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Themed collection Quantum effects in small molecular systems

25 items
Open Access Paper

Heavy Rydberg states: large amplitude vibrations

New theory and calculations of extremely large vibrational amplitude states with heavy Rydberg character are reported in the H2 molecule.

Graphical abstract: Heavy Rydberg states: large amplitude vibrations
From the themed collection: Quantum effects in small molecular systems
Paper

The influence of aqueous solvent on the electronic structure and non-adiabatic dynamics of indole explored by liquid-jet photoelectron spectroscopy

Time-resolved photoelectron spectroscopy (TRPES) in a liquid micro-jet is implemented here to investigate the influence of water on the electronic structure and dynamics of indole, the chromophore of the amino acid tryptophan.

Graphical abstract: The influence of aqueous solvent on the electronic structure and non-adiabatic dynamics of indole explored by liquid-jet photoelectron spectroscopy
From the themed collection: Quantum effects in small molecular systems
Paper

Spectral signatures of proton delocalization in H+(H2O)n=1−4 ions

Vibrational couplings in protonated water clusters are described by harmonic analysis, vibrational perturbation theory (VPT2) and diffusion Monte Carlo (DMC) approaches.

Graphical abstract: Spectral signatures of proton delocalization in H+(H2O)n=1−4 ions
From the themed collection: Quantum effects in small molecular systems
Paper

Fully quantum calculation of the second and third virial coefficients of water and its isotopologues from ab initio potentials

Path-Integral Monte Carlo methods were applied to calculate the second, B(T), and the third, C(T), virial coefficients for water and heavy water from state-of-art flexible potentials.

Graphical abstract: Fully quantum calculation of the second and third virial coefficients of water and its isotopologues from ab initio potentials
From the themed collection: Quantum effects in small molecular systems
Paper

Spiers Memorial Lecture

This Spiers Memorial Lecture discusses quantum effects that can be calculated and observed in the chemical reactions of small molecules.

Graphical abstract: Spiers Memorial Lecture Introductory lecture: quantum dynamics of chemical reactions
From the themed collection: Quantum effects in small molecular systems
Paper

On the importance of initial conditions for excited-state dynamics

The vast majority of ab initio excited-state simulations are performed within semiclassical, trajectory-based approaches. Apart from the underlying electronic-structure theory, the reliability of the simulations is controlled by a selection of initial conditions for the classical trajectories. We discuss appropriate choices of initial conditions for simulations of different experimental arrangements: dynamics initiated by continuum-wave (CW) laser fields or triggered by ultrashort laser pulses.

Graphical abstract: On the importance of initial conditions for excited-state dynamics
From the themed collection: Quantum effects in small molecular systems
Paper

Teaching vibrational spectra to assign themselves

A new paradigm is described for assigning vibrational spectra that follows the blue path rather than the red one.

Graphical abstract: Teaching vibrational spectra to assign themselves
From the themed collection: Quantum effects in small molecular systems
Paper

Theoretical studies of atmospheric molecular complexes interacting with NIR to UV light

Theoretical structural and spectroscopic data for weakly bonded atmospheric complexes of formaldehyde interacting with Earth’s electromagnetic spectrum.

Graphical abstract: Theoretical studies of atmospheric molecular complexes interacting with NIR to UV light
From the themed collection: Quantum effects in small molecular systems
Paper

Quantum and classical IR spectra of (HCOOH)2, (DCOOH)2 and (DCOOD)2 using ab initio potential energy and dipole moment surfaces

Full-dimensional (24 modes) quantum calculation of the IR spectrum of (DCOOD)2, and comparison with classical MD one.

Graphical abstract: Quantum and classical IR spectra of (HCOOH)2, (DCOOH)2 and (DCOOD)2 using ab initio potential energy and dipole moment surfaces
From the themed collection: Quantum effects in small molecular systems
Paper

Alignment of 17O-enriched water–endofullerene H2O@C60 in a liquid crystal matrix

The water molecule in H2O@C60 endofullerene, dissolved in a nematic liquid crystal, is aligned with its plane perpendicular to the liquid crystal director.

