Molecular beam chemiluminescence XI: kinetic and internal energy dependence of the NO + O3 → NO2*,→ NO23 reaction

Seeded supersonic NO beams were used to study the kinetic energy dependence of both the electronic (NO₂^*) and vibrational (NO₂³) chemiluminescence of the NO + O₃ reaction. In addition the electronic CL is found to be enhanced by raising the NO internal temperature. This is shown to be due to enhanced reactivity of the NO(²Π,_{$\text{3}\text{2}$}) fine structure component. By difference NO(²Π_{$\text{1}\text{2}$}) is concluded to yield predominantly groundstate NO₂³. The excitation function for NO₂^* formation from NO(²Π_{$\text{3}\text{2}$}) is of the form σ_{$\text{3}\text{2}$}(E) = C(E/E₀ - 1)ⁿ over the 3–6 kcal energy range where n = 2.4 ± 0.15, C = 0.163 Ų and E₀ = 3.2 ± 0.3 kcal/mole. Vibrational IR emission from NO₂³ has an energy dependence different from electronic NO₂^* emission, confirming that emitters are formed predominantly in distinct reaction channels rather than via a common precursor (either NO₂^* or NO₂³). The short wavelength cutoff of the CL spectra recorded at elevated collision energies E ? 15 kcal/mole corresponds to the total available energy. These and literature results are discussed in the light of general properties of the (generally unknown) ONO₃ potential energy surfaces. The formation of electronically excited NO₂^* rather than energetically preferred O₂ (¹ Δg) (Gauthier and Snelling) can be rationalized in terms of surface hopping near a known intersection of potential energy surfaces more easily than by vibronic interaction in the asymptotic NO₂ product.     

Bestimmung von NO2? und NO3? in Lebensmitteln mit Hilfe chromatographischer Methoden

Zusammenfassung WÄhrend NO ₂ ^– problemlos nach dem Griess-Verfahren bestimmt werden kann, treten bei der spektralphotometrischen Erfassung von NO ₃ ^– hÄufig Störungen auf.Zum Nachweis geringer NO ₃ ^– -Mengen eignet sich die Nitrierung von p-Kresol zu 4-Methyl-2-nitrophenol, das durch Wasserdampfdestillation aus dem Reaktionsgemisch abgetrennt und nach überführung in Toluol durch HPLC bzw. GC bestimmt wird.Zur schnellen Erfassung von NO ₂ ^– neben NO ₃ ^– kann neben der Ionen-Chromatographie an AnionenaustauschersÄulen vorteilhaft die Ionen-Paar-Chromatographie an RPSÄulen eingesetzt werden. Durch parallele Anwendung verschiedener Methoden gelingt es, NO ₂ ^– - und NO ₃ ^– -Gehalte auch von komplex zusammengesetzten Lebensmitteln über einen weiten Konzentrationsbereich mit gro\er Genauigkeit störungsfrei zu ermitteln.

---

Determination of NO ₂ ^– and NO ₃ ^– in foods by chromatography

Summary The determination of NO ₂ ^– is achieved by the Griess procedure without problems, whereas during the analysis of NO ₃ ^– by spectrophotometric methods disturbances often occur.Small amounts of NO ₃ ^– are detectable after nitration of p-cresol, subsequent separation of 4-methyl-2-nitrophenol by steam distillation and its determination by HPLC or GLC after extraction with toluene. To enable a rapid determination of NO ₂ ^– as well NO ₃ ^– , apart from the ionchromatographic method with anion-exchange columns the comparatively equal ion-pair chromatographic system using RP columns may also be used. By the parallel use of different methods it is possible to determine the NO ₂ ^– and NO ₃ ^– contents, even in complex matrices, over a wide concentration range with a large degree of accuracy and a minimum of disturbances.

---

---

Nach einem Vortrag anlÄ\lich des Deutschen Lebensmittelchemikertages, München 1983     

Double electron transfer reactions of CO22+ ions

Time-of-flight techniques have been used to measure fast neutral CO₂ products from double electron transfer reactions of CO₂²⁺ ions with 4.0–7.0 keV impact energies. Double electron transfer cross sections have been determined to be in the range of (1.1–12.5) × 10^?16 cm² for reactions of CO₂²⁺ ions with CO₂, CO, N₂, Ar and O₂.     

