VUV Dissociative Photoionization of Quinoline in the 7–26 eV Photon Energy Range

The dissociative photoionization of quinoline was studied by photoionization mass spectrometry and ion yield measurements over a synchrotron photon excitation energy range 7–26 eV. The ionic and neutral products were identified with the aid of thermochemical calculations that, in some cases, led to deeper understanding of photodissociation pathways and the determination of upper limits of heats of formation of ionic and neutral dissociation products. A detailed comparison between the 20 eV photon excitation and 70 eV electron impact mass spectra, coupled with estimation of thermochemical appearance energies, leads to assignment of the dissociative ionization cation and neutral products for each detected ion. Reaction schemes for formation of these products are proposed in a number of cases. Ion intensities in the photon and electron impact mass spectra were used to consider extending a rule of charge retention in simple bond cleavage to more complex cases of dissociative ionization.

NOTIZEN: Beiträge zur Chemie der Schwefelhalogenide, 13 [1] Das Photoionisations-Massenspektrum von SBr2 / Contributions to the Chemistry of Sulfur Halogenides, 13 [1] The Photoionization Mass Spectrum of SBr2

The photoionization mass spectrum of SBr2 has been m easured and the (S−Br)-bond energy has been calculated from experimental data.

Zur Photoionisation und Ionenfragmentation von SF4/Photoionization and Ion Fragmentation of SF4

The ionization potentials of sulfurtetrafluoride have been measured using threshold photoelectron spectroscopy and com pared with theoretical calculations. The decay of SF4 + has been studied by photoionization mass spectrometry and photoion-photoelectron coincidence. The break-down graphs reveal competing decay processes. Bond dissociation energies in SF4 + have been calculated.

1.1’-Bis-imidazyle und ihre Dissoziation in Radikale

Es wurden arylsubstituierte 1.1′-Bis-imidazyle dargestellt durch Umsetzung der Natriumsalze entsprechender Imidazole mit Brom. 1.1′-Bis-imidazyle dissoziieren in Lösung in Radikale. Die Dissoziation wurde mit Hilfe der Absorptionsspektren gemessen. Die Gleichgewichtskonstanten, Dissoziations-Enthalpien und Entropien werden mitgeteilt und diskutiert.

Photoreactions of Small Organic Molecules

The photoionization curves and the threshold energies for the molecules vinylchloride, vinylfluoride, 1,1-difluoroethylene and their abundant fragment ions have been measured with synchrotron radiation in the photon energy range from 10 - 23 eV. Appearance potentials were used to calculate heats of formation, bond energies and ionization potentials. The structure of ion efficiency curves is discussed in terms of different ionization processes.

Photoionenspektroskopie an Schwefelchloridpentafluorid SF5Cl, das Ionisationspotential von Schwefelpentafluorid SF5/Photoion Spectroscopy of Sulfurchloridepentafluoride SF5Cl, the Ionization Potential of Sulfurpentafluoride SF5

The appearance potentials of fragment ions from SF5Cl have been measured in the energy range 12 - 20 eV by means of photoionization mass spectrometry. From these data, the ionization potential of SF5 comes to 9.65 eV.

Photoionisationsmassenspektren von MethyI(trifluormethyl)sulfan CH3SCF3 [1]/Photoionization Mass Spectra of Methyl(trifluoromethyl)sulfan CH3SCF3 [1]

The ionization potential of CH3SCF3 and the appearance potentials of fragment ions have been measured in the photon energy range 9 -19 eV using synchrotron, radiation. From these results thermochemical data of CH3SCF3, CH3SCF3 + and fragment ions have been evaluated.

The Impact of Non-Electrolyte Impurities on the Nucleation Rate of Ice Ih

The nucleation rates of binary mixtures of water with dioxane, glycole, ethanol, i-propanol and urea have been investigated. Already at very low molar fraction (x = 0.002) of the additives a considerable decrease of the nucleation rates has been observed.

With increasing concentration of dioxane (x = 0.04 − 0.477) a strong decrease of the nucleation temperature related to the nucleation rate J = E6 −− E7 cm –3 s –1 has been observed; the maximum supercooling of 52.9 ℃ has been observed at x dioxane = 0.363.

