Photostabilization of ultracold Rb2 molecules by optimal control

Boris Schäfer-Bung, Roland Mitrić, Vlasta Bonačić‐Koutecký

Published Sep 25, 2006• 0 citations

OpenAlex

Abstract

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Photostabilization of the ultracold Rb2molecule by optimal control

Boris Schäfer-Bung, Roland Mitrić, Vlasta Bonačić‐Koutecký

Journal of Physics B Atomic Molecular and Optical PhysicsSep 25, 20066 citations

Vibrational stabilization of ultracold KRb molecules: A comparative study

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The transfer of weakly bound KRb molecules from levels just below the dissociation threshold into the vibrational ground state with shaped laser pulses is studied. Optimal control theory is employed to calculate the pulses. The complexity of modeling the molecular structure is successively increased in order to study the effects of the long-range behavior of the excited-state potential, resonant spin-orbit coupling, and singlet-triplet mixing.

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Stabilization of ultracold molecules using optimal control theory

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Dynamical interferences to probe short-pulse photoassociation of Rb atoms and stabilization of Rb2 dimers

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Enhancement of the formation of ultracold Rb285 molecules due to resonant coupling

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Utlracold Rb2 Molecules: Formation, Detection and Trapping in an Optical Dipole Trap

Hyewon Pechkis

Jan 1, 20100 citations

Photostabilization of ultracold Rb2 molecules by optimal control

Boris Schäfer-Bung, Roland Mitrić, Vlasta Bonačić‐Koutecký

Published Sep 25, 2006• 0 citations

OpenAlex

Abstract

Related papers

Photostabilization of the ultracold Rb2molecule by optimal control

Boris Schäfer-Bung, Roland Mitrić, Vlasta Bonačić‐Koutecký

We present a theoretical study of the photostabilization of the ultracold Rb 2 molecule by tailored laser fields. The simulations involve the ground and two excited electronic states, taking into account spin–orbit coupling, and are based on the full quantum mechanical optimal control theory. We demonstrate starting from a highly excited bound vibrational state that almost 100% population of the ground state v = 0 vibrational level can be achieved. The obtained optimal pulse has a long temporal and very broad spectral range. Our results reveal the mechanism of the photostabilization process and allow the proposal of new strategies for the formation of ultracold molecules taking into account the necessary constraints for possible experimental realization.We present a theoretical study of the photostabilization of the ultracold Rb 2 molecule by tailored laser fields. The simulations involve the ground and two excited electronic states, taking into account spin–orbit coupling, and are based on the full quantum mechanical optimal control theory. We demonstrate starting from a highly excited bound vibrational state that almost 100% population of the ground state v = 0 vibrational level can be achieved. The obtained optimal pulse has a long temporal and very broad spectral range. Our results reveal the mechanism of the photostabilization process and allow the proposal of new strategies for the formation of ultracold molecules taking into account the necessary constraints for possible experimental realization.

