{133}$Cs in their lowest spin channel in a magnetic field range from 0 to 700\,G. Furthermore, we explored the Feshbach spectrum of $^{85}$Rb alone in both, the $(f=2,m_f=-2)$ and $(2,+2)$ states up to a magnetic field of 1000\,G. Additionally a Feshbach resonance in a $(2,+2)+(3,+3)$ spin mixture was experimentally confirmed. We associated Cs$_2$ Feshbach molecules using a Feshbach resonance at 19.9\,G. \mbox{$2.1(1) \times 10^4$} molecules with a temperature of $\sim60$\,nK were produced from a sample of $3.28(2) \times 10^5$ Cs atoms with a PSD of 0.20(1). Due to a magnetic field gradient, the molecules `bounce' at an avoided crossing between two states at 13.5\,G. This gradient field was also used to produce multiple molecular clouds from one atomic sample. A combination of both techniques led to a `collision' between two Cs$_2$ clouds. Furthermore, we associated up to $\sim5000$ heteronuclear $^{87}$RbCs Feshbach molecules using an interspecies resonance at 197.1\,G. Confined in the dipole trap the molecules have a lifetime of 0.21(1)\,s. We have measured the magnetic moment of the molecules in different internal states in a magnetic field range from 181 to 185\,G. Molecular loss spectroscopy on electronically excited states was performed to identify candidates for the intermediate state of a STIRAP transfer of the molecules into their rovibrational ground state. Subsequently, the binding energy of the rovibrational ground state was measured to be 3811.574(1)\,cm$^{-1}$, using two-photon spectroscopy.

•Jan 1, 2014•2 citations

Dual-species Bose-Einstein condensates of $^{23}$Na and $^{41}$K with tunable interactions

Jaeryeong Chang, Sung‐Jun Lee, Yoonsoo Kim +2 more

We report the creation of dual-species Bose-Einstein condensates (BECs) of $^{23}$Na and $^{41}$K. Favorable background scattering lengths enable efficient sympathetic cooling of $^{41}$K via forced evaporative cooling of $^{23}$Na in a plugged magnetic trap and an optical dipole trap. The $1/e$ lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about $3\times10^5$ $^{23}$Na atoms surrounding $5\times10^4$ $^{41}$K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest $s$-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic $^{23}$Na$^{41}$K molecules as well as the exploration of many-body physics in bosonic $^{23}$Na-$^{41}$K mixtures.

arXiv:2312.08186•Dec 13, 2023•0 citations

Feshbach spectroscopy and dual-species Bose-Einstein condensation of Na23−K39 mixtures

Torben Schulze, Torsten Hartmann, Kai K. Voges +4 more

We present measurements of interspecies Feshbach resonances and subsequent creation of dual-species Bose-Einstein condensates of $^{23}\mathrm{Na}$ and $^{39}\mathrm{K}$. We prepare both optically trapped ensembles in the spin state $\left|f=1,{m}_{f}=\ensuremath{-}1\right\ensuremath{\rangle}$ and perform atom loss spectroscopy in a magnetic field range from $0$ to $700\phantom{\rule{0.16em}{0ex}}\mathrm{G}$. The observed features include several $s$-wave poles and a zero crossing of the interspecies scattering length as well as inelastic two-body contributions in the $\mathcal{M}={m}_{\mathrm{Na}}+{m}_{\mathrm{K}}=\ensuremath{-}2$ submanifold. We identify and discuss the suitability of different magnetic field regions for the purposes of sympathetic cooling of $^{39}\mathrm{K}$ and achieving dual-species degeneracy. Two condensates are created simultaneously by evaporation at a magnetic field of about $150\phantom{\rule{0.16em}{0ex}}\mathrm{G}$, which provides sizable intra- and interspecies scattering rates needed for fast thermalization. The impact of the differential gravitational sag on the miscibility criterion for the mixture is discussed. Our results serve as a promising starting point for the magnetoassociation into quantum degenerate $^{23}\mathrm{Na}^{39}\mathrm{K}$ Feshbach molecules.

