Photoelectron spectra of quaternary salts in solution

The ionisation energies, measured by He(I) photoelectron spectroscopy, are reported for I^?, Cl^?, Br^?, CNS^? and NO^?₂ in adiponitrile solution. These energies give a straight line when plotted against the energies of the electron transfer to solvent absorption bands of the ions in acetonitrile solution. The intercept gives the electron affinity of the solvent; for acetonitrile, assumed to be spectroscopically equivalent to adiponitrile, the electron affinity is found to be 1.85 eV; for water it is 1.65 eV. The energies of electron transfers not observable in the UV absorption spectrum of NO^?₂ solutions are estimated from the photoelectron spectra.     

Raman and Photoluminescence Spectroscopic Detection of Surface‐Bound Li+O2− Defect Sites in Li‐Doped ZnO Nanocrystals Derived from Molecular Precursors

We present a detailed study of Raman spectroscopy and photoluminescence measurements on Li‐doped ZnO nanocrystals with varying lithium concentrations. The samples were prepared starting from molecular precursors at low temperature. The Raman spectra revealed several sharp lines in the range of 100–200 cm^?1, which are attributed to acoustical phonons. In the high‐energy range two peaks were observed at 735 cm^?1 and 1090 cm^?1. Excitation‐dependent Raman spectroscopy of the 1090 cm^?1 mode revealed resonance enhancement at excitation energies around 2.2 eV. This energy coincides with an emission band in the photoluminescence spectra. The emission is attributed to the deep lithium acceptor and intrinsic point defects such as oxygen vacancies. Based on the combined Raman and PL results, we introduce a model of surface‐bound LiO₂ defect sites, that is, the presence of Li⁺O₂^? superoxide. Accordingly, the observed Raman peaks at 735 cm^?1 and 1090 cm^?1 are assigned to Li? O and O? O vibrations of LiO₂.     

Ion-molecule reactions observed for nitroaromatic compounds in negative ion fast atom bombardment mass spectrometry

Analyses of a series of nitroaromatic compounds using fast atom bombardment (FAB) mass spectrometry are discussed. An interesting ion-molecule reaction leading to [M + O ? H]^? ions is observed in the negative ion FAB spectra. Evidence from linked-scan and collision-induced dissociation spectra proved that [M + O ? H]^? ions are produced by the following reaction: M + NO₂^? → [M + NO₂]^? → [M + O ? H]^?. These experiments also showed that M^?˙ ions are produced in part by the exchange of an electron between M and NO₂^? species. All samples showed M^?˙, [M ? H]^? or both ions in their negative ion FAB spectra. Not all analytes studied showed either [M + H]⁺ and/or M⁺˙ in the positive ion FAB spectra. No M⁺˙ ions were observed for ions having ionization energies above ～9 eV.     

SCF-Xα MO studies of the x-ray spectra of CuO and ZnO

SCF-Xα scattered wave cluster MO calculations for the oxyanions CuO^?6₄ (D_4h symmetry) and ZnO^?6₄ (Td symmetry) yield results in good agreement with the X-ray photoelectron and X-ray emission spectra of CuO and ZnO, respectively. Agreement of the calculations with optical data is fair. Calculations of the valence electron and core electron hole states of these oxyanions support the assignment of photoelectron shakeup satellites to valence band to conduction band transitions. Calculated shakeup energies for the Cu2p core spectrum in CuO are 7.4 and 9.9 eV (cf. experimental values of 7.5 and 10.0 eV) while shakeup peaks in the valence region spectrum are predicted at 6.1 and 8.0 eV. (Cf. a broad peak with maximum at 8.1 eV observed experimentally.) The absence of intense low energy satellites in the spectra of ZnO is explained by the small amount of electron reorganization in the outer valence levels attendant upon hole formation.     