Journal of Physics B Atomic Molecular and Optical PhysicsSep 25, 20066 citations

Vibrational stabilization of ultracold KRb molecules: A comparative study

Mamadou Ndong, Christiane P. Koch

arXiv:1007.1898Physical Review AOct 29, 201028 citations

Stabilization of ultracold molecules using optimal control theory

Christiane P. Koch, José P. Palao, Ronnie Kosloff +1 more

In recent experiments on ultracold matter, molecules have been produced from ultracold atoms by photoassociation, Feshbach resonances, and three-body recombination. The created molecules are translationally cold, but vibrationally highly excited. This will eventually lead them to be lost from the trap due to collisions. We propose shaped laser pulses to transfer these highly excited molecules to their ground vibrational level. Optimal control theory is employed to find the light field that will carry out this task with minimum intensity. We present results for the sodium dimer. The final target can be reached to within $99%$ provided the initial guess field is physically motivated. We find that the optimal fields contain the transition frequencies required by a good Franck-Condon pumping scheme. The analysis identifies the ranges of intensity and pulse duration which are able to achieve this task before any other competing processes take place. Such a scheme could produce stable ultracold molecular samples or even stable molecular Bose-Einstein condensates.In recent experiments on ultracold matter, molecules have been produced from ultracold atoms by photoassociation, Feshbach resonances, and three-body recombination. The created molecules are translationally cold, but vibrationally highly excited. This will eventually lead them to be lost from the trap due to collisions. We propose shaped laser pulses to transfer these highly excited molecules to their ground vibrational level. Optimal control theory is employed to find the light field that will carry out this task with minimum intensity. We present results for the sodium dimer. The final target can be reached to within $99%$ provided the initial guess field is physically motivated. We find that the optimal fields contain the transition frequencies required by a good Franck-Condon pumping scheme. The analysis identifies the ranges of intensity and pulse duration which are able to achieve this task before any other competing processes take place. Such a scheme could produce stable ultracold molecular samples or even stable molecular Bose-Einstein condensates.

arXiv:quant-ph/0402066Physical Review AJul 7, 2004131 citations

Dynamical interferences to probe short-pulse photoassociation of Rb atoms and stabilization of Rb2 dimers

Jordi Mur-Petit, Eliane Luc-Koenig, Françoise Masnou-Seeuws

We analyze the formation of ${\mathrm{Rb}}_{2}$ molecules with short photoassociation pulses applied to a cold $^{85}\mathrm{Rb}$ sample. A pump laser pulse couples a continuum level of the ground electronic state $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ with bound levels in the ${0}_{u}^{+}(5S+5{P}_{1∕2})$ and ${0}_{u}^{+}(5S+5{P}_{3∕2})$ vibrational series. The nonadiabatic coupling between the two excited channels induces time-dependent beatings in the populations. We propose to take advantage of these oscillations to design further laser pulses that probe the photoassociation process via photoionization or that optimize the stabilization in deep levels of the ground state.We analyze the formation of ${\mathrm{Rb}}_{2}$ molecules with short photoassociation pulses applied to a cold $^{85}\mathrm{Rb}$ sample. A pump laser pulse couples a continuum level of the ground electronic state $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ with bound levels in the ${0}_{u}^{+}(5S+5{P}_{1∕2})$ and ${0}_{u}^{+}(5S+5{P}_{3∕2})$ vibrational series. The nonadiabatic coupling between the two excited channels induces time-dependent beatings in the populations. We propose to take advantage of these oscillations to design further laser pulses that probe the photoassociation process via photoionization or that optimize the stabilization in deep levels of the ground state.

arXiv:physics/0612143Physical Review AJun 21, 200717 citations

Enhancement of the formation of ultracold Rb285 molecules due to resonant coupling