Graphical abstract: Alignment of 17O-enriched water–endofullerene H2O@C60 in a liquid crystal matrix
From the themed collection: Quantum effects in small molecular systems
Paper

Does cage quantum delocalisation influence the translation–rotational bound states of molecular hydrogen in clathrate hydrate?

In this study, we examine the effect of a flexible description of the clathrate hydrate framework on the translation–rotation (TR) eigenstates of guest molecules such as molecular hydrogen.

Graphical abstract: Does cage quantum delocalisation influence the translation–rotational bound states of molecular hydrogen in clathrate hydrate?
From the themed collection: Quantum effects in small molecular systems
Open Access Paper

Curve crossing in a manifold of coupled electronic states: direct quantum dynamics simulations of formamide

Fully quantum direct dynamics simulations generate the potential surface manifold for the photo-excited dynamics of small organic molecules.

Graphical abstract: Curve crossing in a manifold of coupled electronic states: direct quantum dynamics simulations of formamide
From the themed collection: Quantum effects in small molecular systems
Paper

Excited state dynamics and time-resolved photoelectron spectroscopy of para-xylylene

We investigated the excited-state dynamics of para-xylylene using a combination of field-induced surface hopping simulations and time-resolved photoionisation experiments. Ultraviolet excitation is followed by nonadiabatic relaxation to the ground state in a two-step mechanism on the sub-ps time scale.

Graphical abstract: Excited state dynamics and time-resolved photoelectron spectroscopy of para-xylylene
From the themed collection: Quantum effects in small molecular systems
Paper

On the gas-phase formation of the HCO anion: accurate quantum study of the H + CO radiative association and HCO radiative electron attachment

Here, we present the first study of the radiative association of H and CO to form the HCO anion within a quantum time-independent approach..

Graphical abstract: On the gas-phase formation of the HCO− anion: accurate quantum study of the H− + CO radiative association and HCO radiative electron attachment
From the themed collection: Quantum effects in small molecular systems
Paper

Disentangling the complex spectrum of the ethynyl cation

We investigate the low-lying electronic states of the ethynyl cation, C2H+, using pure ab initio methodologies.

Graphical abstract: Disentangling the complex spectrum of the ethynyl cation
From the themed collection: Quantum effects in small molecular systems
Paper

Properties of Feshbach and “shape”-resonances in ozone and their role in recombination reactions and anomalous isotope effects

Three reaction pathways for formation of symmetric and asymmetric isotopologues of ozone.

Graphical abstract: Properties of Feshbach and “shape”-resonances in ozone and their role in recombination reactions and anomalous isotope effects
From the themed collection: Quantum effects in small molecular systems
Open Access Paper

Collisional relaxation kinetics for ortho and para NH2 under photodetachment in cold ion traps

Computational modeling and selective photodetachment experiments allow us to match the global temporal evolution of anions’ losses in a trap with the selective losses estimated from theory.

Graphical abstract: Collisional relaxation kinetics for ortho and para NH2− under photodetachment in cold ion traps
From the themed collection: Quantum effects in small molecular systems
Paper

Electron-driven proton transfer enables nonradiative photodeactivation in microhydrated 2-aminoimidazole

Prebiotically credible activator of non-enzymatic RNA template-copying, 2-aminoimidazole, is protected from destructive photochemistry by photoacidity.

Graphical abstract: Electron-driven proton transfer enables nonradiative photodeactivation in microhydrated 2-aminoimidazole
From the themed collection: Quantum effects in small molecular systems
Open Access Paper

Proton transfer in guanine–cytosine base pair analogues studied by NMR spectroscopy and PIMD simulations

NMR isotope shifts provide a unique possibility to study the nuclear quantum effects of hydrogen-bonded nucleobases.

Graphical abstract: Proton transfer in guanine–cytosine base pair analogues studied by NMR spectroscopy and PIMD simulations
From the themed collection: Quantum effects in small molecular systems
Paper

Stereochemistry-dependent hydrogen bonds stabilise stacked conformations in jet-cooled cyclic dipeptides: (LD) vs. (LL) cyclo tyrosine–tyrosine

Changing the chirality of one residue prevents the formation of an OH⋯O intramolecular hydrogen bond in cyclo di-tyrosine.