Predissociation of the C2Σu+ state of N2+

Two mechanisms for the predissociation of the C²Σ_u⁺ state of N₂⁺ are discussed - the accidental mechanism and a direct, homogeneous process C → B²Σ_u⁺. The matrix elements for the latter channel are dominated by a contribution from the nuclear kinetic energy operator, containing a Franck-Condon integral of form 〈?|?/?R|υ′〉.     

The electronic structure of N4O62+ and the bonding interaction of NO+ and NO3−

The results are reported of an MO-SCF-CNDO/2 study of the experimental and optimal geometries of the N₄O₆²⁺ion cluster. The calculations are shown to support the stable existence of the N₄O₆²⁺ complex and the suggestion of its discoverers [1] on the role of NO⁺ in the N₂O₄ solutions. The proposed interpretation of the bonding interaction explains why the shortest N β O distances are found with the NO⁺ ions which have their nitrogen atoms displaced out of the NO₃^? plane.     

Chemiluminescence and auto-oscillations in the (S?Cr2O72+?UO22+) system

Quasi-harmonic oscillations of chemiluminescence intensity at certain concentrations of the components for the (S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) system in concentrated sulfuric acid and chemiluminescence and dark stages with the participation of intermediates Cr(V), U(IV) and sulfur peroxide radicals (HS₂O₆ ^.) have been discovered. Chemiluminescence is attributed to the interaction of HS₂O₆ ^. compounds. The processes of deactivation of the excited states of uranyl involve the participation of Cr(V). A scheme for the oscillation chemiluminescence reactions is suggested.

---

(S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) H₂SO₄ , . Cr(V), U(IV) (HS₂O₆ ^.) HS₂O₆ ^. Cr(V) . .

     

Theoretical study of the 2Σu+ and 2Σg+ states of Li2− and Na2−

Ab initio calculations are performed to obtain potential energy curves for the X¹Σ_g⁺ state of Li₂ and Na₂ and the X²Σ_g⁺ and A²Σ_g⁺ states of their anions. The A²Σ_g⁺ M₂^? curves are found to intersect the X¹Σ_g⁺M₂ curves at low energies and are expected to play a major role in the e^? + M₂ → M^? + M process.     

Photodissociation of O2+(H2O)

The photodissociation cross section of the weakly bound positive ion cluster O₂⁺(H₂O) has been measured at 15 discrete energies between 1.833 and 2.727 eV. Measurements indicate the cross section increases smoothly from 0.6 to 6 × 10^-18 cm² over this energy range. These cross section values are the largest reported for a positive ion cluster of atmospheric importance.     

The vinyloxonium cation (CH2CHOH2+)

Ab initio Molecular orbital calculations with large basis sets and incorporating correlation are used to examine the structures and relative energies of the vinyloxonium (CH₂CHOH₂⁺) and 1-hydroxyethyl (CH₃CHOH⁺) cations. The best structure of the vinyloxonium ion has the OH₂ plane perpendicular to the CCO plane. The energy difference between the vinyloxonium and 1-hydroxyethyl cations is predicted to be 92 kJ mol^?1, substantially greater than a recent experimental estimate of 41 ± 12 kJ mol^?1     

Die polarographische reduktion von NO3− in gegenwart von CrO42−

It has been observed, that on the d.c. polarograms of nitrate, even at the very small concentration of CrO₄^2? (of the order 10^?7 mol dm^?3) a maximum appears at the potential ?1.7 V. The maximum is of catalytic nature and may be used for analytical purposes.     

Wavelength-resolved fluorescence lifetimes of gas-phase ions: CO2+ and CS2+

A method is described for measuring wavelength-resolved fluorescence lifetimes of ions formed by HeIα photoionization, using electric-field drift of the ions in competition with fluorescence. Fluorescence lifetimes of 216 and 232 ns for the 357 nm and 378 nm peaks of N₂O⁺, and 3.5 μs for the à → X? band of CS₂⁺, were measured. The wavelength-resolved à → X? band of CO₂⁺ showed no significant dependence of fluorescence lifetime on V′, but there is some indication of variation in the CS₂⁺ lifetimes in the à → X? band.     

