Reaction blockading in a reaction between an excited atom and a charged molecule at low collision energy

Puri, Prateek; Mills, Michael D.; Simbotin, I.; Montgomery, John A.; Côté, Robin; Schneider, Christian; Suits, Arthur G.; Hudson, Eric R.

doi:10.1038/s41557-019-0264-3

Cited by 54 publications

(31 citation statements)

References 47 publications

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“…In the case of atoms isoelectronic to Yb, such as Ca, Sr, Ba, and Hg, excitation of reactants to metastable states was used for molecular spectroscopy [28,29] and investigations of reactions in ovens or beams with gases such as SF 6 [19,30], H 2 [30,31] [35,36], alcohols [19,32,34], halogens [19,30], halogenated alkanes [19,31,[37][38][39], and hydrogen halides [19,30,37,40,41]. More recently, the ability to trap and cool species to ultracold temperatures has enabled research of reaction dynamics between excited ions, atoms, and molecules [27,[42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry

et al. 2020

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We use narrow-band laser excitation of Yb atoms to substantially enhance the brightness of a cold beam of YbOH, a polyatomic molecule with high sensitivity to physics beyond the standard model (BSM). By exciting atomic Yb to the metastable 3 P 1 state in a cryogenic environment, we significantly increase the chemical reaction cross-section for collisions of Yb with reactants. We characterize the dependence of the enhancement on the properties of the laser light, and study the final state distribution of the YbOH products. The resulting bright, cold YbOH beam can be used to increase the statistical sensitivity in searches for new physics utilizing YbOH, such as electron electric dipole moment and nuclear magnetic quadrupole moment experiments. We also perform new quantum chemical calculations that confirm the enhanced reactivity observed in our experiment and compare reaction pathways of Yb( 3 P) with the reactants H 2 O and H 2 O 2 . More generally, our work presents a broad approach for improving experiments that use cryogenic molecular beams for laser cooling and precision measurement searches of BSM physics.

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Section: Introductionmentioning

confidence: 99%

Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry

et al. 2020

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“…The reaction rate for the Ca( 1 P) state is found to decrease with decreasing temperature in the range 0.3 -2 K, contrary to the predictions of capture theory, and the reaction is suppressed. In this case, the radiative lifetime of the excited Ca * quantum state was found to play a key role in governing the observed reaction rate 128 . A theoretical model allows us to calculate the time necessary for the reactants to form the collision complex.…”

Section: From 1 K Down To a Few Mkmentioning

confidence: 93%

Towards chemistry at absolute zero

Heazlewood¹,

Softley

2021

Nat Rev Chem

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The prospect of cooling matter down to temperatures that are close to the absolute zero raises intriguing questions about how chemical reactivity changes under these extreme conditions. Although some types of chemical reaction still occur at 1 µK, they can no longer adhere to the conventional picture of reactants passing over an activation energy barrier to become products. Indeed at ultracold temperatures, the system enters a fully quantum regime, and quantum mechanics replaces the classical picture of colliding particles. In this Review, we discuss recent experimental and theoretical developments that allow us to explore chemical reactions at temperatures that range from 10 K to 500 nK. Although the field is still in its infancy, exceptional control has already been demonstrated over reactivity at low temperatures.ultracold temperatures, the classical description of the collision of particles needs to be replaced with a quantum description and the picture of a ball rolling over a hill needs to be replaced by that of a wave propagating across a barrier.The quantum regime is a physical regime in which our basic understanding of how chemical processes happen, in terms of molecules bumping into each other and breaking and remaking bonds, needs to be challenged. Strictly speaking, the dynamical system of moving and colliding molecules needs to be described as a superposition of partial waves, the components of which represent the different angular momentum states associated with the relative motion of the colliding particles. As the temperature is lowered, the system moves towards a regime in which it can be described by just a few quantised collisional angular momentum states (and, ultimately, just a single state). We denote the collisions as 's-wave' or 'p-wave' collisions (known as the partial-wave description) to represent those with zero or one unit of collisional angular momentum, respectively. Furthermore, in the quantum regime the population of molecular quantum states is distributed over just a few rovibrational states and ultimately collapses to a single quantum state at the lowest temperatures (under conditions of thermal equilibrium). At low temperatures, quantum effects on the rate coefficient and other properties of the reaction, such as collision energy resonances, quantum reflection and geometric phase (described in detail in the 'Reactions in the ultracold regime' section), are most likely to be observable. This is in contrast to what we observe at room temperature, where we understand the overall rate of a process to be an average of the behaviours of individual collisions of molecules with vastly varying sets of quantum numbers and a distribution of energies.When the temperature reaches sub-µK, the translational wavelength typically exceeds the average separation of molecules in the sample, even for a low density gas, and ultimately the system may enter the regime of quantum degeneracy (for example, bosonic particles that form a Bose-Einstein condensate, in which all particles are in the same quan...

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“…The radiative lifetime of the Ca quantum state was reported to dictate the reaction dynamics at the lowest collision energies, in contrast to capture theory predictions, resulting in a suppression of the reactivity of Ca atoms in short-lived excited states. 122 Hybrid traps have also identified striking differences in the reaction dynamics of charge transfer collisions in Rb + N + 2 and Rb + O + 2 -systems where one might intuitively expect to see comparable behaviour. With the assistance of classical-capture, quasiclassical-trajectory and quantum-scattering calculations, the delicate interaction between short-range and long-range effects has been identified as the cause of the different charge transfer reaction mechanisms observed for the different reaction channels.…”

Section: Ion-neutral Reactionsmentioning

confidence: 99%