Spin-orbit interactions in heterocyclic analogues of fluorene

For carbazole, dibenzofuran, and dibenzothiophene—heterocyclic analogues of fluorene containing N-H, O, and S groups, respectively—the transition dipole moments P ₀₀ ⁱ for the transitions ³ B ₂→S ₀ and ³ A ₁→S ₀ from the sublevels i=z, y, x of the triplet electronic ππ* states, which are caused by intramolecular spin-orbit (SO) interactions, are calculated. The effect that the SO coupling between the S ₀ state and highest triplet states has on the calculation results is considered. The effects exerted on the value of P ₀₀ ⁱ by such specific features of the molecular structure as the position of a heteroatom on the symmetry axis, its valence, and different constants of SO coupling in heteroatoms are discussed. The reason for the weak influence of the quantity ?_HA on the rate constant of radiative deactivation of the lowest T state is ascertained.     

The effect of the nonplanarity of heterocyclic analogues of fluorene with the phosphorus atom on spin-orbit interactions

The transition dipole moments P ₀₀ ^S for the transitions from the sublevels s=z,y, and x of the triplet electronic states ³ A″, which are caused by intramolecular spin-orbit (SO) interactions, are calculated. The calculation is carried out for molecules of heterocyclic analogues of fluorene containing phosphorus and nitrogen (namely, the groups P-H, P-C₆H₅, and N-H). The influence that the planar and nonplanar models of the molecules, as well as the substituents ?C₆H₅ and ?H at the heteroatom (HA), exert on the values of (P ₀₀ ^S )² and on the directions of the corresponding vectors is considered. The values of the component \(k_{SO^ \sim } \sum _s (P_{00}^s )^2 \) of the radiative deactivation rate constant of the T ₁ state are calculated. It is ascertained that, in the series of molecules with HA = N, O, P, and S, both the calculated values of k _SO and those experimentally determined from an analysis of the intensity distribution in fine-structure phosphorescence spectra vary little, whereas the constant of the SO coupling in the heteroatom ?_HA increases substantially along this series. The reason for the weak influence of ?_HA on values of k _SO—common for both planar and nonplanar molecules—is found.     

The effect of the heteroatom on the radiative deactivation of the lowest triplet state in heterocyclic analogues of fluorene

The vibronic transition strengths F _VSO ^s for the transitions from the spin sublevels s of the triplet state T₁ to the energy levels of the nontotally symmetric vibrations of dibenzothiophene (DB(S)) are calculated. For a series of heterocyclic analogues of fluorene (DB(S) and previously studied carbazole, dibenzofuran, and phenyldibenzophosphole), the regular features of the effect of the valence state of the heteroatom and of the spin-orbit interactions in individual atomic groups of the molecule are revealed. The factors affecting changes in the radiative deactivation rate constant of the T₁ state of the molecules studied are established. The intensity distribution of the vibronic lines in the Herzberg-Teller component of the fine structure phosphorescence spectrum of phenyldibenzophosphole is calculated taking into account different populations of the triplet sublevels.     

Quartic ghost interactions of O(N) supergravity

The quartic ghost couplings of O(N) (N ? 8) supergravity are obtained to order κ². These additional interactions which are necessary for unitarity are formally the same for all N. This pattern may be useful in the search for auxilliary fields of O(N > 2) supergravity.     

Non-resonant multophoton ionization of cyclopentane and its heterocyclic analogues

We report non-resonant multiphoton ionization time-of-flight mass spectra for cyclopentane, tetrahydrofuran, tetrahydrothiophene and pyrrolidine for 355 nm excitation over a wide range of laser intensities. Unlike the corresponding three-membered ring system, there is little dependence of the fragmentation pathways upon the laser intensity. The results also indicate that the mechanisms for the molecules studied cannot be generalized and are not necessarily related to those of the three-membered rings.     

