Photodissociation and reaction dynamics
This themed issue includes a collection of articles on photodissociation and reaction dynamics and marks the occasion of Professor Mike Ashfold's 65th birthday.
Photoinduced C–H bond fission in prototypical organic molecules and radicals
We survey and assess current knowledge regarding the primary photochemistry of hydrocarbon molecules and radicals.
Probing ultrafast dynamics during and after passing through conical intersections
Time-resolved photoelectron spectroscopy using vacuum-UV probe pulses enables observing ultrafast dynamics during and after passing through conical intersections.
Energetics and ionization dynamics of two diarylketone molecules: benzophenone and fluorenone
This paper reports on the single photon ionization of benzophenone and fluorenone and the subsequent complex dynamics fragmentation of the benzophenone cation. It shows pre-ionizing fragmentation in the case of benzophenone.
Energy- and conformer-dependent excited-state relaxation of an E/Z photoswitchable thienyl-ethene
Ultrafast spectroscopy reveals how conformers and complex photophysical relaxation cascades determine the cis-to-trans photoswitching efficiency of bis(bithienyl)-dicyanoethene (4TCE).
Field modified spin–orbit potential curves of IBr. Preliminary dynamical results
We revisit the seminal work on the control of IBr photodissociation using a strong non-resonant IR pulse, calculating the full 36-state manifold of spin–orbit coupled states. Preliminary results on the eld-driven IBr dissociation dynamics are presented.
New insights into the dissociation dynamics of methylated anilines
Combined time-resolved photoelectron spectroscopy and photofragment imaging supports a possible valence-to-Rydberg decay mechanism in methylated anilines.
Exploring ultraviolet photoinduced charge-transfer dynamics in a model dinucleotide of guanine and thymine
We unequivocally demonstrate that the Franck–Condon excited states of 2′-deoxyguanosine 3′-monophospate 5′-thymidine are significantly delocalised across both nucleobases, and mediate ultrafast exciplex product formation.
Competition between folded and extended structures of alanylalanine (Ala-Ala) in a molecular beam
Structural analysis of the neutral dipeptide Ala-Ala by action spectroscopy using IRMPD-VUV spectroscopy reveals predominance of extended structure.
Mode-specific excited-state dynamics of N-methylpyrrole
A picosecond time-resolved dynamics study unravels the photo-physical properties of N-methylpyrrole in excited-states in a mode-specific way.
Exploring Norrish type I and type II reactions: an ab initio mechanistic study highlighting singlet-state mediated chemistry
Norrish reactions are important photo-induced reactions in mainstream organic chemistry and are implicated in many industrially and biologically relevant processes and in the processing of carbonyl molecules in the atmosphere.
Ultrafast electronic relaxations from the S3 state of pyrene
The ultrafast relaxation occurring in pyrene upon excitation at 4.68 eV was studied in a supersonic gas-jet fs pump–probe experiment.
The role of symmetric functionalisation on photoisomerisation of a UV commercial chemical filter
Photoisomerisation has been shown to be an efficient excited-state relaxation mechanism for a variety of nature-based and artificial-based molecular systems.
The effect of CO rotation from shaped pulse polarization on reactions that form C2
The effect of CO rotational energy on bimolecular reactions to form electronically excited C2 is reported here.
Rotational dependence of the branching ratios and fragment angular distributions for the photodissociation of 12C16O in the Rydberg 4p(2) and 5p(0) complex region (92.84–93.37 nm)
Various patterns of rotational dependence for the photodissociation branching ratios and irregular angular distributions of the photofragments have been observed.
Ultrafast and radiationless electronic excited state decay of uracil and thymine cations: computing the effects of dynamic electron correlation
In this article we characterise the radiationless decay of the first few electronic excited states of the cations of DNA/RNA nucleobases uracil and thymine, including the effects of dynamic electron correlation on energies and geometries (optimised with XMS-CASPT2).
Understanding CO oxidation on the Pt(111) surface based on a reaction route network
Kinetic analysis by the rate constant matrix contraction on the reaction route network of CO oxidation on the Pt(111) surface obtained by the artificial force induced reaction reveals the impact of entropic contributions arising from a variety of local minima and transition states.
EVB and polarizable MM study of energy relaxation in fluorine–acetonitrile reactions
Many-body effects can impact on rates of energy transfer from a ‘hot’ DF solute to acetonitrile solvent.
Catalytic dissociation of tris(dimethylamino)silane on hot tungsten and tantalum filament surfaces
Tris(dimethylamino)silane catalytically dissociates on W and Ta surfaces to form ˙CH3 and H3C–NCH2, favored at low and high temperatures, respectively.
Unraveling structural dynamics in isoenergetic excited S1 and multi-excitonic 1(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy
Ultrafast Raman loss spectroscopy provides a direct evidence for the structural changes that occur during the evolution from the S1 to the 1(TT) state of BPEA in solution.