Hyewon Pechkis, Dajun Wang, Yanyan Huang +4 more

We have studied the effect of resonant electronic-state coupling on the formation of ultracold ground-state $^{85}\mathrm{Rb}_{2}$ . Ultracold ${\mathrm{Rb}}_{2}$ molecules are formed by photoassociation (PA) to a coupled pair of ${0}_{u}^{+}$ states, ${0}_{u}^{+}({P}_{1∕2})$ and ${0}_{u}^{+}({P}_{3∕2})$ , in the region below the $5S+5{P}_{1∕2}$ limit. Subsequent radiative decay produces high vibrational levels of the ground state, $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$. The population distribution of these $X$ -state vibrational levels is monitored by resonance-enhanced two-photon ionization through the $2\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{u}^{+}$ state. We find that the populations of vibrational levels ${v}^{\ensuremath{''}}=112--116$ are far larger than can be accounted for by the Franck-Condon factors for ${0}_{u}^{+}({P}_{1∕2})\ensuremath{\rightarrow}X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ transitions with the ${0}_{u}^{+}({P}_{1∕2})$ state treated as a single channel. Further, the ground-state molecule population exhibits oscillatory behavior as the PA laser is tuned through a succession of ${0}_{u}^{+}$ state vibrational levels. Both of these effects are explained by a calculation of transition amplitudes that includes the resonant character of the spin-orbit coupling of the two ${0}_{u}^{+}$ states. The resulting enhancement of more deeply bound ground-state molecule formation will be useful for future experiments on ultracold molecules.We have studied the effect of resonant electronic-state coupling on the formation of ultracold ground-state $^{85}\mathrm{Rb}_{2}$. Ultracold ${\mathrm{Rb}}_{2}$ molecules are formed by photoassociation (PA) to a coupled pair of ${0}_{u}^{+}$ states, ${0}_{u}^{+}({P}_{1∕2})$ and ${0}_{u}^{+}({P}_{3∕2})$, in the region below the $5S+5{P}_{1∕2}$ limit. Subsequent radiative decay produces high vibrational levels of the ground state, $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$. The population distribution of these $X$-state vibrational levels is monitored by resonance-enhanced two-photon ionization through the $2\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{u}^{+}$ state. We find that the populations of vibrational levels ${v}^{\ensuremath{''}}=112--116$ are far larger than can be accounted for by the Franck-Condon factors for ${0}_{u}^{+}({P}_{1∕2})\ensuremath{\rightarrow}X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ transitions with the ${0}_{u}^{+}({P}_{1∕2})$ state treated as a single channel. Further, the ground-state molecule population exhibits oscillatory behavior as the PA laser is tuned through a succession of ${0}_{u}^{+}$ state vibrational levels. Both of these effects are explained by a calculation of transition amplitudes that includes the resonant character of the spin-orbit coupling of the two ${0}_{u}^{+}$ states. The resulting enhancement of more deeply bound ground-state molecule formation will be useful for future experiments on ultracold molecules.

arXiv:0707.2401Physical Review AAug 22, 200733 citations

Utlracold Rb2 Molecules: Formation, Detection and Trapping in an Optical Dipole Trap

Hyewon Pechkis

This thesis comprises two topics in the field of the ultracold atomic and molecular physics, both involving formation of ultracold 85Rb 2 by photoassociation (PA). Typically, these ground-state molecules are formed mainly in the very highest vibrational levels, rather than the low-v levels that will be required for most future investigations of ultracold molecular physics and chemistry. The first topic of my research is a method for circumventing this problem: resonant enhancement (RE) of photoassociative ground-state molecule production. The key idea of RE is to photoassociate pairs of colliding atoms into an excited state that has a bimodal vibrational probability distribution, with one peak at long range to enhance the photoassociation rate and another at shorter range to enhance radiative decay into deeply bound levels of the ground state. This can be arranged thanks to the strong spin-orbit perturbative interaction between the two 0+u states converging to two different asymptotes, (5s + 5p1/2) and (5s + 5 p3/2). This method enhances ground-state molecule formation in the region well below the dissociation limit. The experimental work described here was done at the University of Connecticut in collaboration with C. P. Koch at the Institut für Theoretische Physik, Freie Universität Berlin, Germany, who performed the theoretical analysis [1].^ The second part of my thesis is the investigation of ultracold molecules in an optical dipole trap. We have constructed a quasi-electrostratic optical trap (QUEST) for 85Rb using a focused CO2 laser [2]. This provides a very high density of ultracold atoms, up to 10 12 cm-3, providing much higher photoassociation rates. It also keeps the molecules trapped once they have formed. The QUEST provides an ample trapping lifetime for both trapped atoms and molecules, yielding about 4-5×106 atoms and about 9×105 high-v molecules. The long lifetime of the trapped molecules and atoms, combined with their high density, allows us to study interactions such as atom-molecule or molecule-molecule collisions in the ultracold regime. A preliminary experiment on Rb2 molecular decay is described. ^This thesis comprises two topics in the field of the ultracold atomic and molecular physics, both involving formation of ultracold 85Rb 2 by photoassociation (PA). Typically, these ground-state molecules are formed mainly in the very highest vibrational levels, rather than the low-v levels that will be required for most future investigations of ultracold molecular physics and chemistry. The first topic of my research is a method for circumventing this problem: resonant enhancement (RE) of photoassociative ground-state molecule production. The key idea of RE is to photoassociate pairs of colliding atoms into an excited state that has a bimodal vibrational probability distribution, with one peak at long range to enhance the photoassociation rate and another at shorter range to enhance radiative decay into deeply bound levels of the ground state. This can be arranged thanks to the strong spin-orbit perturbative interaction between the two 0+u states converging to two different asymptotes, (5s + 5p1/2) and (5s + 5 p3/2). This method enhances ground-state molecule formation in the region well below the dissociation limit. The experimental work described here was done at the University of Connecticut in collaboration with C. P. Koch at the Institut für Theoretische Physik, Freie Universität Berlin, Germany, who performed the theoretical analysis [1].^ The second part of my thesis is the investigation of ultracold molecules in an optical dipole trap. We have constructed a quasi-electrostratic optical trap (QUEST) for 85Rb using a focused CO2 laser [2]. This provides a very high density of ultracold atoms, up to 10 12 cm-3, providing much higher photoassociation rates. It also keeps the molecules trapped once they have formed. The QUEST provides an ample trapping lifetime for both trapped atoms and molecules, yielding about 4-5×106 atoms and about 9×105 high-v molecules. The long lifetime of the trapped molecules and atoms, combined with their high density, allows us to study interactions such as atom-molecule or molecule-molecule collisions in the ultracold regime. A preliminary experiment on Rb2 molecular decay is described. ^

