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The comprehensive picture of the fragmentation behaviour of H2S has been provided by detecting the H, S(1D) and S(1S) atom products at wavelengths 155–120 nm.

We use pressure as a powerful tool to modulate the photoluminescence properties of the 2D perovskite (2meptH2)PbCl4. The rare, high-brightness, “warm” white light emission was successfully realized via a pressure-inhibited nonradiative transition.

A vacuum ultraviolet free electron laser (VUV-FEL) photoionization aerosol mass spectrometer (AMS) has been developed for online measurement of neutral compounds in laboratory environments. The aerosol apparatus is mainly composed of a smog chamber and a reflectron time-of-flight mass spectrometer (TOF-MS). The indoor smog chamber had a 2 m

Vibrational-state dependent decay dynamics of 2-pyridone excited to the S1 electronic state is revealed by a time-resolved photoelectron spectroscopy study.

State-to-state photodissociation of CO2(v2 = 0 and 1) at 157 nm via the O(1D) + CO(X1Σ+) channel was studied by using the sliced velocity map imaging technique.

Using a readily accessible and high-efficiency photocatalyst for inducing chemical transformations is highly desirable. All inorganic lead halide perovskites (APbX3, X = Cl, Br, I) are utilized intensively in photovoltaics providing outstanding optoelectronic performance and are easy-to-process, but their use in organic synthesis is still in its infancy. Herein, we report a facile protocol for the photocatalytic oxidation of a series of amines and sulfides to their corresponding imines and sulfoxides with excellent yields and selectivity using CsPbBr3 as a visible-light catalyst. The result show that amines bearing electron-donating groups give rise to aldehydes as the final products, while amines with electron-withdrawing groups afford imines as the major products. Reaction mechanism studies reveal that the photogenerated holes (h+), superoxide radicals (O2˙−) and singlet oxygen are involved in the reaction performed in air and O2 atmospheres. In addition, for the reaction conducted under anaerobic conditions, free radicals generated by amines plays a vital role in determining the transformation of amines to imines.

A facile and efficient visible-light-mediated method for directly converting sulfides into sulfoxides under clean conditions without using any photocatalysts is reported. This method exhibited favourable compatibility with functional groups and afforded a series of sulfoxides with high selectivity and yields. Moreover, in order to shed more light on such a transformation, detailed mechanism studies were carried out both experimentally and theoretically. The readily accessible, low-cost and eco-friendly nature of the developed method will endow it with attractive applications in chemical synthesis.

The excited-state decay dynamics of 2-ethylpyrrole following UV excitation in the wavelength range of 254.8-218.0 nm is investigated in detail using the femtosecond time-resolved photoelectron imaging method. The time-resolved photoelectron spectra and photoelectron angular distributions at all pump wavelengths are carefully analysed and the following picture is derived: at the longest pump wavelengths (254.8, 248.3 and 246.1 nm), 2-ethylpyrrole is excited to the S1(1πσ*) state having a lifetime of about 50 fs. At 248.3, 246.1 and 237.4 nm, another excited state of Rydberg character is excited. The lifetime of this state is ∼570 fs at 237.4 nm and becomes slightly longer at other two pump wavelengths. At the shortest pump wavelengths (230.8 and 218.0 nm), 2-ethylpyrrole is excited to a state which is tentatively assigned to the 11ππ* state, having a lifetime of 75 ± 15 and 48 ± 10 fs for the longer and shorter pump wavelengths, respectively. Internal conversion to the S1(1πσ*) state might be one of the decay mechanisms of the 11ππ* state.

