Rotational contour analysis of the electronic origin band in the emission spectrum of the orthoxylyl radical at 4683 Å

The rotational contour of the 4683 Å emission band of the o-xylyl radical was studied at high resolution. Calculations of the rotational contour of this hybrid band were made in the rigid rotor approximation for various sets of values of the excited state rotational constants and directions of the transition moment μ. Matching of computed and experimental rotational features showed that μ is oriented at +37° or ?37° with respect to the b inertial axis. The nature of the excited states of o-xylyl and the methyl-to-ring interaction are discussed with respect to these two possible assignments     

Inhibition of Bacterial Adhesion and Biofilm Formation by Seed-Derived Ethanol Extracts from Persea americana Mill

The increase in antibiotic resistance demands innovative strategies to combat microorganisms. The current study evaluated the antibacterial and antivirulence effects of ethanol extracts from Persea americana seeds obtained by the Soxhlet (SE) and maceration (MaE) methods. The UHPLC-DAD-QTOF analysis showed mainly the presence of polyphenols and neolignan. Ethanol extracts were not cytotoxic to mammalian cells (CC₅₀ > 500 µg/mL) and displayed a moderate antibacterial activity against Pseudomonas aeruginosa (IC₅₀ = 87 and 187 µg/mL) and Staphylococcus aureus (IC₅₀ = 144 and 159 µg/mL). Interestingly, no antibacterial activity was found against Escherichia coli. SE and MaE extracts were also able to significantly reduce the bacterial adhesion to A549 lung epithelial cells. Additionally, both extracts inhibited the biofilm growth at 24 h and facilitated the release of internal cell components in P. aeruginosa, which might be associated with cell membrane destabilization. Real-time PCR and agarose electrophoresis gel analysis indicated that avocado seed ethanol extracts (64 µg/mL) downregulated virulence-related factors such as mexT and lasA genes. Our results support the potential of bioproducts from P. americana seeds as anti-adhesive and anti-biofilm agents.     

Jahn—Teller effects in substituted benzene cations. V. Quadratic coupling

A calculation model is derived for taking into account quadratic, in addition to linear, coupling Jahn—Teller effects in determining vibronic energy levels and transitions. Procedures are developed for analysis of Jahn—Teller electronic spectra on this basis and the new features, with respect to the linear coupling approximation, brought about by introduction of quadratic coupling, are discussed. Vibronic analyses of the B?² A″₂-X?²E″ transitions of 1,3,5-C₆F₃H⁺₃, 1,3,5-C₆F₃D⁺₃ and 1,3,5-C₆Cl₃H⁺₃ are carried out, in particular for bands involving excitation of the mode 6 vibration. Experimental evidence for quadratic Jahn—Teller effects is obtained for the sym-trifluorobenzene ions and the linear coupling parameters D₆, ω₆ and quadratic coupling parameter q₆ are derived. Two possible orders of magnitude of the quadratic coupling strength are found to be compatible with the spectra of 1,3,5-C₆Cl₃H⁺₃. The analyses are consistent between the three ions and are not in contradiction with the general findings based on the linear approximation alone.     

Jahn—Teller effects in substituted benzene cations. IV. Intermode interactions and intensity anomalies in sym-trifluorobenzene ions

A theoretical treatment of coupling between Jahn—Teller modes is given which includes both linear and quadratic Jahn—Teller coupling. Effects of two and three mode interactions on the B?²A″₂ → X?²E″ transition of the sym-trifluorobenzene ions are studied, within the linear coupling approximation, for modes 6, 7, 8 and 9. Quadratic coupling effects are considered in a companion paper (part V). The results show that discrepancies previously noted between observed relative band intensities and those calculated on the basis of single Jahn—Teller modes cannot be accounted for by multimode interactions or by Fermi resonance effects operating in conjunction with Jahn—Teller effects. Jahn—Teller combination bands are shown to have several components, the most intense of which are assigned. Particular attention is paid to various possible assignments of the 8^0,0_{1,$\text{1}\text{2}$} and 6^0,0_{3,$\text{1}\text{2}$} vibronic transitions in the light of the multimode interaction analyses.     

The mod 2 homology of BSO

This note is about a set of generators to the mod 2 homology of BSO.

     

New electronic transitions in the N2+ ion: Rotational analysis of the D′2Πgr-A2Πui transition: Comparison of experimental and ab initio calculated molecular constants

Rotational analysis has been carried out for the first time for bands of the D′²Π_g-A²Π_u system of the N₂⁺ ion. At the same time, ab initio calculations were performed using the SCF method followed by full-valence configuration interaction calculations. Theoretical results are presented as required for interpretation of the spectra.     

