Steering ultracold reactions through long-lived transient intermediates

Abstract

Controlling the pathways and outcomes of reactions is a broadly pursued goal in chemistry. In gas phase reactions, this is typically achieved by manipulating the properties of the reactants, including their translational energy, orientation, and internal quantum state. In contrast, here we influence the pathway of a reaction via its intermediate complex, which is generally too short-lived to be affected by external processes. In particular, the ultracold preparation of potassium-rubidium (KRb) reactants leads to a long-lived intermediate complex (K${}_2$Rb${}_2^{\ast }$), which allows us to steer the reaction away from its nominal ground-state pathway onto a newly identified excited-state pathway using a laser source at 1064 nm, a wavelength commonly used to confine ultracold molecules. Furthermore, by monitoring the change in the complex population after the sudden removal of the excitation light, we directly measure the lifetime of the complex to be $360\pm 30$ ns, in agreement with our calculations based on the Rice-Ramsperger-Kassel-Marcus (RRKM) statistical theory. Our results shed light on the origin of the two-body loss widely observed in ultracold molecule experiments. Additionally, the long complex lifetime, coupled with the observed photo-excitation pathway, opens up the possibility to spectroscopically probe the structure of the complex with high resolution, thus elucidating the reaction dynamics.

18 pages, 5 figures

References in corpus (26)

• Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules
• Condensed Matter Theory of Dipolar Quantum Gases
• Bose-Einstein condensation in trapped dipolar gases
• Dipolar collisions of polar molecules in the quantum regime
• Ultracold dense samples of dipolar RbCs molecules in the rovibrational and hyperfine ground state
• Strongly correlated 2D quantum phases with cold polar molecules: controlling the shape of the interaction potential
• Ultracold Dipolar Gas of Fermionic ${}^{23}$Na${}^{40}$K Molecules in their Absolute Ground State
• Controlling the quantum stereodynamics of ultracold bimolecular reactions
• A Fermi Degenerate Gas of Polar Molecules
• Direct observation of bimolecular reactions of ultracold KRb molecules
• Observation of magnetically tunable Feshbach resonances in ultracold ${}^{23}$Na${}^{40}$K+${}^{40}$K collisions
• Millikelvin Reactive Collisions between Sympathetically-Cooled Molecular Ions and Laser-Cooled Atoms in an Ion-Atom Hybrid Trap
• Direct Frequency Comb Measurement of OD + CO -> DOCO Kinetics
• Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances
• Photo-induced two-body loss of ultracold molecules
• Collisions of ultracold ^{23}Na^{87}Rb molecules with controlled chemical reactivities
• Sticky collisions of ultracold RbCs molecules
• Loss of ultracold RbCs molecules via optical excitation of long-lived two-body collision complexes
• A Quantum Dipolar Spin Liquid
• Topological p_x+ip_y Superfluid Phase of Fermionic Polar Molecules
• Photodissociation of ultracold diatomic strontium molecules with quantum state control
• A quasiclassical method for calculating the density of states of ultracold collision complexes
• Controlled state-to-state atom-exchange reaction in an ultracold atom-dimer mixture
• Structure and thermochemistry of K${}_2$Rb, KRb${}_2$ and K${}_2$Rb${}_2$
• Reaction kinetics of ultracold molecule-molecule collisions
• Probing ultracold chemistry using ion spectrometry

Cited by in corpus (15)

• Observation of Collisions between Two Ultracold Ground-State CaF Molecules
• Tuning of dipolar interactions and evaporative cooling in a three-dimensional molecular quantum gas
• Precision test of statistical dynamics with state-to-state ultracold chemistry
• State-to-state control of ultracold molecular reactions
• Probing photoinduced two-body loss of ultracold non-reactive bosonic ${}^{23}$Na${}^{87}$Rb and ${}^{23}$Na${}^{39}$K molecules
• A Feshbach resonance in collisions between ultracold ground state molecules
• Evidence for association of triatomic molecule in ultracold ${}^{23}$Na${}^{40}$K and ${}^{40}$K mixture
• Magnetic Feshbach resonances in collisions of ${}^{23}$Na${}^{40}$K with ${}^{40}$K
• Tune-out and magic wavelengths for ground-state ${}^{23}$Na${}^{40}$K molecules
• Unified model of ultracold molecular collisions
• Quantum spin state selectivity and magnetic tuning of ultracold chemical reactions of triplet alkali-metal dimers with alkali-metal atoms
• Stereodynamic control of cold rotationally inelastic CO + HD collisions
• Hyperfine-to-rotational energy transfer in ultracold atom-molecule collisions
• Observation of resonant dipolar collisions in ultracold ${}^{23}$Na${}^{87}$Rb rotational mixtures
• Understanding chemical reactions in a quantum degenerate gas of polar molecules via complex formation