Reaction dynamics of the dichlorocarbene anion using tandem mass spectrometry

The dissociation dynamics of CCl₂^? anions were studied under various internal energy conditions. This study involved the measurement of daughter-ion spectra and branching ratios and of the amount of kinetic energy released (KER) on the fragments. The competition between C and Cl loss for CCl₂^? ions created by any of the following sequence of processes: (1) was particularly investigated. For process (1), the amount of fragmenting CCl₂^? ions is 8–10 times larger with Kr than with Xe or C₆H₆. The KER for Cl loss is smaller than 0.20 eV with the three target gases used. For the loss of C, the KER is much larger (0.7 eV). This KER is, however, equal to 0.21 eV for the collisionally activated C loss in process (2). For this latter process, the C loss vs. Cl loss branching ratio decreases with increasing internal energy. The KERs measured for process (3) are very similar to those obtained for process (1). It is suggested that repulsive or slightly bound excited states which correlate directly to the Cl₂^? (X²Σ_u⁺) + C asymptote and which are vibronically coupled to the ground state play an important role in these dissociation processes.     

Photodetachment of NO−2; experimental evidence for a new isomer

The relative cross section for the gas phase photodetachment of electrons has been determined for nitrite ions in the wavelength region 280–740 nm (4.43-1.68 eV). The vertical detachment energy for ONO^? has been determined to be ≈ 2.8 eV. Evidence is presented for a new isomer of NO^?₂.     

Energy and angular differential cross sections for K + NO2 charge transfer reactions

Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO^?₂ in its ground ¹A₁ and excited ³B₁ state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO^?₂.     

Total ionization and electron attachment cross sections of CCl2F2 by electron impact

The absolute total ionization cross sections from threshold to 250 eV and dissociative attachment cross sections from zero to 10 eV have been measured for the CCl₂F₂ (dichloro-difluoro-methane) molecule by using a parallel plate condenser type ionization chamber. The maximum of the ionization cross-section curve was found to be at an energy of about 90 eV with a cross section of 1.44 × 10^?19 m². The attachment cross-section curve shows three peaks, the most intense being at zero electron energy with a cross-section value of 1.80 × 10^?20 m², and the other two at energies of 0.6 eV and 3.5 eV, respectively. The maximal relative error in cross-section values is 0.08, for electron energies larger than 0.4 eV.     

Photoelectron spectroscopy of (CO2)n(H2O) m − clusters

Photoelectron spectra of (CO₂)_nH₂O^? (2≤n≤8) and (CO₂)_n(H₂O) ₂ ^? (1≤n≤2) were measured at the photon energy of 3.49 eV. The spectra show unresolved broad features, which are approximated by Gaussians. The vertical detachment energies (VDEs) were determined as a function of the cluster size. For (CO₂)_nH₂O^?, the VDE-n plots exhibit a sharp discontinuity between n=3 and 4; the VDE value is ≈3.5 eV at n=3, while it drops down abruptly to 2.59 eV at n=4. This discontinuity in VDE is ascribed to "core switching" at n=4; a C₂O ₄ ^? dimer anion forms the core of (CO₂)_nH₂O^? for n≤3, while a monomer CO ₂ ^? is the core for n≥4. The (CO₂)₂(H₂O) ₂ ^? ion has a VDE of 2.33 eV, indicating the presence of a CO ₂ ^? monomer core in the binary clusters containing two H₂O molecules.     

X-ray photoelectron spectroscopic study of the interaction of supported metal catalysts with NO<Subscript>x</Subscript>

The reactions of the platinum and rhodium model catalysts applied to aluminum oxide with NO_x (10 Torr NO + 10 Torr O₂) were studied by X-ray photoelectron spectroscopy. The reaction conducted at room temperature formed on the surface of the oxide support the NO _3,s ^? nitrate ions characterized by the N1s line at 407.4 eV and O1s line at 533.1 eV and the NO _2,s ^? nitrite ions characterized by the N1s line with a binding energy of 404.7 eV. At the same time, the Pt4f and Rh3d lines of the supported platinum particles are shifted toward higher binding energies by 0.5–1.0 eV and 0.7–1.2 eV, respectively. It is assumed that the binding energies increase due to changes in the chemical state of the platinum metal in which oxygen is dissolved. The reaction of NO_x with Pt/Al₂O₃ at 200°C forms platinum oxide defined by the Pt4f _7/2 line with a binding energy of 72.3 eV.     