Integral characteristics of vibronic-spin-orbit interactions in a phosphorus-containing analogue of the fluorene molecule

The strengths (P ₀₀ ^s )² and F _VSO ² of the transitions from the triplet sublevels s = z, y, and x of the electronic state ³A″ of the phenyldibenzophosphole (DB(P-Ph)) molecule are calculated taking into account the intramolecular spin-orbit (SO) and joint vibronic-spin-orbit (VSO) interactions. The contributions to the vibronic transition strengths from the SO interactions in different structural elements of the molecule (the C atoms of the dibenzene framework, the P atom, and the Ph substituent) are determined. The effect of the nonplanar nuclear configuration of the DB(P-Ph) molecule on the values of F _VSO ^s is investigated. The radiative deactivation rate constants of the k _rad ^s triplet sublevels T ^s are estimated. It is found that the vibrations of the A′(B₁) symmetry in the fine-structure phosphorescence spectrum of DB(P-Ph) occur due to both the SO coupling exclusively in the P atom and the T ^x → S₀ transition (the x axis is perpendicular to the planar dibenzene framework of the molecule) with a high (preferential) population of this triplet sublevel.     

Synthesis and antibacterial evaluation of new N- and S-glycosides analogues with dinitrophenyl-substituted heterocyclic bases

Four N- and S-glycosides 13–16 having nucleobases 7–12 binding to sugar molecules from one side and to 3,5-dinitrophenyl moieties from another side were synthesized from 3,5-dinitrobenzoic acid 2. The synthetic intermediates, hydrazide 5 and thiosemicarbazide 6 regarded as important key compounds for the synthesis of nucleobases 7–12, each was obtained by two approaches. Structures of synthesized compounds were determined spectroscopically. Antibacterial activities for synthetic intermediates and glycosides were assessed using the paper disk diffusion method against Gram-negative bacteria: Pseudomonas aeruginosa, Pseudomonas fluorescens, and Escherichia coli and Gram-positive bacteria: Bacillus cereus and Staphylococcus aureus. Some of the synthetic compounds showed variant activity against some of the microorganisms tested. Nucleobases 8–10 and 12 showed moderate to slight activity against microorganisms under test at relatively high concentration, while the N-glycosides 14 and 15 exhibited persistent effect even at lower concentrations. Commercially available antibiotics polymyxine and oxytetracycline were used as positive controls.     

The photoelectron spectra of some heterocyclic compounds which contain N,O, Cl and Br

The photoelectron spectra of 19 heterocyclic compounds, several of which are germicidal agents, containing N, O, Cl and Br have been investigated. Complete band assignments have been made for the lone-pair regions of the spectra for future reference in structure/biological-activity correlations. A detailed comparison of the carbonyl-oxygen lone-pair splitting patterns in the spectra indicates that succinimide is skeletally planar, while N-chlorosuccinimide and N-bromosuccinimide are substantially nonplanar in the gas phase.     

Photoelectron spectra of 1,2-indandione, 1,3-indandione and heterocyclic analogues

The photoelectron (He(I)) spectra of 1,2-indandione and heteroanalogues (coumarandione, thionaphthenequinone, and isatin), 1,3-indandione and heteroana     

Similarity-transformed chiral NN + 3N interactions for the ab initio description of 12C and 16O

We present first ab initio no-core shell model (NCSM) calculations using similarity renormalization group (SRG) transformed chiral two-nucleon (NN) plus three-nucleon (3N) interactions for nuclei throughout the p-shell, particularly (12)C and (16)O. By introducing an adaptive importance truncation for the NCSM model space and an efficient JT-coupling scheme for the 3N matrix elements, we are able to surpass previous NCSM studies including 3N interactions. We present ground and excited states in (12)C and (16)O for model spaces up to N(max) = 12 including full 3N interactions. We analyze the contributions of induced and initial 3N interactions and probe induced 4N terms through the sensitivity of the energies on the SRG flow parameter. Unlike for light p-shell nuclei, SRG-induced 4N contributions originating from the long-range two-pion terms of the chiral 3N interaction are sizable in (12)C and (16)O.     

