Titanium Superoxide as a Carrier of a "Long-Lived" Superoxide Anion: An Investigation.

The photoinduced generation of a superoxide anion on the surface of a semiconductor photocatalyst is usually attributed to the reduction of O with conduction-band electrons. In the current work, the reaction of TiO with O giving rise to TiO in superoxide and peroxide states has been investigated with (CAS, CCSD) and DFT (B3LYP) calculations. The ground triplet state and two substates (open-shell singlet (OSS) and closed-shell singlet (CSS)) of a doubly degenerate excited singlet state (Δ) are considered as reactive states of oxygen, participating in spontaneous or photoinduced processes, respectively.

The Nature of the Enthalpy-Entropy Compensation and "Exotic" Arrhenius Parameters in the Denaturation Kinetics of Proteins.

Protein unfolding is a ubiquitous process responsible for the loss of protein functionality (denaturation), which, in turn, can be accompanied by the death of cells and organisms. The nature of enthalpy-entropy compensation (EEC) in the kinetics of protein unfolding is a subject of debate. In order to investigate the nature of EEC, the "completely loose" transition state (TS) model has been applied to calculate the Arrhenius parameters for the unfolding of polyglycine dimers as a model process.

Self-assembling of the neutral intermediate with chemically bound argon in photoexcited van der Waals complex Ar-I.

Photodissociation of the van der Waals complex Ar-I after excitation into the Rydberg states of I has been investigated with velocity map imaging of photofragments. Formation of the translationally hot ions of argon Ar with three modes in kinetic energy distribution has been revealed. The measured dependence of the kinetic energy of Ar on the pumping photon energy indicates the appearance of Ar from three channels of the photodissociation of the linear intermediate Ar-I-I containing chemically bound argon.

Singlet Oxygen Generation via UV-A, -B, and -C Photoexcitation of Isoprene-Oxygen (CH-O) Encounter Complexes in the Gas Phase.

The formation of singlet oxygen O provided by the photoexcitation of the encounter complexes of isoprene with oxygen (CH-O) in the gas phase within the spectral region 253.5-355 nm has been observed at the elevated pressure of oxygen. Singlet oxygen has been detected with its NIR luminescence centered near 1.

Tungsten Isotope-Specific UV-Photodecomposition of W(CO) at 266 nm.

UV photodissociation of tungsten hexacarbonyl W(CO) has been studied in the molecular beam conditions using time-of-flight mass spectrometry and velocity map imaging. Irradiation of W(CO) by pulsed laser radiation at 266 nm results in the appearance of singly and doubly charged tungsten ions. The isotope composition of these ions deviates essentially from natural abundance with deviation being pulse energy-dependent.

Decomposition Pathways of Titanium Isopropoxide Ti(OPr): New Insights from UV-Photodissociation Experiments and Quantum Chemical Calculations.

The UV-photodissociation at 266 nm of a widely used TiO precursor, titanium tetraisopropoxide (Ti(OPr), TTIP), was studied under molecular-beam conditions. Using the MS-TOF technique, atomic titanium and titanium(II) oxide (TiO) were detected among the most abundant photofragments. Experimental results were rationalized with the aid of quantum chemical calculations (DLPNO-CCSD(T) and DFT).

Photodissociation of van der Waals complexes of iodine X-I (X = I, CH) via charge-transfer state: A velocity map imaging investigation.

The photodissociation of van der Waals complexes of iodine X-I (X = I, CH) excited via Charge-Transfer (CT) band has been studied with the velocity map imaging technique. Photodissociation of both complexes gives rise to translationally "hot" molecular iodine I via channels differing by kinetic energy and angular distribution of the recoil directions. These measured characteristics together with the analysis of the model potential energy surface for these complexes allow us to infer the back-electron-transfer (BET) in the CT state to be a source of observed photodissociation channels and to make conclusions on the location of conical intersections where the BET process takes place.

Singlet oxygen photogeneration from X-O₂ van der Waals complexes: double spin-flip vs. charge-transfer mechanism.

The channel of singlet oxygen O2((1)Δg) photogeneration from van der Waals complexes of oxygen X-O2 has been investigated to discriminate between two possible mechanisms based on charge-transfer (CT) or double spin-flip (DSF) transitions. The results obtained in this work for complexes with X = ethylene C2H4, 1,3-butadiene C4H6, deuterated methyl iodide CD3I, benzene C6H6 and water H2O and for those investigated previously indicate the DSF mechanism as a source of singlet oxygen. The formation of O2((1)Δg) is observed only when the energy of exciting quantum is sufficient for DSF transition.

Predissociation of high-lying Rydberg states of molecular iodine via ion-pair states.

Velocity map imaging of the photofragments arising from two-photon photoexcitation of molecular iodine in the energy range 73 500-74 500 cm(-1) covering the bands of high-lying gerade Rydberg states [(2)Π1/2]c6d;0g (+) and [(2)Π1/2]c6d;2g has been applied. The ion signal was dominated by the atomic fragment ion I(+). Up to 5 dissociation channels yielding I(+) ions with different kinetic energies were observed when the I2 molecule was excited within discrete peaks of Rydberg states and their satellites in this region.

