Themed collection 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.

We survey and assess current knowledge regarding the primary photochemistry of hydrocarbon molecules and radicals.

Time-resolved photoelectron spectroscopy using vacuum-UV probe pulses enables observing ultrafast dynamics during and after passing through conical intersections.

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.

Ultrafast spectroscopy reveals how conformers and complex photophysical relaxation cascades determine the cis-to-trans photoswitching efficiency of bis(bithienyl)-dicyanoethene (4TCE).

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.

Combined time-resolved photoelectron spectroscopy and photofragment imaging supports a possible valence-to-Rydberg decay mechanism in methylated anilines.

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.

Structural analysis of the neutral dipeptide Ala-Ala by action spectroscopy using IRMPD-VUV spectroscopy reveals predominance of extended structure.

A picosecond time-resolved dynamics study unravels the photo-physical properties of N-methylpyrrole in excited-states in a mode-specific way.

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.

The ultrafast relaxation occurring in pyrene upon excitation at 4.68 eV was studied in a supersonic gas-jet fs pump–probe experiment.

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 rotational energy on bimolecular reactions to form electronically excited C₂ is reported here.

Various patterns of rotational dependence for the photodissociation branching ratios and irregular angular distributions of the photofragments have been observed.

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).

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.

Many-body effects can impact on rates of energy transfer from a ‘hot’ DF solute to acetonitrile solvent.

Tris(dimethylamino)silane catalytically dissociates on W and Ta surfaces to form ˙CH₃ and H₃C–NCH₂, favored at low and high temperatures, respectively.

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.

First measurements of Al⁺ ion reaction kinetics relevant to meteor-ablated metal chemistry in planetary upper atmospheres.

Laser photodissociation experiments on gas-phase protonated and deprotonated oxybenzone reveal how the absorption properties and photodegradation products are significantly affected by pH.

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).

Collisions between metastable neon and ammonia result in either dissociative or Penning ionisation. Neither process exhibits a steric effect.

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.

Rotational product-pair correlations have been observed, while ND₃ was rotationally excited, D₂ was simultaneously rotationally excited and de-excited.

The significance of removal of atmospheric ammonia and amines by reaction with Criegee intermediates is assessed by kinetic studies.

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.

We present a comprehensive experimental study into the dissociative electron ionization dynamics of CF₃I at energies ranging from 20 to 100 eV.

Propynal (HCCCHO) is a compound of considerable astrochemical interest and observed in several interstellar objects.

The dissociative electron attachment dynamics of atmospherically important chlorine dioxide (OClO) is unravelled for the first time using velocity slice imaging.

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.

Low temperature reactions between laser-cooled Be⁺(²S_1/2) 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.

A new ketene + H₂ channel in CH₃CHO photolysis is not modelled by quasi-classical trajectories over the transition state.

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.

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.

Photofragment imaging provides a sensitive method for detection of the O₂ A′³Δ_u Herzberg III state using a one-laser dissociation/ionization scheme combined with velocity map imaging of atomic oxygen photofragments.

Photodissociation experiments are used to study two- and three-body fragmentation by collecting fragments in coincidence.

UV excitation of cold acetaldehyde cations prepared by single-photon VUV ionization results in remarkably rich photochemistry.

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.

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.

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.

The I⁻·ICF₃ complex, a frontside attack pre-reaction complex of a classic S_N2 reaction, is produced and studied using photoelectron spectroscopy.

Nearest lines plot, making assignment of dense and complex spectra easy.

The choice of ab initio electronic structure method is an important factor in determining the fidelity of nonadiabatic dynamics simulations.

Predissociation dynamics of the phenol–water dimer were studied by detecting H₂O fragments and using VMI to infer internal state distributions.

The photodissociation of deuterium iodide is catalyzed by the electric field supplied by nonresonant IR photons.

Molecular beams experiments and ab initio theory reveal indirect formation of protonated water clusters by ionization of pinene.

A general algorithm for determining diabatic representations from adiabatic energies, energy gradients and derivative couplings using neural networks is introduced.

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.

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.

The differential steric effect for spin–orbit changing collisions of NO with Ar is determined for the first time.

Two metastable dimers are created inside superfluid helium and studied using infrared spectroscopy to provide insight into condensed phase structures.

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.

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.

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 was investigated in search of unimolecular elimination of BrI via a primary channel using cavity ring-down absorption spectroscopy (CRDS) at 248 nm.

Product pair-correlated distributions in the title reactions are revealed by imaging the state-tagged CH₂D(ν₄ = 1) products.

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.

The isomer specific detection of complex hydrocarbons from irradiated methane ice plus their yields and formation routes have been elucidated.