Free Nitrogen Atom Research Articles

Evidence for two binding sites on micellization of 1-methyl-4,4'-bipyridinium reporter ion in sodium dodecyl sulfate

The chemical shifts of the title compound in sodium dodecyl sulfate (SDS) and in CD 3 OD are nearly the same and are deshielded with respect to those for a purely aqueous solution, providing evidence for a binding site associated with intercalation into a region of reduced polarity of the amphiphile. Proton relaxation times (T 1 ) in the presence of Ni(II) and SDS show that the paramagnetic ion interacts with the free nitrogen atom

Natural lifetimes of excited states of neutral nitrogen determined by time-resolved laser spectroscopy.

Radiative lifetimes were determined for three quartet states of neutral nitrogen, and sequences of Rydberg states were studied using depletion spectroscopy. Free nitrogen atoms were generated by photodissociation of ${\mathrm{N}}_{2}$O using frequency-tripled dye-laser radiation that was two-photon resonant with the 2${\mathit{p}}^{2}$3p $^{4}$S or $^{4}$D states. Further quartet states were reached by a subsequent single-photon absorption. We obtain \ensuremath{\tau}(2${\mathit{p}}^{2}$3p $^{4}$${\mathit{D}}_{7/2}$)=44(2) ns, \ensuremath{\tau}(2${\mathit{p}}^{2}$3p $^{4}$${\mathit{S}}_{3/2}$)=26.0(1.5) ns, and \ensuremath{\tau}(2${\mathit{p}}^{2}$6${\mathit{s}}^{4}$${\mathit{P}}_{5/2}$)=41(7) ns.

Structure of a methylmercury complex with 4-nitroimidazole

(4-Nitroimidazolato)methylmercury(II) belongs to the rhombohedral space group R3 c, with a=11.434 Å, α=111.40 o and Z=6. The structure was refined on 558 unique non-zero reflections to R=0.037. The CH 3Hg + group is linearly bonded to the heterocyclic nitrogen atom more remote from the nitro substituent. The metal forms secondary bonds in its equatorial plane with available donor atoms in adjacent molecules: (2 + 3) coordination around Hg is completed by contacts with a nitro oxygen and the free nitrogen atom of one molecule, and another nitro oxygen in a different molecule. Six molecules are linked into a closed loop around the three-fold axis by means of these secondary bonds.

ESR and a b i n i t i o theoretical studies of the cation radicals 14N+4 and 15N+4: The trapping of ion–neutral reaction products in neon matrices at 4 K

The 14N+4 and 15N+4 molecular cation radicals have been generated by the ion–neutral reaction N+2 +N2 and isolated in solid neon matrices at 4 K for detailed ESR (electron spin resonance) investigation. Both photonionization at 16.8 eV and electron bombardment (50 eV) were used in conjunction with the neon matrix trapping technique to produce the N+4 dimer cation. The ESR results clearly show that N+4 is linear and has a 2Σμ ground electronic state. The magnetic parameters in neon are: g∥=2.0016(4) and g⊥=1.9998(2); A∥(14N)=311(1) MHz and A⊥(14N)=264(1) MHz for the central atoms and ‖A∥‖=10.4(5) MHz and ‖A⊥‖=20.4(1) MHz for the outer or terminal 14N atoms. Electronic structure information for N+4 was obtained from the ESR results and compared with ab initio CI calculations. The unpaired electron resides primarily on the inner nitrogen atoms with significant 2pσ and 2s character. Orbital characters obtained from the commonly applied free atom comparison method (FACM) were compared with the results of a Mulliken type spin population analysis conducted on the calculated wave function. The calculated nuclear hyperfine parameters (A tensors) showed reasonable agreement with experiment except for the very small Aiso parameter for the outer nitrogen atoms. Benchmark calculations employing large basis sets were conducted for the free nitrogen atom; these efforts demonstrate the difficulty in computing the Aiso parameter when inner shell effects are important.