Measurements of the 3ν 3 band of 14N15N16O and 15N14N16O using continuous-wave cavity ring-down spectroscopy

The absorption spectra of the 3ν₃ band of nitrous oxide isotopologues, ¹⁴N¹⁵N¹⁶O and ¹⁵N¹⁴N¹⁶O, have been measured using diode laser cavity ring-down spectroscopy in 6400–6463 and 6465–6532 cm^-1, respectively. Spectroscopic parameters and the rotational line intensities of the bands have been determined. We have applied this spectroscopic technique to the measurements of the absolute isotope ratio of those isotopologues using the absolute line intensities. PACS 32.10.Bi; 33.20.Vq; 33.70.-w; 42.55.Px; 42.62.Fi     

Triviality of Hierarchical O(N) Spin Model in Four Dimensions with Large N

The renormalization group transformation for the hierarchical O(N) spin model in four dimensions is studied by means of characteristic functions of single-site measures, and convergence of the critical trajectory to the Gaussian fixed point is shown for a sufficiently large N. In the strong coupling regime, the trajectory is controlled by the help of the exactly solved O(∞) trajectory, while, in the weak coupling regime, convergence to the Gaussian fixed point is shown by power decay of the effective coupling constant.     

Peripheral interactions of relativistic 14N nuclei with emulsion nuclei

The results of investigation of the dissociation of the 2.86-A-GeV/c ¹⁴N nucleus in an emulsion are presented. The cross sections for various fragmentation channels are given. The invariant approach to analysis of fragmentation is used. The momentum and correlation characteristics of the α particles for the ¹⁴N → 3α + X channel in the laboratory system and c.m.s. of three α particles are examined. The results obtained for the ¹⁴N nucleus are compared with similar data for the ¹²C and ¹⁶O nuclei.     

Renormalization and resummation in the O(N) model

In the O(N) model for the large N expansion one needs resummation which makes the renormalization of the model difficult. In the paper it is discussed, how can one perform a consistent perturbation theory at zero as well as at finite temperature with the help of momentum dependent renormalization schemes.     

Excitation of bands of the first negative system of the N 2 + ion in collisions of N+ and O+ ions with N2 molecules

Absolute values of the excitation cross sections of the (0,0) bands [for O⁺(⁴ S), O⁺(² P)-N₂ pairs] and the (0,0), (0,1), (1,2), and (2,3) bands [for N⁺(³ P)-N₂ pairs] of the first negative system of the N ₂ ⁺ ion have been measured in collisions with nitrogen molecules of nitrogen and oxygen ions in the ground state and in a metastable state in the interval of ion energies 1–10 keV. The process of excitation of the (0,0) band of the first negative system of the N ₂ ⁺ ion by oxygen ions in the metastable ² P state is of a quasi-resonant character. The presence in the beam of ions in metastable states was monitored by measuring the excitation efficiency of the (0,0) band λ3914 Å of the N ₂ ⁺ ion in different operating regimes of the highfrequency ion source. For N⁺ ions in the ³ P ground state, as the collision frequency is decreased the relative vibrational population of the v′=1 and v′=2 levels of the B ²Σ _u ⁺ state of the N ₂ ⁺ ion is observed to deviate strongly from the value calculated in the Franck-Condon model.     

Hyperfine interactions of 19O in TiO2 and quadrupole moments of 13,19O

The electric quadrupole interaction of ¹⁹O(I^π=(5/2)⁺, T_1/2=27.0 s) in TiO₂ single crystal was studied in detail by means of the β-NQR to determine the electric quadrupole moments Q of short-lived β-emitting nuclei ¹⁹O and ¹³O(I^π=(3/2)^-, T_1/2=8.6 ms). Two implantation sites were found for the implanted O nucleus and the quadrupole coupling constants of ¹⁹O at these sites were determined. We observed FT-NMR of the enriched stable isotope ¹⁷O in TiO₂ and obtained the electric field gradient (EFG) at the oxygen substitutional site. With this knowledge, we have determined Q(¹³O)=11.0 ± 1.3 mb and Q(¹⁹O)=3.7 ± 0.4 mb. The present results are compared with the theoretical values calculated by the shell model code, OXBASH and by the Hartree–Fock calculation with the realistic potential. This revised version was published online in August 2006 with corrections to the Cover Date.