Themed collection Ultrafast chemical dynamics

Introduction to the themed issue of PCCP on ultrafast chemical dynamics.

Transient electron density maps are directly measured by femtosecond X-ray powder diffraction in potassium dihydrogen phosphate (KDP).

Transient absorption spectroscopy reveals the ultrafast excited-state relaxation dynamics and efficient, picosecond-scale intersystem crossing kinetics of three closely-related phenylthiophene compounds.

We perform QM/MM molecular dynamics simulations on [Pt₂(P₂O₅H₂)₄]⁴⁻. This is used to calculate the ground state X-ray absorption spectrum of the complex, showing a significant solvent effect, which has possible important implications for the structural analysis of molecules in solution.

Fluorescence anisotropy dynamics are measured in star-shaped fluorene molecules. Two processes are observed: a fast 500 fs depolarisation assigned to exciton localisation, and a slower 3–8 ps process associated with energy transfer between arms.

The Paternò–Büchi reaction is studied in an isolated molecule with femtosecond time-resolution, using the [2.2]paracyclophane molecular scaffold.

A comparative transient absorption study of a Zn-porphyrin monomer and its corresponding dimer shows the influence of excitonic coupling on temporal relaxation.

Differential transmission of CdSe/CdS nanorod samples with different core sizes was measured, excitation resonant to the core transition. The bleaching ratio between dot and rod transitions increases with dot size.

Distinct ultrafast equilibrium fluctuations of different ferric haem protein conformational substates are revealed using 2D-IR spectroscopy.

I⁻(H₂O)₅ photoinduced electron transfer: the excited electron detaches rapidly from the iodine atom and is subsequently stabilized by the gradual iodine-driven reorganization of the water cluster moiety.

Protein dynamics dominate the THz permittivity for T < 265 K showing that motions most dependent on the dynamical transition are on the >1 ps time scale.

The molecular motions singled out by a novel kind of spectroscopy are simulated and identified for the first time.

Rotational dynamics of chaotropic thiocyanate ions in highly concentrated aqueous solutions studied by IR pump–probe spectroscopy.

A dark ¹nπ* state is observed in UV-excited cytosine polymers and its lifetime is lengthened relative to the monomer.

We report an investigation of aqueous solutions of TMAO and TBA as a function of concentration and temperature using the ultrafast optically heterodyne detected optical Kerr effect.

The energy flow from a bend-vibrationally excited water molecule in aqueous solution can be followed in molecular detail via a Poisson bracket work and power formulation. The bend energy decay, in red, is associated with a dominant energy transfer to water rotation, rather than to translation.

The reorientation dynamics of water hydrating cations and anions are studied with femtosecond mid-infrared spectroscopy. It is found that ions influence the dynamics of the hydration shells of their counter-ions.

Ultrafast deactivation of imidazole following UV excitation is investigated experimentally by probing multiple photoproducts.

Exploiting the combination of ultrafast transient absorption measurements (sub-10 fs time resolution) and quantum chemical DFT//TDDFT calculations we investigate the ultrafast dynamics in a low band gap polymer (PCPDTBT) of great interest for organic photovoltaics, rationalizing the internal conversion photophysical processes occurring after photoexcitation.

Sub-10 fs deep-ultraviolet pulses are utilized in the ultrafast spectroscopy for the first time.

Schematic potential energy surface for the photoinitiated trans → cis isomerization of 4-nitro-4′-dimethylamino-azobenzene showing the initial dilation of the CNN bend followed by quick torsional motions.

The infrared pump–probe signal of the asymmetric stretching mode in D₂O shows an oscillatory component with a wavenumber of 80 cm⁻¹, which is assigned as an intermolecular mode.

Environment dependence of ultrafast excited state dynamics in spheroidene and appearance of an intermediate state in the case of a low polarizability solvent.

Femtosecond fluorescence of cis-stilbene showed two components from different potential regions and indicated isomerization/cyclization branching occurring before the CC twisting.

A new technique for ultrashort laser studies of biomolecules, liberated into the gas phase via laser induced acoustic desorption (LIAD).

The photodissociation dynamics of azide radicals from an iron complex are studied with femtosecond UV-pump–mid-IR probe spectroscopy.

Two dimensional vibrational echo and FTIR spectroscopy supported by DFT calculations reveal contact ion pairs in caesium oxalate solutions.

The galvinoxyl free radical converts 3 eV (70 kcal mol⁻¹) of electronic energy within less than 200 femtoseconds into vibrational energy.

Ultrafast probes are combined to study spin state photo- switching dynamics in two spin-crossover molecular polymorphs.

Isotropic and anisotropic 2D-IR spectra of neat ice Ih, reporting on the couplings that give rise to its peculiar lineshape.

The B ¹B₁ state of c-C₃H₂ has been investigated by femtosecond time-resolved photoelectron spectroscopy.

Two-dimensional infrared correlation spectra show significant differences in the coupling networks of anomers that vary at a single stereochemical center.

Quantum dynamical simulations of carbon vapor show that nonadiabatic electronic stopping leads to fast aggregation of C₂ molecules into carbon nanostructures.

Ab initio molecular dynamics is used to unravel the different pathways that (4-methylcyclohexylidene) fluoromethane undergoes after light irradiation.

Femtosecond mid-infrared spectroscopy is used to study the vibrational relaxation of water molecules constituting a so-called water bridge.