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Out of plane bending potential with zero point energy levels and probability distributions for H and Mu and variation of a-a(0) Gauss × 10 4 .
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Zero-point vibrational level averaging for electron spin resonance (ESR) and muon spin resonance (µSR) hyperfine coupling constants (HFCCs) are computed for H and Mu isotopomers of the cyclohexadienyl radical. A local mode approximation previously developed for computation of the effect of replacement of H by D on 13C-NMR chemical shifts is used. D...
Citations
... shell correlated methods. It is found that several of these methods provide reasonable overall agreement with experiment [8]. : The plot at left shows the degree of agreement of observed and computed 13C chemical shifts using DFT methods for all carbons of the above compounds that correspond to separation greater than one carbon, i.e. the chemical shift for the direct substitution is not included. ...
... In the above expression, BO separated coordinates are collectively represented as R BOS . The exact multicomponent Hamiltonian be written as the sum of two operators H exact (r I , r II , R BOS ) = H(r I , r II ; R BOS ) + T R BOS (2) where, T R BOS is the kinetic energy operators associated with the BO separated coordinates. The general form of the Hamiltonian for the multicomponent system is defined as H(r I , r II ; R BOS ) = H I (r I ; R BOS ) + H II (r II ; R BOS ) +V I,II (r I , r II ) ...
Multicomponent systems are defined as chemical systems that require a quantum
mechanical description of two or more different types of particles.
Non-Born-Oppenheimer electron-nuclear interactions in molecules, electron-hole
interactions in electronically excited nanoparticles, and electron-positron
interactions are examples of physical systems that require a multicomponent
quantum mechanical formalism. The central challenge in the theoretical
treatment of multicomponent systems is capturing the many-body correlation
effects that exist not only between particles of identical types
(electron-electron) but also between particles of different types
(electron-nuclear and electron-hole). In this work, the development and
implementation of multicomponent coupled-cluster (mcCC) theory for treating
particle-particle correlation in multicomponent systems is presented. This
method provides a balanced treatment of many-particle correlation in a general
multicomponent system while maintaining a size-consistent and size-extensive
formalism. The coupled-cluster ansatz presented here is the extension of the
electronic structure CCSD formulation for multicomponent systems and is defined
as $\vert \Psi_\mathrm{mcCC} \rangle =
e^{T_1^\mathrm{I}+T_2^\mathrm{I}+T_1^\mathrm{II}+T_2^\mathrm{II}+T_{11}^\mathrm{I,II}+T_{12}^\mathrm{I,II}+T_{21}^\mathrm{I,II}+T_{22}^\mathrm{I,II}}\vert
0^\mathrm{I}0^\mathrm{II}\rangle$. The applicability of the mcCC method was
demonstrated by computing biexciton binding energies for multiexcitonic systems
and benchmarking the results against full configuration interaction
calculations. The results demonstrated that connected cluster operators that
generate simultaneous excitation in type I and type II space are critical for
capturing electron-hole correlation in multiexcitonic systems.
... Attempts have also been made to better model the contributions of ZPE shift in theoretical calculations, using ex. local mode approximations [17]. ...
Spin polarized positive muons injected in matter serve as magnetic probes for the investigation of physical and chemical properties of free radicals, mechanisms of free radical reactions and their formations, and radiation effects. All muon techniques rely on the evolution of spin polarization (of the muon) and in that respect are similar to conventional magnetic resonance techniques. The applications of the muon as a hyperfine probe in several fields in chemistry are described.
Muonium is a combination of first- and second-generation matter formed by the electrostatic interaction between an electron and an antimuon (μ+). Although a well-known physical system, their ability to form collective excitations in molecules had not been observed. Here, we give evidence for the detection of a muonium state that propagates in a molecular semiconductor lattice via thermally activated dynamics: a muonium polaron. By measuring the temperature dependence of the depolarization of the muonium state in C60, we observe a thermal narrowing of the hyperfine distribution that we attribute to the dynamics of the muonium between molecular sites. As a result of the time scale for muonium decay, the energies involved, charge and spin selectivity, this quasiparticle is a widely applicable experimental tool. It is an excellent probe of emerging electronic, dynamic, and magnetic states at interfaces and in low dimensional systems, where direct spatial probing is an experimental challenge owing to the buried interface, nanoscale elements providing the functionality localization and small magnitude of the effects.
The use of implanted muons to probe the spin dynamics and electronic excitations in organic materials is reviewed. At first, a brief introduction to the historical context and background of the muon technique is given, followed by an outline of some of the underlying theoretical models needed to quantitatively interpret data taken on organic molecules. Caution is advised when using certain theoretical models for the interpretation of low-field spin relaxation data. The next section deals with spin dynamics in soft materials, and starts with discussing many of the key results in thin films, followed by a review of bulk measurements in three different materials classes - polymers, biologically active molecules, and small molecules. Finally, we present a detailed discussion of the density functional theory methodology when applied to μSR, and present the common issues encountered when trying to perform these calculations to support muon experiments. In particular, we discuss a method for benchmarking to manage the approximations inherent to the technique and common sources of errors that can sometimes fortuitously cancel.
Previous electronic structure studies have revealed that the glycine-K+ complex has a low-barrier intramolecular proton-transfer pathway between zwitterionic and neutral forms. We have theoretically calculated quantum molecular structures of this complex including the proton-transfer process using a path-integral molecular dynamics technique on an interpolated potential energy surface developed at the B3LYP level of theory. When the transferring proton is substituted by muon, it was found that the muonium atom showed a broad distribution around the proton(muon)-transfer transition state region between the neutral and zwitterionic structures due to extreme nuclear quantum effects of a very light particle although the distribution peak is slightly deviated from the transition state. The present study demonstrates that Mu can be employed to probe transition-state regions of potential energy surfaces of proton-transfer chemical reactions.
The muon hyperfine coupling constant (Aμ) of the muoniated cyclohexadienyl radical (C6H6Mu) has been directly measured in a 5 mM solution of benzene in water by the radio-frequency muon spin resonance (RF-μSR) technique. The relative shift of Aμ in aqueous solution compared with the value in neat benzene (ΔAμ/Aμ = +0.98(5)% at 293 K) can now be compared directly with theoretical predictions. Application of the RF-μSR method to other dilute systems will provide extremely important information on understanding solvent effects.