Jan 1, 20100 citations

99%

provided the initial guess field is physically motivated. We find that the optimal fields contain the transition frequencies required by a good Franck-Condon pumping scheme. The analysis identifies the ranges of intensity and pulse duration which are able to achieve this task before any other competing processes take place. Such a scheme could produce stable ultracold molecular samples or even stable molecular Bose-Einstein condensates.

We analyze the formation of

{\mathrm{Rb}}_{2}

molecules with short photoassociation pulses applied to a cold

^{85}\mathrm{Rb}

sample. A pump laser pulse couples a continuum level of the ground electronic state $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ with bound levels in the

{0}_{u}^{+}(5S+5{P}_{1∕2})

and

{0}_{u}^{+}(5S+5{P}_{3∕2})

vibrational series. The nonadiabatic coupling between the two excited channels induces time-dependent beatings in the populations. We propose to take advantage of these oscillations to design further laser pulses that probe the photoassociation process via photoionization or that optimize the stabilization in deep levels of the ground state.

We have studied the effect of resonant electronic-state coupling on the formation of ultracold ground-state

^{85}\mathrm{Rb}_{2}

. Ultracold

{\mathrm{Rb}}_{2}

molecules are formed by photoassociation (PA) to a coupled pair of

{0}_{u}^{+}

states,

{0}_{u}^{+}({P}_{1∕2})

and

{0}_{u}^{+}({P}_{3∕2})

, in the region below the

5S+5{P}_{1∕2}

limit. Subsequent radiative decay produces high vibrational levels of the ground state, $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$. The population distribution of these

X

-state vibrational levels is monitored by resonance-enhanced two-photon ionization through the $2\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{u}^{+}$ state. We find that the populations of vibrational levels ${v}^{\ensuremath{''}}=112--116$ are far larger than can be accounted for by the Franck-Condon factors for ${0}_{u}^{+}({P}_{1∕2})\ensuremath{\rightarrow}X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ transitions with the

{0}_{u}^{+}({P}_{1∕2})

state treated as a single channel. Further, the ground-state molecule population exhibits oscillatory behavior as the PA laser is tuned through a succession of

{0}_{u}^{+}

state vibrational levels. Both of these effects are explained by a calculation of transition amplitudes that includes the resonant character of the spin-orbit coupling of the two

{0}_{u}^{+}

states. The resulting enhancement of more deeply bound ground-state molecule formation will be useful for future experiments on ultracold molecules.