Kinetic energy dependence of the reactions of N+ and N2+ with molybdenum

Mass-selected beams of N⁺ and N₂⁺ in the energy range 5–50 eV react with molybdenum to produce a surface nitride. The relative reaction cross section for N⁺ reaction is higher than that of N₂⁺ in the range 5–25 eV and N₂⁺ exhibits a reaction threshold near 7 eV. The N₂⁺ threshold suggests collisional dissociation prior to reaction.     

On the structure and photodissociation of cluster ions in the gas phase. (N2) (O2+) and (NO)2+

Results are presented for two experiments on N₂O₂⁺ cluster ions formed via the reactions O₂⁺ + N₂ + M → (N₂) (O₂⁺) + M (i), and NO⁺ + NO + M → (NO)₂⁺ + M (ii). In the first experiment the N₂O₂⁺ clusters are collisionally dissociated. The resulting collision-induced dissociation (CID) spectra show almost exclusively O₂⁺ and N₂⁺ products from N₂ O₂⁺ formed via the first reaction, and almost exclusively NO⁺ products from N₂O₂⁺ formed via the second reaction. In the second experiment, single-photon photodissociation of N₂O₂⁺ ions produced by both reactions (i) and (ii) was investigate using 514.5 and 634 nm radiation. The results indicate that the N₂O₂⁺ cluster from reaction (i) cannot be photodissociated while the N₂O₂⁺ cluster from reaction (ii) undergoes photodissociation at both wavelengths. These experiments indicate that two distinct N₂O₂⁺ cluster ions exist and that reactions (i) and (ii) selectively produce the two ions.     

Ionen-chromatographische Bestimmung der Anionen Cl?, NO3? und SO42? in Regenwasser

Zusammenfassung Der Säureeintrag mit der Naßdeposition auf die Vegetationsdecke und die Gewässer ist für die Beurteilung vieler Umweltschäden von wachsender Bedeutung.Es wird über die Ionen-Chromatographie als Analyseverfahren der wichtigsten im Regen enthaltenen Anionen berichtet. Diese Anionen fungieren teilweise als anionische Komponenten der für den Säuregrad des Regens verantwortlichen starken vollständig dissoziierten Säuren H₂SO₄, HNO₃ und in geringerem Ausmaß auch HCl. Als vorteilhaft haben sich die ausreichende Empfindlichkeit der Ionen-Chromatographie, ihre Automatisierung, die Möglichkeit zur simultanen Bestimmung der drei Anionen, das kleine Probenvolumen und die Möglichkeit der direkten Injektion der Probe ohne weitere Vorbereitung erwiesen. Die häufigsten Fehlerquellen bei der Bestimmung der Anionen liegen in der Probennahme, der Probenlagerung sowie in der unzulänglichen Reinigung der Regensammlerteile und der Aufbewahrungsgefäße.Als praktisches Anwendungsbeispiel werden ionen-chromatographisch bestimmte Anionenkonzentrationen in Regenproben aus dem Jahre 1983 vorgestellt und diskutiert. Die Probennahme erfolgte an vier Sammelstellen im Raum Stolberg-Jülich: Jülich-Hambach, Stolberg-Werth, Stolberg-Gressenich bzw. Stolberg-Münsterbusch und Stolberg-Binsfeldhammer. Die Anionenkonzentrationen variierten zwischen 0,2–7 mg/l Cl^–, 0,5–10 mg/l NO ₃ ^– und 2–10 mg/l SO ₄ ^2– . Die maximale Standardabweichung betrug 15%.

---

Ion-chromatographic determination of the anions Cl^–, NO ₃ ^– and SO ₄ ^2– in rain water