arXiv:1709.03796•Physical Review A•Feb 13, 2018•45 citations
This thesis reports the formation of a dual-species Bose-Einstein condensate of 87^{87}87Rb and 133^{133}133Cs in the same trapping potential. Quantum degenerate mixtures exhibit rich physics inaccessible to single species experiments and provide an ideal starting point for the creation of ultracold dipolar molecules. These molecules offer a wealth of new research avenues including precision metrology, quantum simulation and computation. The experimental method exploits the efficient sympathetic cooling of 133^{133}133Cs via elastic collisions with 87^{87}87Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. Evaporative cooling in the dipole trap must compete against a high interspecies three-body inelastic collision rate \mbox{∼10−25−10−26\sim10^{-25}-10^{-26}∼10−25−10−26~cm6/^{6}/6/s}. The two condensates each contain up to \mbox{2×1042\times10^{4}2×104} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the 87^{87}87Rb during the cooling leads to the creation of single-species 133^{133}133Cs condensates of up to \mbox{6×1046\times10^{4}6×104} atoms. In addition this thesis reports the observation of an interspecies Feshbach resonance at 181.7(5)G and the creation of a pure sample of Cs2_{2}2​ molecules via magneto-association on the 4(g)4 resonance at 19.8G. These results represent important steps towards the creation of ultracold polar RbCs molecules.
We report the formation of a dual-species Bose-Einstein condensate of 87Rb^{87}\mathrm{Rb}87Rb and 133Cs^{133}\mathrm{Cs}133Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of 133Cs^{133}\mathrm{Cs}133Cs via elastic collisions with 87Rb^{87}\mathrm{Rb}87Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the 87Rb^{87}\mathrm{Rb}87Rb during the cooling, we create single-species 133Cs^{133}\mathrm{Cs}133Cs condensates of up to $6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms.
This thesis reports the observation of interspecies Feshbach resonances in an ultracold mixture of Rb and Cs atoms. A versatile combined magnetic and optical potential has been designed and constructed which is capable of bringing both 87Rb^{87}\rm{Rb}87Rb and 133Cs^{133}\rm{Cs}133Cs to degeneracy, and reaching high phase-space density in 85Rb^{85}\rm{Rb}85Rb. High phase-space density mixtures are the first step required in the production of ultracold polar molecules, the topic of much current research. The apparatus capitalises on the efficient capture of atoms by a magnetic trap from a magneto-optical trap, and the efficient sympathetic cooling of Cs by Rb therein. Upon transfer to the crossed optical dipole trap condensates in excess of 1×1061\times10^{6}1×106 87Rb^{87}\rm{Rb}87Rb atoms and approximately 1×1051\times10^{5}1×105 133Cs^{133}\rm{Cs}133Cs atoms are produced after direct evaporation and gravito-magnetic tilting of the potential. The observation of six interspecies 87Rb^{87}\rm{Rb}87Rb-133Cs^{133}\rm{Cs}133Cs Feshbach resonances are reported, three of which had only been predicted theoretically, allowing testing and development of the theoretical model. Furthermore, the extrapolation of this model has predicted numerous Feshbach resonances between 85Rb^{85}\rm{Rb}85Rb and 133Cs^{133}\rm{Cs}133Cs, none of which have been experimentally observed prior to this work. The versatile nature of this apparatus is discussed, including the application of the current system to cooling of 85Rb^{85}\rm{Rb}85Rb. Initial experiments observed seven interspecies resonances, including a broad s-wave resonance at a magnetic field of (644±2)(644\pm2)(644±2) G which is in excellent agreement with the theoretical prediction. Further work has revealed that fourteen Feshbach resonances exist in the 0-700 G magnetic field range between 85Rb^{85}\rm{Rb}85Rb and 133Cs^{133}\rm{Cs}133Cs atoms in the ∣2,+2⟩\left|2,+2\right\rangle∣2,+2⟩ and ∣3,+3⟩\left|3,+3\right\rangle∣3,+3⟩ states, respectively. Several of these resonances would be ideal for magneto-association of RbCs molecules, prior to transfer to the rovibrational ground-state.
