Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Bulletin of the American Physical Society

Production of Ultracold Molecules with Chirped Nanosecond-Time-scale Pulses

J. L. Carini, Shimshon Kallush, Ronnie Kosloff, P. L. Gould

Published Jun 9, 2015• 1 citation
OpenAlex

Abstract

We present results on the effects of nanosecond-timescale frequency-chirped laser light on the formation of 87Rb2 ultracold ground-state molecules. We investigate these effects through photoassociation (PA) experiments and quantum mechanical simulations. The PA experiments show that at higher intensities, the positive chirps have a higher formation rate than the unchirped or negative linear chirps. The quantum mechanical simulations reveal the mechanism responsible for this enhancement. Contributions from stimulated emission cause the positive chirp to be the most efficient for molecule formation.

Related papers

Efficient Formation of Ultracold Molecules with Chirped Nanosecond Pulses

J. L. Carini, Shimshon Kallush, Ronnie Kosloff +1 more

We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted.

arXiv:1510.04672•The Journal of Physical Chemistry A•Dec 11, 2015•16 citations

Production of ultracold molecules with chirped nanosecond pulses: Evidence for coherent effects

J. L. Carini, J. A. Pechkis, C. E. Rogers +3 more

We use frequency-chirped light on the nanosecond time scale to produce ultracold ${}^{87}$Rb${}_{2}$ molecules in the lowest triplet state via the process of photoassociation. Comparing to quantum simulations of the molecular formation, we conclude that coherent stimulated emission plays an important role and is primarily responsible for the significant difference observed between positive and negative chirps.

arXiv:1210.6004•Physical Review A•Jan 2, 2013•17 citations

Enhancement of ultracold molecule formation by local control in the nanosecond regime

J. L. Carini, Shimshon Kallush, Ronnie Kosloff +1 more

We describe quantum simulations of ultracold 87 Rb 2 molecule formation using photoassociation (PA) with nanosecond-time-scale pulses of frequency chirped light. In particular, we compare the case of a linear chirp to one where the frequency evolution is optimized by local control (LC) of the phase, and find that LC can provide a significant enhancement. The resulting optimal frequency evolution corresponds to a rapid jump from the PA absorption resonance to a downward transition to a bound level of the lowest triplet state. We also consider the case of two frequencies and investigate interference effects. The assumed chirp parameters should be achievable with nanosecond pulse shaping techniques and are predicted to provide a significant enhancement over recent experiments with linear chirps.

New Journal of Physics•Feb 18, 2015•6 citations

Coherent Control of Trap-Loss Collisions and Molecule Formation with Frequency-Chirped Light

J. A. Pechkis

We present results on coherent control of ultracold trap-loss collisions and molecule formation using frequency-chirped light. The chirps, either positive or negative, sweep 1 GHz in 100 ns and are red-detuned below the D2 line in either 85Rb or 87Rb. The pulses are Gaussian and have a full-width at half-maximum (FWHM) of 40 ns. In our collision experiments, we demonstrate coherent control of ultracold 85Rb collisions using nonlinear (either concave-down or concave-up) frequency chirps in the region of pulse detunings where coherent collision blocking occurs. We attribute this to the excitation radius of the negative chirp following the excited-wavepacket trajectory. We find that this process is dependent on the nonlinearity of the negative chirp. Specifically, the concave-down negative chirp yields a higher value of the collisional loss rate constant β than those of the concave-up and linear negative chirps. For nonlinear positive chirps, we find no significant dependence of β on the nonlinearity of the chirp. Our measurements are supported by quantum mechanical simulations of the collisional process. ^ In our molecule formation experiments, we use resonantly-enhanced multi- photon ionization to directly detect ground-state 87Rb 2 formed though photoassociation (PA) by linearly frequency-chirped pulses and subsequent spontaneous decay. In particular, we measure the rates of formation (R) and photodestruction (Γ PD) for positive and negative frequency-chirped pulses, as well as for unchirped pulses. We find that the unchirped pulse yields higher values of both R and ΓPD than those of the positively-chirped pulse, whose values in turn are greater than those of the negatively-chirped pulse. Our results are important steps towards coherent control of ultracold ground-state molecule formation. ^

