Dynamics of gas phase Ne* + NH3 and Ne* + ND3 Penning ionisation at low temperatures

Jankunas, Justin; Bertsche, Benjamin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

doi:10.1063/1.4883517

Cited by 86 publications

(164 citation statements)

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“…In particular, the approach by Jachymski et al, based on multichannel quantum-defect theory (MQDT), provides analytical expressions which can be easily compared with experimental data [9,14,15]. The model has been recently applied to a variety of systems [9,16,17]. In particular, for the Penning ionization of Ar by He( 3 S) [5], the rate coefficients have been fitted in a wide range of collision energies using only two parameters [9].…”

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confidence: 99%

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

et al. 2015

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We have calculated accurate quantum reactive and elastic cross sections for the prototypical barrierless reaction D + + H 2 (v = 0, j = 0) using a modified hyperspherical scattering method. The considered kinetic energy ranges from the ultracold to the Langevin regimes. A reaction rate coefficient practically constant in no less than eight orders of magnitude is obtained. The availability of accurate results for this system allows one to test the quantum theory by Jachymski et al. [K. Jachymski, M. Krych, P. S. Julienne, and Z. Idziaszek, Phys. Rev. Lett. 110, 213202 (2013)] in a nonuniversal case. The short-range reaction probability is rationalized using statistical model assumptions and related to a statistical factor. This provides a means to estimate one of the parameters that characterizes ultracold processes from first principles. The increasing availability of cold and ultracold samples of atoms and molecules has sprung great interest in chemical reactions at very low temperatures [1][2][3][4][5]. Although new experimental approaches [5] appear highly promising, advances in the field are hampered by technical problems in producing most molecules at low temperatures and high enough densities. In contrast to neutral species, ions can be easily trapped and cooled. The technology of Coulomb crystals in radiofrequency ion traps [6] and the possibility of combining them with traps for neutrals or with slow molecular beams [7,8] promise great progress in the analysis of ion-neutral reactions in the near future.Theoretical simulations employing standard ab initio approaches are not feasible for most of the systems thus far considered. For heavy systems (more convenient experimentally) there are no potential energy surfaces (PESs) accurate enough to describe processes near thresholds. Additionally, most of exact dynamical treatments face insurmountable problems in such regimes. However, in contrast to short-range (SR) chemical interactions, those occurring at long range (LR) can be more easily calculated. Moreover, theoretical approaches based only on the knowledge of the LR part of the PES have been able to describe recent experimental findings nearly quantitatively [1,9]. Indeed, processes at very low collision energies favor LR interactions, leading to the idea of universality in extreme cases [10]: the result of the collision depends exclusively on the LR behavior and not on the details of the PES. In this regard, recently proposed LR parametrization procedures [9,[11][12][13] Fitting experimental data, these models are able to predict nonmeasured values providing some insight into the underlying interactions. In particular, the approach by Jachymski et al., based on multichannel quantum-defect theory (MQDT), provides analytical expressions which can be easily compared with experimental data [9,14,15]. The model has been recently applied to a variety of systems [9,16,17]. In particular, for the Penning ionization of Ar by He( 3 S) [5], the rate coefficients have been fitted in a wide range of collision ener...

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confidence: 99%

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

et al. 2015

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“…To this end, we make use of the description based on quantum defect theory (QDT), which has been successfully applied before to describe Penning ionization of the NH 3 molecule. 19,20 The model relies on the knowledge of the interaction potential at long range and an effective parametrization of the short-range dynamics (see Refs. 19 and 28 for details).…”

Section: Theoretical Modelmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] In recent years, detailed investigation of scattering processes has attracted considerable interest in particular in the context of cold molecule formation and trapping. 9,10 Recent experimental developments have opened the route to investigations of molecular scattering in supersonic expansions at collision energies substantially below 10 K. 5,[11][12][13][14][15][16][17][18][19][20][21] The collision energy depends on the relative velocity of the reactants. In a molecular beams experiment this is determined not just by individual beam speeds but also by the angle between them.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies in a) andreas.osterwalder@epfl.ch the past years have demonstrated the power of this approach, addressing different aspects of Penning ionization reactions in collisions of excited rare gas atoms with other atoms, diatomics, or light polyatomic molecules. [13][14][15][17][18][19][20][21] Only a handful of low-energy collision studies of polyatomic molecules have been performed to date. [18][19][20][21] In general, higher mass and increasingly complex internal structure of the colliding molecules open more inelastic and reactive channels.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15][17][18][19][20][21] Only a handful of low-energy collision studies of polyatomic molecules have been performed to date. [18][19][20][21] In general, higher mass and increasingly complex internal structure of the colliding molecules open more inelastic and reactive channels. Therefore, the complete description of a cold chemical reaction must account for all possible reaction routes and also include inelastic collisions.…”

Section: Introductionmentioning

confidence: 99%

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Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3

Jankunas

Jachymski

Hapka

et al. 2016

The Journal of Chemical Physics

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Low energy reaction dynamics can strongly depend on the internal structure of the reactants. The role of rotationally inelastic processes in cold collisions involving polyatomic molecules has not been explored so far. Here we address this problem by performing a merged-beam study of the He( 3 S 1 )+CHF 3 Penning ionization reaction in a range of collision energies E/k B = 0.5-120 K. The experimental cross sections are compared with total reaction cross sections calculated within the framework of quantum defect theory. We find that the broad range of collision energies combined with the relatively small rotational constants of CHF 3 makes rotationally inelastic collisions a crucial player in the total reaction dynamics. Quantitative agreement between theory and experiment is only obtained if the energy-dependent probability for rotational excitation is included in the calculations, in stark contrast to previous experiments where classical scaling laws were able to describe the results. Published by AIP Publishing. [http://dx

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Stereoselectivity in Autoionization Reactions of Hydrogenated Molecules by Metastable Noble Gas Atoms: The Role of Electronic Couplings

Falcinelli

Rosi

Cavalli

et al. 2016

Chemistry A European J

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Focus in the present paper is on the analysis of total and partial ionization cross sections, measured in absolute value as a function of the collision energy, representative of the probability of ionic product formation in selected electronic states in Ne*-H2 O, H2 S, and NH3 collisions. In order to characterize the imaginary part of the optical potential, related to electronic couplings, we generalize a methodology to obtain direct information on the opacity function of these reactions. Such a methodology has been recently exploited to test the real part of the optical potential (S. Falcinelli et al., Chem. Eur. J., 2016, 22, 764-771). Depending on the balance of noncovalent contributions, the real part controls the approach of neutral reactants, the removal of ionic products, and the structure of the transition state. Strength, range, and stereoselectivity of electronic couplings, triggering these and many other reactions, are directly obtained from the present investigation.

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Dynamics of gas phase Ne* + NH3 and Ne* + ND3 Penning ionisation at low temperatures

Cited by 86 publications

References 57 publications

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3

Stereoselectivity in Autoionization Reactions of Hydrogenated Molecules by Metastable Noble Gas Atoms: The Role of Electronic Couplings

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