The discovery and development of methods to cool, trap and manipulate atomic ensembles have generated a revolution in atomic physics, culminating in the ever expanding research field of ultra-cold matter through the realization of Bose-Einstein condensates (BECs). Since the first realization of BEC more than two decades ago, the majority of studies were concerned with systems displaying short-range contact interaction. Following pioneering experiments in ultra-cold KRb, systems involving ultra-cold mixtures have rose to considerable interest through their capability to form diatomic polar molecules. The long-range character of dipolar particle interactions enables the study of a whole new spectrum of quantum many-body phenomena by giving access to the strongly correlated regime. In this context, NaK is a splendid candidate to investigate dipolar effects due to its large electric dipole moment of $2.72 \, $Debye, its chemical stability and the large history of spectroscopic studies devoted to its ground and excited state manifolds. This thesis reports on the first ever realization of a dual-species degenerate mixture of 23Na^{23}\mathrm{Na}23Na and 39K^{39}\mathrm{K}39K. The experimental apparatus combines two pre-cooled atomic sources into a UHV collection region, where a two-color magneto-optical trap is operated. After transferring both species into an optically plugged quadrupole trap, the 23Na^{23}\mathrm{Na}23Na ensemble is cooled by selectively removing the hottest atoms from the trap through microwave transitions, while 39K^{39}\mathrm{K}39K is sympathetically cooled through its thermal contact to 23Na^{23}\mathrm{Na}23Na. Following the transfer into an optical dipole trap, the mixture operation suffers from strong losses as the atomic clouds approach the high-density regime. Interspecies interactions are identified as the system parameter that drives the loss mechanism. In order to realize a quantum degenerate mixture, the dual-species collisional properties are investigated both theoretically and experimentally. By preparing both optically trapped ensembles in the spin state ∣f=1,mf=−1⟩|f=1,m_{f}=-1\rangle∣f=1,mf​=−1⟩, atom loss spectroscopy is performed in a magnetic field range from 000 to 1000 G1000 \, \mathrm{G}1000G. The observed features include several s-wave poles and a zero crossing of the interspecies scattering length as well as inelastic two-body contributions in the M=mNa+mK=−2\mathcal{M} = m_{\mathrm{Na}}+m_{\mathrm{K}} = -2M=mNa​+mK​=−2 submanifold. Different magnetic field regions are identified for the purposes of sympathetic cooling of 39K^{39}\mathrm{K}39K and achieving a quantum degenerate mixture. Forced evaporation creates two Bose-Einstein condensates simultaneously at a magnetic field that provides sizable intra- and interspecies scattering rates needed for fast thermalization. The impact of the differential gravitational sag on the miscibility criterion for the mixture is discussed. The experimental setup and measurements are complemented by theoretical calculations that form a feasibility study of molecular NaK. Starting from ultra-cold Feshbach molecules, the study demonstrates possible pathways for the creation of ultra-cold polar NaK molecules in their absolute electronic and rovibrational ground state. In particular, a multi-channel analysis of the electronic ground and K(4p)+Na(3s) excited state manifold of NaK is presented. It analyzes the spin character of both the Feshbach molecular state and the electronically excited intermediate states and discusses possible coherent two-photon transfer paths from Feshbach molecules to rovibronic ground state molecules. %The theoretical study is complemented by the demonstration of STIRAP transfer from the X1Σ+(v=0) state to the a3Σ+ manifold on a molecular beam experiment. The experimental results serve as a promising starting point for the magnetoassociation into quantum degenerate 23Na39K^{23}\mathrm{Na}^{39}\mathrm{K}23Na39K Feshbach molecules. The theoretical analysis assures qualitative understanding as well as quantitative statements for the feasibility of the subsequent ground state conversion. In combination, they fill a critical gap towards the creation of chemically stable ultra-cold molecular Bose-Einstein condensates of NaK.