The results of our experiments are in line with the correlated percolation model and with the interstitial model of liquid water.

Photoionization mass spectrometric study of the prebiotic species formamide in the 10-20 eV photon energy range

A photoion mass spectrometry study of the prebiotic species formamide was carried out using synchrotron radiation over the photon energy range 10-20 eV. Photoion yield curves were measured for the parent ion and seven fragment ions. The ionization energy of formamide was determined as IE (1(2)A') = 10.220 +/- 0.005 eV, in agreement with a value obtained by high resolution photoelectron spectroscopy. The adiabatic energy of the first excited state of the ion, 1(2)A'', was revised to 10.55 eV. A comparison of the ionization energies of related formamides, amino acids, and polypeptides provides useful information on the varied effects of methylation and shows that polymerization does not substantially alter the ionization properties of the amino acid monomer units. Assignments of the fragment ions and the pathways of their formation by dissociative photoionization were made on the basis of ion appearance energies in conjunction with thermochemical data and the results of earlier electron impact mass spectral studies. Some of the dissociation pathways are considered to involve coupling between the 1(2)A' ground state and the low-lying 1(2)A'' excited state of the cation. Heats of formation are derived for all ions detected and are compared with literature values where they exist. Formation of the HNCO(+) ion occurs by two separate paths, one involving H(2) loss, the other H + H. In the conclusion a brief discussion is given of some astrophysical implications of these results.

The Chemisorption of 2,3-Dimercapto-n-Propane Sulfonate at the Au(111)-Electrode

In this paper we report on the adsorption behaviour of 2,3-dimercapto-n-propan-sulfonate (DMPS) on the Au(111) electrode. DMPS is a water-soluble dithiol which is unstable in alkaline solution. The absorption decreases by 50 within two hours.The electrochemical behaviour is in accordance to that of other thiols, including monothiols. The interaction between sulfur and the Au(111) surface leads to a strong chemisorption in the double layer region which is limited by the reductive and oxidative desorption, respectively. The oxidative behavior (OD) of DMPS takes place simultaneously with the oxidation of the gold surface itself.We propose a mechanism for the OD which, in contrast to the well-known mechanism of the sulfur oxidation itself, includes the formation of a gold–sulfur complex. This OD mechanism acts like a corrosion and causes an increased roughness of the surface. Therefore, the charge consumed during the OD is exclusively due to the oxidation of Au0 to Au3+ in form of the complex and in form of the well-known Au2O3 oxide.

The Freezing of n-Alkanes C15H32 and C17H36: An Unsual Mechanism of Homogeneous Nucleation

The nucleation kinetics of n-alkane droplets with carbon numbers of 15 and 17 was observed in an electrodynamic balance. Changes in the elastic light scattering pattern of the single levitated microdroplets indicate the phase transition liquid to solid. Measurements of the nucleation rates gave information on the dynamics of the nucleation process and allow to propose a new mechanism for the nucleation. Large induction times observed for the C15H32 droplets indicate that the nucleation starts after a solid layer has been built up at the surface.

Ion Pair Formation of Sulfur Dioxide in the Energy Range 14–20 eV

The photoinduced ion yield curve of O- from gaseous sulfur dioxide shows remarkable structures in the energy range between 14 and 20 eV. Their analysis reveals that they image different vibrationless and vibrationally excited Rydberg states converging to the ionic states C, D, E, F. In addition S-, SO- and SO2 - have been observed. Besides ion pair formation small contributions from dissociative electron attachment are recognized.

The absorption spectra of anisole-h8, anisole-d3 and anisole-d8. The assignment of fundamental vibrations in the S0and the S1states

The REMPI spectra of anisole-h8, anisole-d3 and anisole-d8 have been measured. The assignment of the fundamental vibrations of anisole in the S(1) state is supported by quantum chemical model calculations, the isotopic shifts, the comparison with the frequencies of corresponding vibrations in other monosubstituted benzenes, especially phenol, and the overtones, combinations and progressions observed in the spectrum of anisole-h8. The frequencies of the 42 fundamental vibrations of anisole in the S(1) state are evaluated and compared with the frequencies of the corresponding vibrations in the electronic ground state. Some assignments given earlier in the literature have been revised.