Jahn—Teller effects in substituted benzene cations. III. Gas phase emission spectrum of sym-C6Cl3H+3

The gas phase emission spectrum of 1, 3, 5-C₆Cl₃H⁺₃ was obtained in a discharge tube. Vibronic analysis involving correlation of ion fundamental frequencies with those of parent molecules enables a detailed comparison to be made between the vibrational structure of the spectrum of the trichloro-ion and that of 1, 3, 5-C₆F₃H⁺₃. Analogous Jahn—Teller effects are shown to take place in the ground state of the two ions. The same linear coupling model is used and two possible solutions for D₆ and ω₆ are obtained by fitting the first two intervals in the 6^0,0_{v$\text{1}\text{2}$} progression in 1, 3, 5-C₆Cl ₃H⁺₃: (i) D₆ = 0.05 - 0.08, ω₆ = 455 - 447 cm^?1, (ii) D₆ = 0.39 - 0.49, ω₆ = 399 - 392 cm^?1. Arguments based on previously established criteria, and applied here to the case of the 1, 3, 5-C₆Cl₃H⁺₃ ion are given to select set (ii) as being far more satisfactory in interpreting the experimental data. Fitting to a larger number of bands gave D₆ = 0.45, ω₆ = 395 cm^?1. The Jahn—Teller potential energy barrier E^JT₆ = 178 cm^?1 is about three times greater than in the 1, 3, 5-trifluorobenzene ions, but sufficiently small for the dynamic Jahn—Teller effect to be operative in 1, 3, 5-C₆Cl₃H⁺₃. Some remarks are made concerning assignments in the excitation spectrum and matrix fluorescence analyses.     

New Rydberg-Rydberg transitions in N2. Identification of the d3 1Sigmag+ state

Use of a special Penning-ionization source allowed Fourier-transform recording of two previously nonobserved IR emission bands spectra at 5480 and 7630 cm(-1) arising from neutral N(2). The first of these bands is the c(4) (') (1)Sigma(u) (+)-a(") (1)Sigma(g) (+) (0,0) transition, both states involved being previously known by direct vacuum (UV) absorption spectroscopy. The second band corresponds to a d(3) (1)Sigma(g) (+)-c(4) (') (1)Sigma(u) (+) (0,0) transition, in which the upper level belongs to an up to now unidentified Rydberg state. Both the upper and lower levels are perturbed by neighboring valence state levels.     

High-resolution absorption spectrum of jet-cooled CH3Cl between 70,000 and 85,000 cm(-1): new assignments

The absorption spectrum of jet-cooled CH(3)Cl was photographed from 165 to 117 nm (or 60,000 - 85,000 cm(-1), 7.5-10.5 eV) at a resolution limit of 0.0008 nm (0.3-0.6 cm(-1) or 0.04-0.08 meV). Even in the best structured region of the spectrum, from 70,000 to 85,000 cm(-1) (8.7-10.5 eV), observed bandwidths (full width at half maximum) are large, from 50 to 150 cm(-1). No rotational feature could be resolved. The spectrum is dominated by two strong bands near 9 eV, 140 nm, the D and E bands of Mulliken [J. Chem. Phys. 8, 382 (1940)] or the spectral region D of Price [J. Chem. Phys.4, 539 (1936)]. Their relative intensity is incompatible with previous assignments, namely, to a triplet and a singlet state belonging to the same configuration. On the basis of the present ab initio calculations, those bands are now assigned to two singlet states, the (1)A(1) and (1)E excited states resulting from the 2e(3)4pe Rydberg configuration. The present calculations also reveal that the two (1)E states issued from 2e(3)4sa(1) and 2e(3)4pa(1) are quasidegenerate and strongly mixed. They should be assigned to the two broad bands near 8 eV, 160 nm, the B and C bands of Mulliken and Price. Three vibrational modes are observed to be active: the CCl bond stretch nu(3)(a(1)), and the CH(3) umbrella and rocking vibrations, respectively, nu(2)(a(1)) and nu(6)(e). The fundamental frequencies deduced are well within the ranges defined by the corresponding values in the neutral and ion ground states. The possibility of a dynamical Jahn-Teller effect induced by the nu(6)(e) vibrational mode in the (1)E Rydberg states is discussed.