This thesis reports the investigation of the scattering properties of a mixture of Rb and Cs and the formation of ultracold Feshbach molecules. The production of Feshbach molecules is a crucial step towards the production of ultracold polar molecules, which is of significant interest for a wide range of potential applications. We have investigated the scattering properties of a mixture of 85^{85}85Rb and 133^{133}133Cs in their lowest spin channel in a magnetic field range from 0 to 700\,G. Furthermore, we explored the Feshbach spectrum of 85^{85}85Rb alone in both, the (f=2,mf=−2)(f=2,m_f=-2)(f=2,mf​=−2) and (2,+2)(2,+2)(2,+2) states up to a magnetic field of 1000\,G. Additionally a Feshbach resonance in a (2,+2)+(3,+3)(2,+2)+(3,+3)(2,+2)+(3,+3) spin mixture was experimentally confirmed. We associated Cs2_22​ Feshbach molecules using a Feshbach resonance at 19.9\,G. \mbox{2.1(1)×1042.1(1) \times 10^42.1(1)×104} molecules with a temperature of ∼60\sim60∼60\,nK were produced from a sample of 3.28(2)×1053.28(2) \times 10^53.28(2)×105 Cs atoms with a PSD of 0.20(1). Due to a magnetic field gradient, the molecules `bounce' at an avoided crossing between two states at 13.5\,G. This gradient field was also used to produce multiple molecular clouds from one atomic sample. A combination of both techniques led to a `collision' between two Cs2_22​ clouds. Furthermore, we associated up to ∼5000\sim5000∼5000 heteronuclear 87^{87}87RbCs Feshbach molecules using an interspecies resonance at 197.1\,G. Confined in the dipole trap the molecules have a lifetime of 0.21(1)\,s. We have measured the magnetic moment of the molecules in different internal states in a magnetic field range from 181 to 185\,G. Molecular loss spectroscopy on electronically excited states was performed to identify candidates for the intermediate state of a STIRAP transfer of the molecules into their rovibrational ground state. Subsequently, the binding energy of the rovibrational ground state was measured to be 3811.574(1)\,cm−1^{-1}−1, using two-photon spectroscopy.
Dual-species Bose-Einstein condensates of 23^{23}23Na and 41^{41}41K with tunable interactions
We report the creation of dual-species Bose-Einstein condensates (BECs) of 23^{23}23Na and 41^{41}41K. Favorable background scattering lengths enable efficient sympathetic cooling of 41^{41}41K via forced evaporative cooling of 23^{23}23Na in a plugged magnetic trap and an optical dipole trap. The 1/e1/e1/e lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about 3×1053\times10^53×105 23^{23}23Na atoms surrounding 5×1045\times10^45×104 41^{41}41K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest sss-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic 23^{23}23Na41^{41}41K molecules as well as the exploration of many-body physics in bosonic 23^{23}23Na-41^{41}41K mixtures.
We present measurements of interspecies Feshbach resonances and subsequent creation of dual-species Bose-Einstein condensates of 23Na^{23}\mathrm{Na}23Na and 39K^{39}\mathrm{K}39K. We prepare both optically trapped ensembles in the spin state $\left|f=1,{m}_{f}=\ensuremath{-}1\right\ensuremath{\rangle}$ and perform atom loss spectroscopy in a magnetic field range from 000 to 700G700\phantom{\rule{0.16em}{0ex}}\mathrm{G}700G. The observed features include several sss-wave poles and a zero crossing of the interspecies scattering length as well as inelastic two-body contributions in the $\mathcal{M}={m}_{\mathrm{Na}}+{m}_{\mathrm{K}}=\ensuremath{-}2$ submanifold. We identify and discuss the suitability of different magnetic field regions for the purposes of sympathetic cooling of 39K^{39}\mathrm{K}39K and achieving dual-species degeneracy. Two condensates are created simultaneously by evaporation at a magnetic field of about 150G150\phantom{\rule{0.16em}{0ex}}\mathrm{G}150G, which provides sizable intra- and interspecies scattering rates needed for fast thermalization. The impact of the differential gravitational sag on the miscibility criterion for the mixture is discussed. Our results serve as a promising starting point for the magnetoassociation into quantum degenerate 23Na39K^{23}\mathrm{Na}^{39}\mathrm{K}23Na39K Feshbach molecules.