Product state distributions of the CO produced in 308-nm photolysis acetaldehyde show clear evidence two dissociation mechanisms. One is attributed to conventional transition mechanism predicted by theory, with high rotational and translational energy a pronounced v(perpendicular)J vector correlation. However, as much 15% reaction flux proceeds via another pathway that produces low energy, very CH(4) internal no correlation between velocity angular momentum vectors. The attributes this...

Reaction pathways that bypass the conventional saddle-point transition state (TS) are of considerable interest and importance. An example such a pathway, termed "roaming," has been described in photodissociation H(2)CO. In combined experimental theoretical study, we show roaming important 308-nm CH(3)CHO to CH(4) + CO. The product is found have extreme vibrational excitation, with distribution peaked at approximately 95% total available energy. Quasiclassical trajectory calculations on...

Niobium pentoxide reacts actively with concentrate NaOH solution under hydrothermal conditions at as low 120 °C. The reaction ruptures the corner-sharing of NbO7 decahedra and NbO6 octahedra in reactant Nb2O5, yielding various niobates, structure composition niobates depend on temperature time. morphological evolution solid products 180 °C is monitored via SEM: fine Nb2O5 powder aggregates first to irregular bars, then niobate fibers an aspect ratio hundreds form. are microporous molecular...

Current atmospheric models underestimate the production of organic acids in troposphere. We report a detailed kinetic model photochemistry acetaldehyde (ethanal) under tropospheric conditions. The rate constants are benchmarked to collision-free experiments, where extensive photo-isomerization is observed upon irradiation with actinic ultraviolet radiation (310 330 nanometers). quantitatively reproduces experiments and shows unequivocally that keto-enol photo-tautomerization, forming vinyl...

Curcumin can act as a multicolor photoinitiator in free radical photopolymerization under air upon exposure to household LED bulbs.

The results are reported for a series of measurements the propagation rate coefficient (kp) butyl acrylate obtained from pulsed-laser polymerization (PLP). Previous attempts in literature to use PLP this monomer have failed because data did not satisfy internal consistency tests afforded by PLP. problem was obviated carrying out at very low temperatures and with short times between laser pulses. Data kp were over range −65 −7 °C which (invariance apparent value pulse frequency, etc.). fit...

The photofragment internal and translational energy distributions resulting from the 193 nm photolysis of acetone have been measured. Vacuum-ultraviolet laser-induced fluorescence was used to probe CO fragment, multiphoton ionization time-of-flight mass spectrometry CH3. A Boltzmann distribution observed fit each degree freedom with following characteristic temperatures: CO: Tvib =2700 K, Trot =3000 Ttrans K; CH3: =800 =500 =3500 K. No evidence found for two distinct CH3 populations, as...

The concentrations of organic acids, key species in the formation secondary aerosols, are underestimated by atmospheric chemistry models a factor ∼2. Vinyl alcohol (VA, CH2═CHOH, ethenol) has been suggested as precursor to formic acid, but sufficient tropospheric sources VA have not identified. Here, we show that is formed upon irradiation neat acetaldehyde (CH3CHO) actinic ultraviolet region, between 295 and 330 nm. Besides well-known photochemical products CO CH4, infer up 15% quantum...

We attribute the two product-state distributions previously seen in CH₃CHO photodissociation to CH₃-roaming and H-roaming, unifying all previous experimental results.

Organic acids play a key role in the troposphere, contributing to atmospheric aqueous-phase chemistry, aerosol formation, and precipitation acidity. Atmospheric models currently account for less than half observed, globally averaged formic acid loading. Here we report that acetaldehyde photo-tautomerizes vinyl alcohol under atmospherically relevant pressures of nitrogen, actinic wavelength range, λ = 300-330 nm, with measured quantum yields 2-25%. Recent theoretical kinetics studies show...

In Pérez-Peña et al. (DOI: https://doi.org/10.1039/d3ea00120b), we used a suite of box model simulations to determine how trifluoroacetaldehyde (CF 3 CHO) produced from HFO-1234ze is lost in the atmosphere and much fluoroform (CHF or HFC-23) could potentially be as result. For first time any modelling study, our included both minor CF CHO photolytic loss channel leading CHF production physical removal via wet dry deposition. their comment, Sulbaek Andersen, Nielsen, Franklin query...

The vibronic spectroscopy of the S1(1B2u)–S0(1Ag) transition p-difluorobenzene (000 at 36 838 cm−1) cooled in a supersonic free jet expansion argon has been reinvestigated some detail. Analysis over 50 transitions using fluorescence excitation and dispersed single level led to establishment or confirmation assignments 19 S1 S0 frequencies, including eight previously unassigned vibrational reassignment two one frequencies. Several Franck–Condon forbidden have identified. Their activity S1–S0...