In situ dielectric measurements of Zn–Al layered double hydroxide with anionic nitrate ions

Zn–Al–NO₃–layered double hydroxide (Zn–Al–NO₃–LDH) was prepared by the co-precipitation method with a ratio of Zn/Al = 4 and at a constant pH of 7. Powder XRD patterns showed the characteristic peaks of layered structure of the LDH sample. Thermogravimetric analysis (TGA) and infrared spectra of the sample were investigated. Because of the existence of water molecules and anionic NO₃⁻ in the interlayer of the LDH, the in situ dielectric spectroscopy of the LDH can be described by an anomalous low frequency dispersion using the second type of Universal Power Law. Novel measurements of activation energy of LDH have been obtained at five different frequencies. The energy value increased from 0.05 eV at 1 MHz to 0.37 eV at 134 Hz. The conductivity spectra of sample were studied as a function in temperature of the in situ measurements. The ionic conductivity (dc) of LDH increased as the in situ temperature increased.     

Differential cross section for CN− formation from dissociative electron attachment to the cyanogen molecule C2N2

The differential cross section for CN^? formaition from dissoiiativc attachment on C₂N₂ has been obtained in a crossed-beam experiment. Below 10 eV incident electron energy thc CN^? cross section shows two broad overlapping peaks with maxima at 5.4 and 7.3 eV corresponding to the formation of CN^? in its ground electronic state ¹σ⁺ plus the CN radical in the first excited state²π and the ground stale ²Σ+ respcctively     

State-to-state total cross sections for ion-pair formation

Relative total cross sections are reported for the production of electrons and anions in collisions between an alkali atom (Na, K, Cs) and the molecules O₂ and NO. The formation of electrons is due to autoionization of vibrationally excited O₂^? (gu′ ? 4) respectively NO^? (υ′ ? 1) molecules. The experiments have been performed with fast alkali atom beams in the laboratory energy range of 30–300 eV.     

Collisional ionization of fast K atoms by H2S and D2S

The process K + H₂S/D₂S → HS^?/DS^? + K⁺+ H/D has been investigated for K impact energies from near threshold to ≈100 eV. Positive and negative ion energy spectra have been obtained in the forward direction. The threshold for HS^? or DS^?production corresponds to the HS^?/DS^?+ H/D limit of the ²A₁ H₂S^?/D₂S^? state at 1.55 eV.     

Photoconduction in poly(ethylene terephthalate). I. Mechanisms of carrier generation

Mechanisms of photocarrier generation in poly(ethylene terephthalate) (PET) have been investigated. In the wavelength range of λ ≦320 nm, the photocurrent spectra correspond closely with the optical absorption spectra of PET and the assignment of the absorption peaks revealed that photocarriers are generated through ππ^* excitations. In the wavelength range from 320 to 400 nm, photocarriers are injected from metal electrodes. The threshold energies for Al and Cu electrodes are 2.8₇ and 2.9₄ eV, respectively, indicating the presence of surface states. The simplified model gives the density of the surface states as 1.7 × 10¹⁴ cm^?2 eV^?1.     

2s and 2p X-ray photoelectron spectra of Ti4+ ion in TiO2

A detailed experimental study of the 2s- and 2p XPS spectra of TiO₂ revealed new (charge-transfer) shake-up satellite structures (at 4.0–5.0 eV from the main peaks) which can be explained using molecular orbital representation. The satellite peaks, situated at about 26 eV from the main peaks, the origin of which was in doubt in the previously reported works are shown conclusively in the present investigation to be energy loss peaks. The relative energies and intensities of the observed satellites are presented and the theoretical implications of the work are discussed.     