•Jan 1, 2010•0 citations

Enhancement of Ultracold Molecule Formation Using Shaped Nanosecond Frequency Chirps

J. L. Carini, Shimshon Kallush, Ronnie Kosloff +1 more

We demonstrate that judicious shaping of a nanosecond-time-scale frequency chirp can dramatically enhance the formation rate of ultracold (87)Rb(2) molecules. Starting with ultracold (87)Rb atoms, we apply pulses of frequency-chirped light to first photoassociate the atoms into excited molecules and then, later in the chirp, deexcite these molecules into a high vibrational level of the lowest triplet state a (3)Σ(u)(+). The enhancing chirp shape passes through the absorption and stimulated emission transitions relatively slowly, thus increasing their adiabaticity, but jumps quickly between them to minimize the effects of spontaneous emission. Comparisons with quantum simulations for various chirp shapes support this enhancement mechanism.

arXiv:1602.08026•Physical Review Letters•Oct 21, 2015•36 citations

Coherent control of cold-molecule formation through photoassociation using a chirped-pulsed-laser field

Jiří Vala, Olivier Dulieu, Françoise Masnou-Seeuws +2 more

Enhancement of the production of cold molecules via photoassociation is considered for the ${\mathrm{Cs}}_{2}$ system. The employment of chirped picosecond pulses is proposed and studied theoretically. The analysis is based on the ability to achieve impulsive excitation which is given by the ultracold initial conditions where the nuclei are effectively stationary during the interaction with a field. The appropriate theoretical framework is the coordinate-dependent two-level system. Matching the pulse parameters to the potentials and initial conditions results in full Rabi cycling between the electronic potentials. By chirping the laser pulse, adiabatic transfer leading to the population inversion from the ground to the excited state is possible in a broad and tunable range of internuclear distance. Numerical simulations based on solving the time-dependent Schr\"odinger equation (TDSE) were performed. The simulation of the photoassociation of ${\mathrm{Cs}}_{2}$ from the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ to the excited ${0}_{g}^{\ensuremath{-}}$ state under ultracold conditions verifies the qualitative picture. The ability to control the population transfer is employed to optimize molecular formation. Transfer of population to the excited ${0}_{g}^{\ensuremath{-}}$ surface leaves a void in the nuclear density of the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ surface. This void is either filled by thermal motion or by quantum ``pressure'' and it is the rate-determining step in the photoassociation. The spontaneous-emission process leading to cold-molecules is simulated by including an optical potential in the TDSE. Consequently, the rate of cold molecule formation in a pulsed mode is found to be larger than that obtained in a continuous-wave mode.