Photodissociation dynamics of H2O and D2O via the state by one-photon excitation have been investigated using the H/D atom Rydberg tagging time-of-flight technique. The TOF spectra of the H/D-atom product in both parallel and perpendicular polarizations have been measured. Product translational energy distributions and angular distributions have been derived from TOF spectra. By simulating these distributions, quantum state distributions of the OH/OD product as well as the state-resolved angular anisotropy parameters were determined. The most important pathway of H2O/D2O dissociation via the state leads to highly rotationally excited OH/OD(X, v = 0) products, while vibrationally excited OH/OD products with v ≥ 1 comprise only one third of the total OH/OD(X) population. The branching ratios of OH(A)/OH(X) and OD(A)/OD(X) have also been determined, 1.0/3.0 for H2O at 122.12 nm and 1.0/2.2 for D2O at 121.95 nm, which are reasonably consistent with the values predicted by the previous theory.

State-to-state photodissociation of carbon dioxide (CO2) via the 3p1Πu Rydberg state was investigated by the time-sliced velocity map ion imaging technique (TSVMI) using a tunable vacuum ultraviolet free electron laser (VUV FEL) source. Raw images of the O(1S) products resulting from the O(1S) + CO(X1Σ+) channel were acquired at the photolysis wavelengths between 107.37 and 108.84 nm. From the vibrational resolved O(1S) images, the product total kinetic energy releases and the vibrational state distributions of the CO(X1Σ+) co-products were obtained, respectively. It is found that vibrationally excited CO co-products populate at as high as v = 6 or 7 while peaking at v = 1 and v = 4, and most of the individual vibrational peaks present a bimodal rotational structure. Furthermore, the angular distributions at all studied photolysis wavelengths have also been determined. The associated vibrational-state specific anisotropy parameters (β) exhibit a photolysis wavelength-dependent feature, in which the β-values observed at 108.01 nm and 108.27 nm are more positive than those at 107.37 nm and 107.52 nm, while the β-values have almost isotropic behaviour at 108.84 nm. These experimental results indicate that the initially prepared CO2 molecules around 108 nm should decay to the 41A' state via non-adiabatic coupling, and dissociate in the 41A' state to produce O(1S) + CO(X1Σ+) products with different dissociation time scales.

The ultrafast decay dynamics of water molecules excited to ′1B1 and ′′1A2 states is studied by combining two-photon excitation and time-resolved photoelectron imaging methods. The lifetime of the ′1B1(000) state of H2O (D2O) is determined to be 1.54 ± 0.1 (22.6 ± 1.6) ps, consistent with a previous high-resolution spectroscopic study. The H2O ′′1A2(000) state decays with a lifetime of 4.1 ± 0.2 ps, while in the D2O ′′1A2(000) state, two independent decay pathways are observed, with time constants of 0.55 ± 0.1 and 13 ± 1 ps, respectively. The former is proposed to be associated with a hitherto undocumented ′′ → pathway, induced by Coriolis interaction.

The knowledge of intramolecular vibrational energy redistribution (IVR) and structural dynamics of rhenium photo-catalysts is essential for understanding the mechanism of the photo-catalytic process of CO2 reduction. In this study, the rhenium compound Re(dcbyp)(CO)3NCS (Re-NCS), which served as a model CO2 reduction catalyst, was investigated using two dimensional infrared (2D IR) spectroscopy. The vibrational relaxation dynamics and rotational dynamics of Re-NCS were measured by monitoring both the CO and NCS vibrational modes. The rotational dynamics measurement of the CO vibrational stretch shows a single exponential decay with a time constant of 140 ± 10 ps. In contrast, a bi-exponential decay is needed to describe the rotational dynamics of the NCS stretching mode with time constants of 1.5 ± 0.3 ps and 189 ± 15 ps. The 2D IR experiment indicated that the carbonyl CO vibrational modes in Re-NCS are strongly coupled. Furthermore, the intramolecular vibrational energy transfer between CO and NCS stretching modes was observed and analyzed based on an energy exchange model. The energy down flowing transfer from CN to CO stretching mode was determined using time constants of 50 ps. The relatively slow intramolecular vibrational energy transfer rate suggests that there is a weak coupling between CO and NCS ligands. Further theoretical calculation showed that the coupling strength between CO and CN is relatively weak and is about 5-6 times smaller than the coupling strength between the CO vibrational modes in Re-NCS. The distinct structural dynamics of the NCS ligand in Re-NCS presented in this study should provide a fundamental understanding of the role of an anionic ligand in rhenium photo-catalysts, which is believed to play an important role in the photo-catalytic reduction of CO2.