Photodissociation of van der Waals clusters of isoprene with oxygen, C5H8-O2, in the wavelength range 213-277 nm.

The speed and angular distribution of O atoms arising from the photofragmentation of C(5)H(8)-O(2), the isoprene-oxygen van der Waals complex, in the wavelength region of 213-277 nm has been studied with the use of a two-color dissociation-probe method and the velocity map imaging technique. Dramatic enhancement in the O atoms photo-generation cross section in comparison with the photodissociation of individual O(2) molecules has been observed. Velocity map images of these "enhanced" O atoms consisted of five channels, different in their kinetic energy, angular distribution, and wavelength dependence.

Quantum yield and mechanism of singlet oxygen generation via UV photoexcitation of O2-O2 and N2-O2 encounter complexes.

The mechanism and spectral dependence of the quantum yield of singlet oxygen O(2)(a (1)Δ(g)) photogenerated by UV radiation in gaseous oxygen at elevated pressure (32-130 bar) have been experimentally investigated within the 238-285 nm spectral region overlapping the range of the Wulf bands in the absorption spectrum of oxygen. The dominant channel of singlet oxygen generation with measured quantum yield up to about 2 is attributed to the one-quantum absorption by the encounter complexes O(2)-O(2). This absorption gives rise to oxygen in the Herzberg III state O(2)(A' (3)Δ(u)), which is assumed to be responsible for singlet oxygen production in the relaxation process O(2)(A' (3)Δ(u), υ) + O(2)(X (3)Σ(g)(-)) → O(2)({a (1)Δ(g)}, {b (1)Σ(g)(+)}) + O(2)({a (1)Δ(g), υ = 0}, {b (1)Σ(g)(+), υ = 0}) with further collisional relaxation of b to a state.

Experimental measurement of the van der Waals binding energy of X-O2 clusters (X=Xe, CH3I, C3H6, C6H12).

Van der Waals binding energies for the X-O(2) complexes (X=Xe, CH(3)I, C(3)H(6), C(6)H(12)) are determined by analysis of experimental velocity map imaging data for O((3)P(2)) atoms arising from UV-photodissociation of the complex [A. V. Baklanov et al.

Ionic pathways following UV photoexcitation of the (HI)2 van der Waals dimer.

Photodissociation of the (HI)(2) van der Waals dimers at 248 nm and nearby wavelengths has been studied using time-of-flight mass spectrometry and velocity map imaging. I(2)(+) product ions with a translational temperature of 130 K and "translationally hot" I(+) ions with an average kinetic energy of E(t) = 1.24 +/- 0.

Direct mapping of recoil in the ion-pair dissociation of molecular oxygen by a femtosecond depletion method.

Time-resolved dynamics of the photodissociation of molecular oxygen, O(2), via the (3)Sigma(u) (-) ion-pair state have been studied with femtosecond time resolution using a pump-probe scheme in combination with velocity map imaging of the resulting O(+) and O(-) ions. The fourth harmonic of a femtosecond titanium-sapphire (Ti:sapphire) laser (lambda approximately 205 nm) was found to cause three-photon pumping of O(2) to a level at 18.1 eV.

Cluster-enhanced X-O2 photochemistry (X=CH3I, C3H6, C6H12, and Xe).

The effect of a local environment on the photodissociation of molecular oxygen is investigated in the van der Waals complex X-O(2) (X=CH(3)I, C(3)H(6), C(6)H(12), and Xe). A single laser operating at wavelengths around 226 nm is used for both photodissociation of the van der Waals complex and simultaneous detection of the O((3)P(J),J=2,1,0) atom photoproduct via (2+1) resonance enhanced multiphoton ionization. The kinetic energy distribution (KED) and angular anisotropy of the product O atom recoil in this dissociation are measured using the velocity map imaging technique configured for either full ("crush") or partial ("slice") detection of the three-dimensional O((3)P(J)) atom product Newton sphere.

Ultraviolet photodissociation of the van der Waals dimer (CH3I)2 revisited. II. Pathways giving rise to neutral molecular iodine.

The formation of neutral I2 by the photodissociation of the methyl iodide dimer, (CH3I)2, excited within the A band at 249.5 nm is evaluated using velocity map imaging. In previous work [J.

UV photodissociation of the van der Waals dimer (CH3I)2 revisited: pathways giving rise to ionic features.

The CH(3)I A-state-assisted photofragmentation of the (CH(3)I)(2) van der Waals dimer at 248 nm and nearby wavelengths has been revisited experimentally using the time-of-flight mass spectrometry with supersonic and effusive molecular beams and the "velocity map imaging" technique. The processes underlying the appearance of two main (CH(3)I)(2) cluster-specific features in the mass spectra, namely, I(2)(+) and translationally "hot" I(+) ions, have been studied. Translationally hot I(+) ions with an average kinetic energy of 0.