Graphical abstract: Stereochemistry-dependent hydrogen bonds stabilise stacked conformations in jet-cooled cyclic dipeptides: (LD) vs. (LL) cyclo tyrosine–tyrosine
From the themed collection: Quantum effects in small molecular systems
Open Access Paper

Ab initio instanton rate theory made efficient using Gaussian process regression

In this paper, we describe how we use Gaussian process regression to fit a local representation of the potential energy surface and thereby obtain the instanton rate using only a small number of ab initio calculations.

Graphical abstract: Ab initio instanton rate theory made efficient using Gaussian process regression
From the themed collection: Quantum effects in small molecular systems
Paper

Large amplitude motions within molecules trapped in solid parahydrogen

Large amplitude motions involving hydrogen tunnelling can be preserved in molecules trapped in parahydrogen matrices, and observed through band splitting or under certain conditions by a temporal evolution of the spectra.

Graphical abstract: Large amplitude motions within molecules trapped in solid parahydrogen
From the themed collection: Quantum effects in small molecular systems
Paper

Multiple pulse coherent dynamics and wave packet control of the N2 a′′ 1Σ+g dark state by attosecond four-wave mixing

Dark states of molecular nitrogen in the XUV region are spectroscopically investigated using few-femtosecond dynamic wave packet control.

Graphical abstract: Multiple pulse coherent dynamics and wave packet control of the N2 a′′ 1Σ+g dark state by attosecond four-wave mixing
From the themed collection: Quantum effects in small molecular systems
Paper

Effects of symmetry breaking on the translation–rotation eigenstates of H2, HF, and H2O inside the fullerene C60

Effects of symmetry breaking on the translation–rotation eigenstates of M@C60 (M = H2, HF, H2O) are visible in the infrared spectra of endofullerenes.

Graphical abstract: Effects of symmetry breaking on the translation–rotation eigenstates of H2, HF, and H2O inside the fullerene C60
From the themed collection: Quantum effects in small molecular systems
Paper

Natural reaction channels in H + CHD3 → H2 + CD3

Natural reaction channels control the mode-specific chemistry of methane and its isotopomeres.

Graphical abstract: Natural reaction channels in H + CHD3 → H2 + CD3
From the themed collection: Quantum effects in small molecular systems
25 items

About this collection

We are delighted to share with you a selection of the papers which will be presented at our Faraday Discussion on Quantum effects in small molecular systems taking place in Edinburgh, UK in September 2018. More information about the event may be found here: http://rsc.li/quantum-fd2018. Additional articles will be added to the collection as they are published. The final versions of all the articles presented and a record of the live discussions will be published after the event.

The quantum mechanical properties of small molecules provide the basis for our quantitative understanding of chemistry and a testing ground for new theories of molecular structure and reactivity. With modern methods, small molecular systems can be investigated in extraordinary detail by high-resolution spectroscopic techniques in the frequency or the time domains, and by complementary theoretical and computational advances. This combination of cutting-edge approaches provides rigorous tests of our understanding of quantum phenomena in chemistry. The chemical properties of small molecules continue to present rich challenges at the chemistry/physics interface since these molecules exhibit properties in isolation, and interact with their environments, in ways that are not yet fully understood. The coupled electronic and nuclear motions may lead to complex structural or dynamical features that can now be observed experimentally. From a theoretical point of view, these features can only be explained if the quantum nature of the atomic nuclei is considered together with the possible couplings between nuclear and electronic degrees of freedom.

New developments, from both the theoretical and experimental side, are urgently needed if the properties of small molecules are to be optimally exploited in future technological, engineering and biological applications of outstanding importance.

This Faraday Discussion will address the quantum dynamical properties of small molecules, both in isolation where extraordinarily detailed and precise measurements and calculations are now emerging, and when embedded in complex media such as molecular clusters, quantum fluids and bulk liquids.

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