Physical Review A•Dec 12, 2000•107 citations
We present results on the effects of nanosecond-timescale frequency-chirped laser light on the formation of 87Rb2 ultracold ground-state molecules. We investigate these effects through photoassociation (PA) experiments and quantum mechanical simulations. The PA experiments show that at higher intensities, the positive chirps have a higher formation rate than the unchirped or negative linear chirps. The quantum mechanical simulations reveal the mechanism responsible for this enhancement. Contributions from stimulated emission cause the positive chirp to be the most efficient for molecule formation.
We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted.
We use frequency-chirped light on the nanosecond time scale to produce ultracold 87{}^{87}87Rb2{}_{2}2​ molecules in the lowest triplet state via the process of photoassociation. Comparing to quantum simulations of the molecular formation, we conclude that coherent stimulated emission plays an important role and is primarily responsible for the significant difference observed between positive and negative chirps.
We describe quantum simulations of ultracold 87 Rb 2 molecule formation using photoassociation (PA) with nanosecond-time-scale pulses of frequency chirped light. In particular, we compare the case of a linear chirp to one where the frequency evolution is optimized by local control (LC) of the phase, and find that LC can provide a significant enhancement. The resulting optimal frequency evolution corresponds to a rapid jump from the PA absorption resonance to a downward transition to a bound level of the lowest triplet state. We also consider the case of two frequencies and investigate interference effects. The assumed chirp parameters should be achievable with nanosecond pulse shaping techniques and are predicted to provide a significant enhancement over recent experiments with linear chirps.
We present results on coherent control of ultracold trap-loss collisions and molecule formation using frequency-chirped light. The chirps, either positive or negative, sweep 1 GHz in 100 ns and are red-detuned below the D2 line in either 85Rb or 87Rb. The pulses are Gaussian and have a full-width at half-maximum (FWHM) of 40 ns. In our collision experiments, we demonstrate coherent control of ultracold 85Rb collisions using nonlinear (either concave-down or concave-up) frequency chirps in the region of pulse detunings where coherent collision blocking occurs. We attribute this to the excitation radius of the negative chirp following the excited-wavepacket trajectory. We find that this process is dependent on the nonlinearity of the negative chirp. Specifically, the concave-down negative chirp yields a higher value of the collisional loss rate constant β than those of the concave-up and linear negative chirps. For nonlinear positive chirps, we find no significant dependence of β on the nonlinearity of the chirp. Our measurements are supported by quantum mechanical simulations of the collisional process. ^ In our molecule formation experiments, we use resonantly-enhanced multi- photon ionization to directly detect ground-state 87Rb 2 formed though photoassociation (PA) by linearly frequency-chirped pulses and subsequent spontaneous decay. In particular, we measure the rates of formation (R) and photodestruction (Γ PD) for positive and negative frequency-chirped pulses, as well as for unchirped pulses. We find that the unchirped pulse yields higher values of both R and ΓPD than those of the positively-chirped pulse, whose values in turn are greater than those of the negatively-chirped pulse. Our results are important steps towards coherent control of ultracold ground-state molecule formation. ^
We demonstrate that judicious shaping of a nanosecond-time-scale frequency chirp can dramatically enhance the formation rate of ultracold (87)Rb(2) molecules. Starting with ultracold (87)Rb atoms, we apply pulses of frequency-chirped light to first photoassociate the atoms into excited molecules and then, later in the chirp, deexcite these molecules into a high vibrational level of the lowest triplet state a (3)Σ(u)(+). The enhancing chirp shape passes through the absorption and stimulated emission transitions relatively slowly, thus increasing their adiabaticity, but jumps quickly between them to minimize the effects of spontaneous emission. Comparisons with quantum simulations for various chirp shapes support this enhancement mechanism.
Enhancement of the production of cold molecules via photoassociation is considered for the Cs2{\mathrm{Cs}}_{2}Cs2​ system. The employment of chirped picosecond pulses is proposed and studied theoretically. The analysis is based on the ability to achieve impulsive excitation which is given by the ultracold initial conditions where the nuclei are effectively stationary during the interaction with a field. The appropriate theoretical framework is the coordinate-dependent two-level system. Matching the pulse parameters to the potentials and initial conditions results in full Rabi cycling between the electronic potentials. By chirping the laser pulse, adiabatic transfer leading to the population inversion from the ground to the excited state is possible in a broad and tunable range of internuclear distance. Numerical simulations based on solving the time-dependent Schr\"odinger equation (TDSE) were performed. The simulation of the photoassociation of Cs2{\mathrm{Cs}}_{2}Cs2​ from the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ to the excited ${0}_{g}^{\ensuremath{-}}$ state under ultracold conditions verifies the qualitative picture. The ability to control the population transfer is employed to optimize molecular formation. Transfer of population to the excited ${0}_{g}^{\ensuremath{-}}$ surface leaves a void in the nuclear density of the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ surface. This void is either filled by thermal motion or by quantum ``pressure'' and it is the rate-determining step in the photoassociation. The spontaneous-emission process leading to cold-molecules is simulated by including an optical potential in the TDSE. Consequently, the rate of cold molecule formation in a pulsed mode is found to be larger than that obtained in a continuous-wave mode.