Selective “naked-eye” sensing of acetate ion based on conformational flexible amide-pyridinium receptor

A simple pincer-shape anion receptor L1 containing amide-pyridinium as binding unit was synthesized and its anion binding properties were investigated by UV–Vis, NMR titration spectra and molecular simulation. L1 displayed better affinity toward AcO^? ion with visible color change compared with other investigated anions, including F^?, H₂PO₄ ^?, Cl^?, Br^?, I^?, NO₃ ^? and HSO₄ ^? ions. The selectivity was ascribed to the synergistic effects arising from hydrogen bonding, electrostatic interaction and induced-fit process.     

The involvement of neutral species in the NO− → O+ charge inversion reaction

Intermediates in the overall charge inversion reaction NO^? → O⁺˙ (la), have been found to be O and NO˙ neutrals, and NO⁺ ions. The intermediates involved have been characterized by various mass spectrometric techniques; for example, inducing the steps of the reaction in separate field-free regions allows the peaks for the consecutive reactions NO^? → NO⁺ → O⁺˙ (II) to be recorded free from interference. However, to observe the involvement of a neutral intermediate, techniques such as floating the collision cell and applying a voltage to a deflector plate in front of the collision cell have been employed. Utilizing these methods allows a peak to be obtained due to one or both of the processes, NO^? → NO˙ → O⁺˙ (IIIa) and NO^? → O⁺˙ (IIIb), which cannot be separated. It is shown that the peak for the overall reaction NO^? → O⁺˙ can be modelled and reconstructed by addition of peaks, in a ratio of 1:3, produced by reactions II and III. This provides a reasonable account of the peak shape, in particular, of the tails of the peak which correspond to fragmentations involving large translational energy releases of up to 10 eV.     

Kinetic energy release distribution in the fragmentation of energy-selected iodopropane ions

The technique of threshold photoelectron-photoion coincidence (PEPICO) has been employed to determine the average kinetic energy release and the kinetic energy release distribution (KERD) for the iodine loss from 1- and 2-iodopropane ions as a function of the ion internal energy. The KERDs at all precursor-ion energies investigated (0–3 eV excess energy) have the shape of statistically expected distributions, 1-iodopropane ions which dissociate with an apparent 0.16 eV reverse activation barrier, are shown to isomerize at low energies prior to dissociation, to produce subsequently the 2-propyl C₃H₇^? structure. At high energies they may form a different C₃H₇^? isomer. The experimentally observed average kinetic energy releases are approximately a factor of 2 greater than expected statistically suggesting that not all vibrational modes participate in the energy disposal. The secondary dissociation of the C₃H₇^? isomers to C₃H₃ which is inhibited by a reverse activation barrier of = 0.4 eV indicates that the 1- and 2-iodopropane ions dissociate 75% and 60% respectively, to form the excited 1(²P_1/2) atoms.     

VUV photoionisation of free azabenzenes: Pyridine, pyrazine, pyrimidine, pyridazine and s-triazine

Photoionisation mass spectrometry was used to obtain the fragmentation pathways of pyridine, pyridazine, pyrimidine, pyrazine and s-triazine molecules upon absorption of 23.0, 15.7 and 13.8 eV synchrotron photons. The ionic fragments observed vary from molecule to molecule, however C₂H₂⁺, HCN⁺and HCNH⁺ are common to all five molecules at the three photon energies. Furthermore, the presence of C₂H₂N₂⁺, C₃H₃N⁺ and C₄H₄⁺ in the spectra of some of the molecules suggests dissociation pathways via loss of HCN moieties. The respective parent cations, m/q=79, 80 and 81 have a greater yield at low photon energies when compared to the most intense fragment peak in each spectra. We recorded two of the fragment cation yields, as well as the parent photoion yield curves of pyridine, pyridazine, and pyrimidine in the 8–30 eV range. The formation of abundant cation fragments show a strong propensity of the molecules for dissociation after the absorption of VUV photons higher than 14 eV. The differences in relative fragment yields from molecule to molecule, and when changing the excitation energy, suggest significant bond rearrangements and nuclear motion during the dissociation time. Thus, bond cleavage is dependent on the photon energy deposited in the molecule and on intramolecular reactivity. With the aid of photoion yield curves and energy estimations we have assigned major peaks in the spectra and discussed their fragmentation pathways.