A study of the reactions of Al+ ions with O3, N2, O2, CO2 and H2O: influence on Al+ chemistry in planetary ionospheres
First measurements of Al+ ion reaction kinetics relevant to meteor-ablated metal chemistry in planetary upper atmospheres.
Mapping the intrinsic absorption properties and photodegradation pathways of the protonated and deprotonated forms of the sunscreen oxybenzone
Laser photodissociation experiments on gas-phase protonated and deprotonated oxybenzone reveal how the absorption properties and photodegradation products are significantly affected by pH.
Time-resolved imaging of bound and dissociating nuclear wave packets in strong-field ionized iodomethane
We report the results of a time-resolved coincident ion momentum imaging experiment probing nuclear wave packet dynamics in the strong-field ionization and dissociation of iodomethane (CH3I).
Energy and orientation independence of the channel branching in Ne* + ND3 chemi-ionisation
Collisions between metastable neon and ammonia result in either dissociative or Penning ionisation. Neither process exhibits a steric effect.
Photoinduced electron-driven proton transfer from water to an N-heterocyclic chromophore: nonadiabatic dynamics studies for pyridine–water clusters
We performed the excited-state dynamics simulations for pyridine–water clusters and found the more water molecules involved in the cluster, the higher efficiency the water-splitting reaction has, which is qualitatively in consistent with a recent gas-phase experimental observations.
Direct observation of product-pair correlations in rotationally inelastic collisions of ND3 with D2
Rotational product-pair correlations have been observed, while ND3 was rotationally excited, D2 was simultaneously rotationally excited and de-excited.
Experimental and computational studies of Criegee intermediate reactions with NH3 and CH3NH2
The significance of removal of atmospheric ammonia and amines by reaction with Criegee intermediates is assessed by kinetic studies.
Anharmonic excited state frequencies of para-difluorobenzene, toluene and catechol using analytic RI-CC2 second derivatives
Analytic second nuclear derivatives for excited electronic state energies have been implemented for RI-CC2, CIS(D) and ADC(2) models and used in VPT2 calculations of excited state frequencies.
C–I and C–F bond-breaking dynamics in the dissociative electron ionization of CF3I
We present a comprehensive experimental study into the dissociative electron ionization dynamics of CF3I at energies ranging from 20 to 100 eV.
Photoionization and dissociative photoionization of propynal in the gas phase: theory and experiment
Propynal (HCCCHO) is a compound of considerable astrochemical interest and observed in several interstellar objects.
DEA dynamics of chlorine dioxide probed by velocity slice imaging
The dissociative electron attachment dynamics of atmospherically important chlorine dioxide (OClO) is unravelled for the first time using velocity slice imaging.
How reactant polarization can be used to change the effect of interference on reactive collisions
Changes in the reactants' polarization have a strong effect on the shape of the differential cross sections when they are governed by interferences between two or more mechanisms.
Isotope-selective chemistry in the Be+(2S1/2) + HOD → BeOD+/BeOH+ + H/D reaction
Low temperature reactions between laser-cooled Be+(2S1/2) ions and partially deuterated water (HOD) molecules have been investigated using an ion trap and interpreted with zero-point corrected quasi-classical trajectory calculations on a highly accurate global potential energy surface for the ground electronic state.
Dynamics and quantum yields of H2 + CH2CO as a primary photolysis channel in CH3CHO
A new ketene + H2 channel in CH3CHO photolysis is not modelled by quasi-classical trajectories over the transition state.
Photofragment spin-polarization measurements via magnetization quantum beats: dynamics of DI photodissociation
We report the electron-spin polarization of D atoms from the photodissociation of DI, at 213 nm and 266 nm, by measuring the magnetization quantum beats of the D atoms with a pick-up coil.
Dynamics of benzene excimer formation from the parallel-displaced dimer
Charge transfer, exciton localization and time scales in benzene excimer formation after a S0–S1 transition from the parallel-displaced structure were characterized by surface-hopping dynamics.
Detection of the O2 A′3ΔU Herzberg III state by photofragment imaging
Photofragment imaging provides a sensitive method for detection of the O2 A′3Δu Herzberg III state using a one-laser dissociation/ionization scheme combined with velocity map imaging of atomic oxygen photofragments.
Fast beam photofragment translational spectroscopy of the phenoxy radical at 225 nm, 290 nm, and 533 nm
Photodissociation experiments are used to study two- and three-body fragmentation by collecting fragments in coincidence.
UV photofragmentation dynamics of acetaldehyde cations prepared by single-photon VUV ionization
UV excitation of cold acetaldehyde cations prepared by single-photon VUV ionization results in remarkably rich photochemistry.
Solvent reorganization triggers photo-induced solvated electron generation in phenol
Charge-transfer states with large electron–hole separation, correlating to the formation of solvated electrons, are found below the maximum of the absorbing ππ* band of solvated phenol.
Mechanisms of photoreactivity in hydrogen-bonded adenine–H2O complexes
The mechanisms of photoinduced reactions of adenine with water molecules in hydrogen-bonded adenine–water complexes were investigated with ab initio wave-function-based electronic-structure calculations.
