Xα–DV Modeling of Photoionization and Electronic Absorption Spectra of Cobalt tris–Acetylacetonate

Ionization energies, excited state energies, and oscillator strengths of electron–dipole transitions are calculated within the framework of the SCF–X–DV quantum–chemical model of the Co(HCOCHHCO)₃ model complex in order to interpret the photoionization and electronic absorption spectra of cobalt tris––diketonate. It is shown that the sequences of ionization and excitation energies calculated in the transition state approximation do not significantly differ from the sequence of energies estimated in the frozen MO approximation. The model absorption spectrum with a correction of 1.9 eV applied to the energy of the vacant ₄ ^* orbital is in good agreement with our gas–phase absorption spectrum of Co(acac)₃.     

Experimental observation of the intense enhancement of metal sonoluminescence under pressure and temperature

The multibubble sonoluminescence spectra of argon-saturated aqueous salt solutions of alkaline and alkaline earth metals exhibit an intense enhancement of atomic emission with respect to continuum emission with an increase in the hydrostatic pressure and decrease in the solution temperature. It is suggested that ion reduction and metal atom excitation occur in the incandescent liquid layer formed at the liquid/bubble interface during a time interval that is sufficiently short for diffusion. The layer volume and, therefore, the number of “trapped” metal ions increases with an increase in the finite temperature in the cavitation bubble, which is caused by external factors.     

Modeling of the Electronic Absorption Spectra and Photoionization of Scandium and Titanium Tris(acetylacetonates) by the DV-XαMethod

In order to interpret the electronic absorption spectra of titanium tris(-diketonates) and to establish the correlation between the ionization and excitation energies, the oscillator strengths and energies and the ionization energies for the model complexes M(Mal)₃(Mal is deprotonated malonodialdehyde, M = Sc, Ti) were calculated in the transition state approximation of the DV-Xmethod. The good agreement between the calculated photoelectron spectra and the experimental data and the correlation found between two types of excitation justified the assignment of the experimental absorption bands to the electronic states of Ti(Acac)₃.     

Determination of Lifetime of Ce3+ Luminescence by Time-Correlated Single Photon Counting Method during Sonoluminescence from Aqueous CeCl3 Solution

Optics and Spectroscopy - Using a counter for single photon correlations, the flashes of sonoluminescence and sonophotoluminescence of a 0.1 M aqueous solution of CeCl3 are separated by time. The...     

Excited states and absorption spectra of β-diketonate complexes of boron difluoride with aromatic substituents

In the approximation of the time-dependent electron density functional theory, we have studied using the quantum-chemical method the nature of excited states of boron difluoride acetylacetonate F₂BAA and its substituted derivatives that contain aromatic groups with one or two benzene cycles in the β-position. Optimization of the geometry of complexes show coplanar positions of cycles for all compounds, except for that with the substituent C₆H₃(CH₃)₂. Based on the calculated transition energies and oscillator strengths, we have simulated the absorption spectra in the prevacuum range. The calculated absorption spectra have been compared with the experimental spectra in the gas phase or in solutions. We show that, in the absorption spectra of complexes that contain substituents with one benzene cycle, the first three bands are caused by the transition of π electrons of the substituent to the LUMO of the chelate cycle. In complexes with two cycles in the substituent, the number of these transitions increases to five. As the π system becomes more extended, a bathochromic shift of the first absorption band and an increase in the transition probability are observed.     

Electronic structure and photoelectron spectra of osmium and ruthenium tetraoxides

The X-SW method has been used in the nonrelativistic and quasirelativistic approximations to calculate the electronic structures of OsO₄, RuO₄, and FeO₄. When the 5d element is replaced by a 4d or 3d one, the electron-density redistribution is due mainly to the d electrons. All the d electrons in FeO₄ are localized on the iron atom, which markedly reduces the ionic and covalent bonding on the transition from RuO₄, to FeO₄, which explains the instability of FeO₄. The calculated spin-orbit splittings agree well with the structure of the PES bands, which enables one to establish the sequence of MO ionization energies unambiguously.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 23, No. 4, pp. 456–461, July–August, 1987.     

The Photochemical Behavior of Nalidixic Acid

The influence of intermolecular proton transfer on the spectral properties of nalidixic acid (nlqH) in the ground and excited electronic states was studied. A scheme of possible protolytic reactions that occurred in this compound under the action of pH and UV radiation in aqueous medium was constructed. The total energies of model nlqH molecules in the monomeric and dimeric states were calculated quantum-chemically. Proton transfer was found to substantially influence the radiation capacity of nlqH related to the protonation and dimerization of molecules. Original Russian Text ? A.V. Polishchuk, M.V. Kazachek, E.T. Karaseva, V.E. Karasev, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 4, pp. 754–758.     

Time-Correlated Photon Counting for Estimating the Duration of Na-Line and Continuum Emission Flashes in the Spectra of Multi-Bubble Sonoluminescence

Optics and Spectroscopy - The time-correlated photon counting technique using software is used to estimate the duration and succession of Na-line and continuum emission flashes upon irradiation of...