The ultrafast excited-state dynamics of 2,5-dimethylpyrrole following excitation at wavelengths in the range of 265.7-216.7 nm is studied using the time-resolved photoelectron imaging method. It is found that excitation at longer wavelengths (265.7-250.2 nm) results in the population of the S1(1πσ*) state, which decays out of the photoionization window in about 90 fs. At shorter pump wavelengths (242.1-216.7 nm), the assignments are less clear-cut. We tentatively assign the initially photoexcited state(s) to the 1π3p Rydberg state(s) which has lifetimes of 159 ± 20, 125 ± 15, 102 ± 10 and 88 ± 10 fs for the pump wavelengths of 242.1, 238.1, 232.6 and 216.7 nm, respectively. Internal conversion to the S1(1πσ*) state represents at most a minor decay channel. The methyl substitution effects on the decay dynamics of the excited states of pyrrole are also discussed. Methyl substitution on the pyrrole ring seems to enhance the direct internal conversion from the 1π3p Rydberg state to the ground state, while methyl substitution on the N atom has less influence and the internal conversion to the S1(πσ*) state represents a main channel.

The effects of CH stretching excitation on the reactivity of the F + CHD3 → HF + CD3 reaction were studied experimentally using crossed-beam and time-sliced velocity map imaging techniques over the collision energy range of 1.21 to 9.00 kcal mol−1. The experimental results showed that the CH stretching excitation promoted its cleavage and enhanced the title reaction at low collision energies. This enhancement dropped with an increase of the collision energy. And at high collision energies, CH stretching excitation appeared to lower the reactivity of the above reaction, in contrast to the case at low collision energies. This decreasing trend in the enhancement of reactivity was in agreement with previous theoretical studies. The vibrationally excited reaction was further compared with the ground-state reaction at a same total reagent energy of 9.80 kcal mol−1, and similar reactivities were derived.

The predissociation dynamics of water molecules in the electronic state were studied using the time-resolved photoelectron imaging method. Both vibrationless and vibrationally excited states in the electronic state were studied, with an emphasis on the vibrational excitation effects on the predissociation dynamics of the state. Besides the well-known rotationally and non-rotationally mediated predissociation pathways (Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 19148), an accidental resonance mediated predissociation pathway for the first bending mode excited state in the electronic state of H2O is revealed, providing an excellent example of competition between non-adiabatic decay pathways involving at least five electronic states.

Herein, we discuss the study of solvation dynamics of lithium-succinonitrile (SN) plastic crystalline electrolytes by ultrafast vibrational spectroscopy. The infrared absorption spectra indicated that the CN stretch of the Li(+) bound and unbound succinonitrile molecules in a same solution have distinct vibrational frequencies (2276 cm(-1)vs. 2253 cm(-1)). The frequency difference allowed us to measure the rotation decay times of solvent molecules bound and unbound to Li(+) ion. The Li(+) coordination number of the Li(+)-SN complex was found to be 2 in the plastic crystal phase (22 °C) and 2.5-3 in the liquid phase (80 °C), which is independent of the concentration (from 0.05 mol kg(-1) to 2 mol kg(-1)). The solvation structures along with DFT calculations of the Li(+)-SN complex have been discussed. In addition, the dissociation percentage of lithium salt was also determined. In 0.5 mol kg(-1) LiBF4-SN solutions at 80 °C, 60% ± 10% of the salt dissociates into Li(+), which is bound by 2 or 3 solvent molecules. In the 0.5 mol kg(-1) LiClO4-SN solutions at 80 °C, the salt dissociation ratio can be up to 90% ± 10%.