Dynamics of the photodissociation of ethyl iodide from the origin of the B band. A slice imaging study
The electronic predissociation dynamics and stereodynamics of ethyl iodide from the origin of the B-band are studied by slice imaging and ab initio calculations.
Photoelectron spectroscopic study of I−·ICF3: a frontside attack SN2 pre-reaction complex
The I−·ICF3 complex, a frontside attack pre-reaction complex of a classic SN2 reaction, is produced and studied using photoelectron spectroscopy.
Automatic and semi-automatic assignment and fitting of spectra with PGOPHER
Nearest lines plot, making assignment of dense and complex spectra easy.
Correspondence between electronic structure calculations and simulations: nonadiabatic dynamics in CS2
The choice of ab initio electronic structure method is an important factor in determining the fidelity of nonadiabatic dynamics simulations.
Vibrational predissociation of the phenol–water dimer: a view from the water
Predissociation dynamics of the phenol–water dimer were studied by detecting H2O fragments and using VMI to infer internal state distributions.
Photon catalysis of deuterium iodide photodissociation
The photodissociation of deuterium iodide is catalyzed by the electric field supplied by nonresonant IR photons.
Proton transfer from pinene stabilizes water clusters
Molecular beams experiments and ab initio theory reveal indirect formation of protonated water clusters by ionization of pinene.
Representation of coupled adiabatic potential energy surfaces using neural network based quasi-diabatic Hamiltonians: 1,2 2A′ states of LiFH
A general algorithm for determining diabatic representations from adiabatic energies, energy gradients and derivative couplings using neural networks is introduced.
Imaging H abstraction dynamics in crossed molecular beams: O(3P) + propanol isomers
Direct rebound dynamics are revealed for bimolecular reaction of the ground state O(3P) atom with propanol isomers, involving the post transition state long-range dipole–dipole interaction between the dipolar OH and hydroxypropyl radicals.
Structural isomers and low-lying electronic states of gas-phase M+(N2O)n (M = Co, Rh, Ir) ion–molecule complexes
The structures of gas-phase group nine cation–nitrous oxide metal–ligand complexes, M+(N2O)n (M = Co, Rh, Ir; n = 2–7) have been determined by a combination of infrared photodissociation spectroscopy and density functional theory.
Differential steric effects in the inelastic scattering of NO(X) + Ar: spin–orbit changing transitions
The differential steric effect for spin–orbit changing collisions of NO with Ar is determined for the first time.
Dimers of acetic acid in helium nanodroplets
Two metastable dimers are created inside superfluid helium and studied using infrared spectroscopy to provide insight into condensed phase structures.
Two-dimensional electronic-vibrational spectroscopic study of conical intersection dynamics: an experimental and electronic structure study
The relaxation from the lowest singlet excited state of the triphenylmethane dyes, crystal violet and malachite green, is studied via two-dimensional electronic-vibrational (2DEV) spectroscopy.
Vectorial imaging of the photodissociation of 2-bromobutane oriented via hexapolar state selection
Molecular orientation techniques are becoming available in the study of elementary chemical processes, in order to highlight those structural and dynamical properties that would be concealed by random rotational motions.
Finite-temperature Wigner phase-space sampling and temperature effects on the excited-state dynamics of 2-nitronaphthalene
The concept of finite temperature Wigner phase-space sampling allowing the population of vibrationally excited states is introduced and employed to study temperature effects on the absorption spectrum of 2-nitronaphtalene (2NN) and its relaxation dynamics.
Photodissociation of CH2BrI using cavity ring-down spectroscopy: in search of a BrI elimination channel
Photodissociation of CH2BrI was investigated in search of unimolecular elimination of BrI via a primary channel using cavity ring-down absorption spectroscopy (CRDS) at 248 nm.
Imaging pair-correlated reaction cross sections in F + CH3D(νb = 0, 1) → CH2D(ν4 = 1) + HF(ν)
Product pair-correlated distributions in the title reactions are revealed by imaging the state-tagged CH2D(ν4 = 1) products.
Effects of symmetry, methyl groups and serendipity on intramolecular vibrational energy dispersal
Intramolecular vibrational dispersal of vibrational energy is more efficient in the symmetrically-substituted p-xylene molecule than in p-fluorotoluene, p-chlorofluorobenzene or p-difluorobenzene.
On the formation and the isomer specific detection of methylacetylene (CH3CCH), propene (CH3CHCH2), cyclopropane (c-C3H6), vinylacetylene (CH2CHCCH), and 1,3-butadiene (CH2CHCHCH2) from interstellar methane ice analogues
The isomer specific detection of complex hydrocarbons from irradiated methane ice plus their yields and formation routes have been elucidated.
About this collection
Guest-edited by Andrew Orr-Ewing (University of Bristol), this themed issue highlights the latest research in the fundamental mechanisms of photochemical and chemical reactions in the gas and liquid phases, featuring both experimental and theoretical studies.