高張力鋼溶接熱影響部の動的ひずみ時効による延性低下

When tensile tests on mild steel are carried out at various temperatures, the serrated yielding and flow are observed at a certain testing temperature range, specially 100-300°C, and the consequent em-brittlement occurs. This phenomenon is generally known as a blue brittleness or a dynamic strain aging and is related to testing temperature, solute atom contents (carbon and/or nitrogen contents), strain rate and so forth.On the other hand, for base metal of QT-type high strength low alloy steels in which solute atoms such as carbon and nitrogen are fixed as carbide, nitride or carbo-nitride by heat treatment, such embrit-tlement seems to be not apt to occur comparatively. But, even if QT-type steels, there is a possibility of dynamic strain aging in heat-affected zone (HAZ) because of the above carbide, nitride or carbo-nitride dissolving by welding heats, and the consequent embrittlernent.This study was investigated about the ductility loss due to dynamic strain aging in HAZ of a 80 kg/mm2 class high strength low alloy steel.It is found by this study that dynamic strain aging and, thus, the ductility loss can occur in HAZ even if QT-type steels. The degree of ductility loss is increased in the order of upper bainite, lower bainite and martensite structure.These results can be qualitatively interpreted by considering as interaction between dislocations and solute atoms, specifically nitrogen atoms rather than carbon atoms.Transformed HAZ, which is heated above 1200°C and has martensite structure and, thus, a high content of free nitrogen atoms, is sensitive to ductility loss due to dynamic strain aging as well as the deterioration of grain coarsened HAZ toughness.

Cryptands as bases in proton-transfer reactions. The rates and hydrogen isotope effects in the ionization of ethyl nitroacetate by cryptands

The rates and kinetic hydrogen isotope effects for the proton-transfer reaction between ethyl nitroacetate and three cryptands in the free base and monoprotonated forms have been measured. The catalytic constants for the free bases are ca. 1 order of magnitude smaller, and those of the monoprotonated cryptands ca. 2 orders of magnitude smaller, than those of ‘normal’ bases of comparable basicity. Two possible explanations for the slow rates are discussed: sterically hindered direct transfer of the proton to within the cavity of the ligand, and the reaction of a small, but kinetically active, fraction of molecules containing the free nitrogen atom in an exo-conformation. It is argued that the catalytic activity of the unprotonated cryptands is mainly due to the direct transfer of the proton to the cavity, but it is difficult to decide between the two possibilities for the monoprotonated cryptands. The observed kinetic hydrogen isotope effects were 7.2 for the unprotonated cryptand and in the range 8–8.5 for the monoprotonated cryptands.

Laserspektroskopische Untersuchungen an nicht-stabilisierten N2(B3IIg, ν; = 13)-Molekülen / Laser Spectroscopic Studies on Non-stabilized N2(B3IIg, ν; = 13) molecules

Unstabilized N2(B3IIg, ν = 13) quasi-molecules were analysed by excitation with a tunable dye-laser into the N2(C3IIu) state and observation of the following fluorescence to N2(B3IIg, ν) levels. The quasi-molecules are in equilibrium with the free nitrogen atoms. The detection limit of this technique is 105 molecules/cm3. By the same method, a rotational analysis of molecules stabilized into (B3IIg, ν ≦ 12) levels by three-body recombination processes was achieved with a resolution better than that reached by emission spectroscopy of the Lewis-Rayleigh afterglow

Detection of nitrogen atoms by means of thin silver films

Experimental results concerning the interaction of atomic nitrogen with the surface of thin silver films and its influence of the electrical resistance of the films are reported, which show that even small amounts of free nitrogen atoms in molecular nitrogen bring about fractional resistance increases of several tens of percentages. The effect is partly reversible; desorption may occur either by the action of molecular nitrogen or on evacuation of the reaction vessel. In the region of reversibility of the δ R versus time curve, the initial slope of the curve can be taken as a measure of the amount of nitrogen atoms present in the reaction vessel.

The infrared spectra of caffeine salts

The infrared spectra of caffeine and its salts show that protonation occurs at position 9, the free nitrogen atom in the imidazole ring. N+H stretching and in-plane and out-of-plane bending modes have been assigned with the help of the deuterated salts. Protonation causes changes in some ring modes, accompanied by shifts in the carbonyl stretching frequencies to higher values.