Summary Wet deposition of acid onto the vegetation blanket and the surface of fresh waters is of increasing importance for the estimation of environmental damages.Ion-chromatography has been evaluated as a suitable tool for the determination of the most important anions present in rain water. These anions are partly present as anionic components of the totally dissociated strong acids H₂SO₄, HNO₃, and HCl responsible for the acidity of the rain. The advantages of the method are sufficient sensitivity, automation, the possibility of a direct simultaneous determination of the three anions and small sample volume. The most frequent sources of error can occur in the sampling step, during sample storage and due to insufficient cleaning of the sampling bottles and the components of the rain water sampler.As a practical application of ion-chromatography the concentrations of the three most important anions were determined in rain water samples taken in 1983. Sampling was performed at four sampling sites of the Stolberg-Juelich region: Juelich-Hambach, Stolberg-Werth, Stolberg-Gressenich or Stolberg-Muensterbusch und Stolberg-Binsfeldhammer. The anion concentrations varied in the ranges 0.2–7 mg/l Cl^–, 0.5–10 mg/l NO ₃ ^– and 2–20 mg/l SO ₄ ^2– and had a standard deviation up to 15%.

---

---

Auszugsweise vorgetragen beim Symposium Anorganische Anionenanalytik, Regensburg, 19.–21. 9. 1984

---

Entnommen aus der Dissertation von Dipl.-Phys. F. Wagner, RWTH Aachen 1985     

Determination of Cl?, NO3? and SO42? in Pore waters of sediments

Summary It is shown that ion chromatography can be successfully employed for the determination of Cl^–, NO ₃ ^– , and SO ₄ ^2– in pore waters of sediment cores. Using three examples of different sediment cores from the Elbe river estuary the application and the relevance of the results are demonstrated.

---

Bestimmung von Cl^–, NO ₃ ^– und SO ₄ ^2– in Sediment-Porenwässern

Zusammenfassung Es wird gezeigt, daß die Analyse von Cl^–, NO ₃ ^– und SO ₄ ^2– in Porenwässern von Sedimentkernen mit Vorteil durch ein ionenchromatographisches Verfahren durchgeführt werden kann. An drei Beispielen von Sedimentkernen aus unterschiedlichen Bereichen des Elbeaestuars wird die Einsatzmöglichkeit und die Aussagekraft der Methode demonstriert.

---

---

Lecture given at the Symposium on Inorganic Anion Analysis, Regensburg, 19.–21.9. 1984     

Interpretation of energy stability for Ti27+ and Ti26+ dimers

By using the interacting bonds method (IBM), it has been established that for the chloride Ziegler systems (TiCl₄+AlR₃) for polymerization the formation of Ti ₂ ⁷⁺ and Ti ₂ ⁶⁺ pairs is a thermodynamically favorable process.

---

(TiCl₄+AlR₃) () , Ti ₂ ⁷⁺ Ti ₂ ⁶⁺ .

     

Further studies of the N2+ + N2 → N4+ association reaction

Data are presented which strongly suggest that stabilisation of the excited intermediate (N₄⁺)* complex in the reaction (1) N₂⁺ + 2N₂ (rate coefficient k₁) occurs via N₂ switching whereas for (2) N₂⁺ + N₂ + He (rate coefficient k₂) it occurs via superelastic He collisions. This explains the differing temperature variations of k₁ and k₂ previously obtained for these reactions. Drift tube data are also presented which show how k₁ varies with N₂⁺/N₂ centre-of-mass energy as compared with thermal energy.     

Coincidence studies of fluorescence and dissociation processes in electronic excited states of I2+, Br2+, IBr+ and ICl+

The PIFCO technique in which mass-selected photoion—fluorescence photon coincidences are counted, was used to investigate whether I₂⁺, IBr⁺ and ICl⁺ fluoresce. Measurements were made of lifetimes and fluorescence quantum yields of electronic excited states of these ions. Emission was discovered for I₂⁺ and IBr⁺, but ICl⁺ apparently does not fluoresce. Information on the radiative properties of Br₂⁺ was obtained as a by-product of the work on IBr⁺. Fragment ion kinetic energy releases were determined and provide information on dissociative ionization processes in the halogen and interhalogen ions studied.     

Low-lying states of cs22+

Using an MC SCF CI method, wavefunctions for the ground state ¹∑⁺_g and the excited states of the symmetries ¹∑⁺_g, ¹Π_g, and ¹Δ_g of the Cs²⁺₂ ionic system are generated. The potential curves for eleven ¹∑⁺_g twelve ¹Π_g, and six ¹Δ_g states are calculated. Results suggest a small charge-transfer cross section for the reaction CS⁺ + Cs⁺ → Cs CS²⁺.