Chemistry With Controlled Ions

Willitsch, Stefan

doi:10.1002/9781119324560.ch5

Cited by 44 publications

(61 citation statements)

References 151 publications

(229 reference statements)

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“…We envision experiments in which, e.g., the state of a single molecule and its chemical identity is monitored during collisions or reactions. This type of state-tostate chemistry experiments can shed light on inelastic and reactive processes on the single-molecule level 36,41,42 in a fashion similar to recent work investigating spinconserving and non-conserving collisions in ultracold atom-ion reactions [43][44][45][46] .…”

Section: Introductionmentioning

confidence: 79%

State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions

et al. 2019

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We present theoretical and experimental progress towards a new approach for the precision spectroscopy, coherent manipulation and state-to-state chemistry of single isolated molecular ions in the gas phase. Our method consists of a molecular beam for creating packets of rotationally cold neutrals from which a single molecule is state-selectively ionized and trapped inside a radiofrequency ion trap. In addition to the molecular ion, a single co-trapped atomic ion is used to cool the molecular external degrees of freedom to the ground state of the trap and to detect the molecular state using state-selective coherent motional excitation from a modulated optical-dipole force acting on the molecule. We present a detailed discussion and theoretical characterization of the present approach. We simulate the molecular signal experimentally using a single atomic ion indicating that different rovibronic molecular states can be resolved and individually detected with our method. The present approach for the coherent control and non-destructive detection of the quantum state of a single molecular ion opens up new perspectives for precision spectroscopies relevant for, e.g., tests of fundamental physical theories and the development of new types of clocks based on molecular vibrational transitions. It will also enable the observation and control of chemical reactions of single particles on the quantum level. While focusing on N + 2 as a prototypical example in the present work, our method is applicable to a wide range of diatomic and polyatomic molecules.

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Section: Introductionmentioning

confidence: 79%

State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions

et al. 2019

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“…30,31 From an experimental perspective, the most precise data on reaction mechanisms and dynamics can be gained from gas-phase studies performed under single-collision conditions. As the progress in molecular-beam experiments allows the probing of ever-larger systems under precisely defined conditions, 32,33 the open questions pertaining to the mechanistic details of Diels-Alder reactions become an attractive target of study. Since only scarce information is available on these important mechanistic aspects, 34 we present here a molecular dynamics study of the Diels-Alder reaction between 2,3-dibromo-1,3-butadiene (DBB) and maleic anhydride (MA) (see Scheme 1) which may serve as a guide for future experiments.…”

Section: Introductionmentioning

confidence: 99%

“…We have chosen DBB because it is a generic diene which fulfills the experimental requirements for conformational separation of its isomers by electrostatic deflection of a molecular beam, 32,33 thus enabling the characterization of conformational aspects and specificities of the reaction. MA is a widely used, activated dienophile which due to its symmetry simplifies the possible products of the reaction.…”

Section: Introductionmentioning

confidence: 99%

Reactive atomistic simulations of Diels-Alder reactions: The importance of molecular rotations

Rivero

Unke

Meuwly

et al. 2019

The Journal of Chemical Physics

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The Diels-Alder reaction between 2,3-dibromo-1,3-butadiene and maleic anhydride has been studied by means of multisurface adiabatic reactive molecular dynamics and the PhysNet neural network architecture. This system is used as a prototype to explore the concertedness, synchronicity and possible ways of promotion of Diels-Alder reactions. Analysis of the minimum dynamic path indicates that rotational energy is crucial (∼ 65%) to drive the system towards the transition state in addition to collision energy (∼ 20 %). Comparison with the reaction of butadiene and maleic anhydride shows that the presence of bromine substituents in the diene accentuates the importance of rotational excitation to promote the reaction. At the high total energies at which reactive events are recorded, the reaction is found to be direct and mostly synchronous. a) m.meuwly@unibas.ch b) stefan.willitsch@unibas.ch

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“…To simplify the problem, it is assumed that collisions are classical, short range, and instantaneous such that the ion's trajectory is defined at all times by Eq. (7). The trajectory after the collision must therefore have the same general form as Eq.…”

Section: B Ion-neutral Collisionsmentioning

confidence: 99%

Energy distributions of an ion in a radio-frequency trap immersed in a buffer gas under the influence of additional external forces

Rouse

Willitsch

2018

Phys. Rev. A

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An ion held in a radiofrequency trap interacting with a uniform buffer gas of neutral atoms develops a steady-state energy distribution characterised by a power-law tail at high energies instead of the exponential decay characteristic of thermal equilibrium. We have previously shown that the Tsallis statistics frequently used as an empirical model for this distribution is a good approximation when the ion is heated due to a combination of micromotion interruption and exchange of kinetic energy with the buffer gas [I. Rouse and S. Willitsch, Phys. Rev. Lett. 118, 143401 (2017)]. Here, we extend our treatment to include the heating due to additional motion of the ion caused by external forces, including the "excess micromotion" induced by uniform electric fields and rf phase offsets. We show that this also leads to a Tsallis distribution with a potentially different power-law exponent from that observed in the absence of this additional forced motion, with the difference increasing as the ratio of the mass of the neutral atoms to that of the ion decreases. Our results indicate that unless the excess micromotion is minimised to a very high degree, then even a system with very light neutrals and a heavy ion does not exhibit a thermal distribution.

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Chemistry With Controlled Ions

Cited by 44 publications

References 151 publications

State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions

State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions

Reactive atomistic simulations of Diels-Alder reactions: The importance of molecular rotations

Energy distributions of an ion in a radio-frequency trap immersed in a buffer gas under the influence of additional external forces

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