Even in small molecules, the influence of electronic state on rotational and vibrational product energies is not well understood. Here, we use experiments theory to address this issue photodissociation formaldehyde, H2CO, radical products H + HCO. These result from dissociation singlet ground or first excited triplet (T1) H2CO. Fluorescence spectra reveal a sudden decrease HCO energy with increasing photolysis accompanied by substantial excitation. Calculations distribution using an ab...

The gas-phase laser-induced fluorescence (LIF) spectrum of a 1-phenylpropargyl radical has been identified in the region 20800−22000 cm-1 free jet. was produced from discharges hydrocarbons including benzene. Disregarding C2, C3, and CH, this appears as most strongly fluorescing product visible wavelength two-dimensional excitation−emission jet-cooled benzene discharge. structure carrier elucidated by measurement matching resonant two-color two-photon ionization at m/z = 115 density...

Dynamically adjusting the weights in state-averaged multiconfigurational self-consistent field (SA-MCSCF) calculations using an energy-dependent functional allows electronic wave function to smoothly evolve across potential energy surface (PES) and correctly preserves differing asymptotic electronic-state degeneracy patterns. We have developed a generalized dynamic weighting (GDW) method treat high-lying states. To test method, global PES was constructed for S2 (B̃) state of CHF (CDF), which...

Extracellular matrix (ECM) remodeling contributes to the pathogenic changes in chronic obstructive pulmonary disease (COPD) and is both complex not well understood. Collagen I, a component of ECM altered COPD airways, has second harmonic generation (SHG) properties. The SHG signal coherent, propagating forward (F) (primarily organized/mature collagen fibrils) backward (B) disorganized/immature parallel incident light. F/B ratio was used determine proportion organized disorganized collagen,...

Photofragment excitation (PHOFEX) spectra of the jet-cooled formyl (HCO and DCO) radical have been measured by monitoring laser-induced fluorescence CO fragment. The following Ã(A″)←X̃(A′) vibronic transitions were measured: (v1,v2,v3)←(0,0,0) where for HCO v2=6–16 with v1,v3=0; v2=7–12 v1=1, v3=0; v2=9–12 v1=0, v3=1 DCO v2=14–18 v1,v3=0. PHOFEX technique provides a powerful method discriminating against strong so as to allow assignment measurement many weaker Franck–Condon bands....

The dynamics of the photodissociation CH(3)CHO into CH(3) + HCO products have been investigated at energies between 30,953 and 31,771 cm(-1), spanning threshold for radical production on triplet (T(1)) surface. A barrierless pathway to formed ground state (S(0)) surface was discovered established be an important reaction channel in acetaldehyde throughout this wavelength range. laser induced fluorescence (LIF) spectra recorded from dissociated above below T(1) barrier energy are quite...

Student experience surveys have become increasingly popular to probe various aspects of processes and outcomes in higher education, such as measuring student perceptions the learning environment identifying that could be improved. This paper reports on a particular survey for evaluating individual experiments has been developed over some 15 years part large national Australian study pertaining area undergraduate laboratories—Advancing Science by Enhancing Learning Laboratory. development...

Multihydroxy-anthraquinone derivatives [i.e., 1,2,4-trihydroxyanthraquinone (124-THAQ), 1,2,7-trihydroxyanthraquinone (127-THAQ), and 1,2,5,8-tetrahydroxyanthraquinone (1258-THAQ)] can interact with various additives [e.g., iodonium salt, tertiary amine, N-vinylcarbazole, 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine] under household green LED irradiation to generate active species (cations radicals). The relevant photochemical mechanism is investigated using quantum chemistry,...

The dynamics of CO production from photolysis H2CO have been explored over a 8000 cm−1 energy range (345 nm–266 nm). Two-dimensional ion imaging, which simultaneously measures the speed and angular momentum distribution photofragment, was used to characterise rotational translational quantify branching fraction roaming, transition state (TS), triple fragmentation (3F) pathways. for TS channel broadens significantly with increasing energy, while is relatively constant roaming channel. also at...

Since its discovery 16 years ago, roaming has become a ubiquitous mechanism in molecular photochemistry. Its general features are now understood, but little detail is known about how the potential energy surface (PES) determines reaction outcomes. We performed detailed experiments on formaldehyde (H2CO) photodissociation and determined fully correlated quantum state distributions of hydrogen carbon monoxide products. These reveal previously undetected bimodal rotational distributions....