High-Temperature Collision Integrals for m-6-8 and Hulburt–Hirschfelder Potentials

This study is aimed to determine collision integrals for atoms interacting according to the m-6-8 and Hulburt–Hirschfelder potentials and analyze the differences between potentials. The precision of four significant digits was reached at all tested temperatures, and for high-temperature applications, six digits were calculated. The proposed method was tested on the Lennard-Jones potential and found to excellently agree with the recent high-quality data. In addition, the Hulburt–Hirschfelder potential was used for determining the collision integrals of the interaction of nitrogen atoms in the ground electronic state and compared with other known values. The calculations were performed using Mathematica computation system which can deal with singularities (so-called orbiting).

Ground electronic state description of thiourea coordination in homoleptic Zn2+, Ni2+ and Co2+ complexes using sulfur K-edge X-ray absorption spectroscopy

Sulfur K-edge X-ray absorption spectroscopy (XAS) was employed to experimentally characterize the coordinative bond between the thiourea (TU) or thiocarbamide ligand and transition metal (TM) ions Zn2+, Co2+ and Ni2+ in distorted tetrahedral and octahedral homoleptic coordination environments. Comparisons of XAS spectra of the free TU ligand and [Zn(TU)4]2+, [Co(TU)4]2+ and [Ni(TU)6]2+ complexes clearly identify spectral features unique to TM2+–S(TU) bonding. Quantitative analysis of pre-edge intensities describes the covalency of Ni2+—S(TU) and Co2+—S(TU) bonding to be at most 21% and 9% as expressed by the S 3p contributions per TM 3d electron hole. Using relevant Ni2+ complexes with dithiocarbamate and thioether ligands, we evaluated the empirical S 1s → 3p transition dipole integrals developed for S-donor ligands and their dependence on heteroatom substitutions. With the aid of density functional theory-based ground electronic state calculations, we found evidence for the need of using a transition dipole that is dependent on the presence of conjugated heteroatom (N) substitution in these S-donor ligands.

Time-Resolved Study of Light-Induced Ground State Proton Transfer from Acid Medium to 4-Nitrophenolate

In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO^-) in the ground electronic state and subsequent proton transfer reaction with acetic acid and water with numerical calculations and laser flash photolysis. We employ the Debye-Smoluchowski spherically-symmetric diffusion model of photoacid proton transfer to determine experimental conditions for studying thermally activated chemical reactions in the ground electronic state. Numerically calculated protonation and deprotonation probabilities for 4-NPO^- and 4-nitrophenol (4-NPOH) in both ground and excited states showed the feasibility of efficiently producing the ground state anion in the photoacid cycle. We performed laser flash photolysis measurements of 4-NPOH to characterize the photo-initiated ground state protonation and deprotonation rate constants of 4-NPO^-/4-NPOH as a function of acetic acid, pH, temperature and viscosity. Overall, the work presented here shows a simple way to study fast competing bimolecular proton transfer reactions in non-equilibrium conditions in the ground electronic state <i>(GSPT)</i>.

Time-Resolved Study of Light-Induced Ground State Proton Transfer from Acid Medium to 4-Nitrophenolate

In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO^-) in the ground electronic state and subsequent proton transfer reaction with acetic acid and water with numerical calculations and laser flash photolysis. We employ the Debye-Smoluchowski spherically-symmetric diffusion model of photoacid proton transfer to determine experimental conditions for studying thermally activated chemical reactions in the ground electronic state. Numerically calculated protonation and deprotonation probabilities for 4-NPO^- and 4-nitrophenol (4-NPOH) in both ground and excited states showed the feasibility of efficiently producing the ground state anion in the photoacid cycle. We performed laser flash photolysis measurements of 4-NPOH to characterize the photo-initiated ground state protonation and deprotonation rate constants of 4-NPO^-/4-NPOH as a function of acetic acid, pH, temperature and viscosity. Overall, the work presented here shows a simple way to study fast competing bimolecular proton transfer reactions in non-equilibrium conditions in the ground electronic state <i>(GSPT)</i>.

Photodissociation of Iso-Propoxy (I-C3H7O) Radical at 248 Nm

<p>Photodissociation of the <i>i</i>-C₃H₇O radical is investigated using fast beam photofragment translational spectroscopy. Neutral <i>i</i>-C₃H₇O radicals are produced through the photodetachment of a fast beam of <i>i</i>-C₃H₇O^- anions and are subsequently dissociated using 248 nm (5.0 eV). The dominant product channels are CH₃ + CH₃CHO and OH + C₃H₆ with some contribution from H + C₃H₆O. CH₃ and H loss are attributed to dissociation on the ground electronic state of <i>i</i>-C₃H₇O, but in a nonstatistical manner because RRKM dissociation rates exceed the rate of energy randomization. Translational energy and angular distributions for OH loss are consistent with ground state dissociation, but the branching ratio for this channel is considerably higher than predicted from RRKM rate calculations. These results corroborate what has been observed previously in C₂H₅O dissociation at 5.2 eV that yields CH₃, H, and OH loss. Additionally, <i>i</i>-C₃H₇O undergoes three-body fragmentation to CH₃ + CH₃ + HCO and CH₃ + CH₄ + CO. These three-body channels are attributed to dissociation of <i>i</i>-C₃H₇O to CH₃ + CH₃CHO, followed by secondary dissociation of CH₃CHO on its ground electronic state.</p>