The infrared spectra of theobromine salts

From the infrared spectra of theobromine salts it is concluded that the salts are probably arranged in hydrogen-bonded centrosymmetric pairs involving [Formula: see text] interactions. [Formula: see text] anion− hydrogen bonds are formed by protonation of the free nitrogen atom (N9) in the imidazole ring. Infrared absorption bands arising from the former hydrogen bond constantly appear near 3 000 cm−1, whereas those from the latter shift from 2 580 to 3 300 cm−1, depending on the anion. In-plane NH and N+H deformation modes give bands near 1 485 and 1 160 cm−1, respectively. Out-of-plane NH modes have been located, but precise assignments are not possible.The assignments for some other bands which show deuteration shifts are detailed, and the carbonyl stretching vibrations which increase in frequency on protonation of the free base are identified.

Additional Observations of Chemiluminescence in Mixtures of Atomic Oxygen and Nitrogen

Reinvestigation of the nitrogen afterglow using specially purified nitrogen indicates that an intermediary or precursor in the reaction path leading from free nitrogen atoms to the emission state is quenched by N2 but not by He. The O2 atmospheric bands and the O I 5577-Å line were not detected at the NO null titration point. The O2 Herzberg bands are independent of pressure in both N2 and 1% N2 in He systems, indicating that equilibrium exists between the radiative state and free atomic oxygen.

遊離酸素原子および窒素原子再結合反応に対する遷移金属の触媒能の比較

遊離酸素原子および窒素原子再結合反応に対する遷移金属の触媒能の比較

Thermometric Study of the Frozen Products from the Nitrogen Microwave Discharge

Thermometric observations have been made of the phenomena accompanying the stabilization and the recombination of free nitrogen atoms in a solid molecular nitrogen matrix at liquid helium temperatures. Condensation from the gas phase may occur at temperatures considerably above the 4.2°K coolant temperature as the result of the normal change in heat content and the heat of atom recombination. Estimates, made from the latter effects, of the free atom concentration in the gas phase were as high as 4 atom %. Qualitative confirmation of the presence of an energetic species stabilized in the solid phase was made by detection of heat release upon warmup. From the latter effect a minimum nitrogen atom concentration in the solid of 0.03 atom % was estimated. For the conditions used the initiation of atom recombination occurs at a temperature of about 9°K. The upper limit of about 36°K for stabilization coincides with the known thermal transition in solid nitrogen. The data suggest that at least above 9°K diffusion of nitrogen atoms occurs throughout the solid matrix during deposition from the gas phase. If recombination during warmup is diffusion-controlled, unusual dependence upon temperature is indicated.

The Binding Energy of Nitrogen in a Dislocation

The solubility of interstitially dissolved nitrogen has been measured both in annealed and in cold-worked alpha iron by the internal friction technique in more detail than in the original work of Dijkstra. The dissolved nitrogen in annealed material, in equilibrium with a precipitated nitride, has a heat of solution of 0 26 eV per nitrogen atom. This agrees reasonably well with other published values. A new approach has been introduced into the treatment of the results for the solubility of nitrogen in cold-worked iron. Equilibrium is considered between nitrogen atoms in free solution and nitrogen atoms bound in dislocation sites. Since the number of dislocation sites is fixed, account is taken of the proportion of these occupied at different temperatures. The value for the binding energy of nitrogen atoms in dislocation sites is estimated as lying between 0 75 and 0.8 eV per nitrogen atom.

The Binding Energy of Nitrogen in a Dislocation

The solubility of interstitially dissolved nitrogen has been measured both in annealed and in cold-worked alpha iron by the internal friction technique in more detail than in the original work of Dijkstra. The dissolved nitrogen in annealed material, in equilibrium with a precipitated nitride, has a heat of solution of 0 26 eV per nitrogen atom. This agrees reasonably well with other published values. A new approach has been introduced into the treatment of the results for the solubility of nitrogen in cold-worked iron. Equilibrium is considered between nitrogen atoms in free solution and nitrogen atoms bound in dislocation sites. Since the number of dislocation sites is fixed, account is taken of the proportion of these occupied at different temperatures. The value for the binding energy of nitrogen atoms in dislocation sites is estimated as lying between 0 75 and 0.8 eV per nitrogen atom.