A critical investigation of the effects of the radio frequency potential on the trapping of externally injected ions in ion trap mass spectrometry

The sensitivity of all ion trap mass spectrometry (ITMS) methods is dependent on the trapping efficiency of the instrument. For ITMS instruments utilizing external ion sources, such as laser desorption, trapping efficiency is known to depend on the phase and amplitude of the radio frequency (RF) potential applied to the ring electrode at the time of ion introduction. It is remarkable that, in a considerable body of literature, no consensus exists regarding the effects of these parameters on the efficacy of trapping externally generated ions. In this paper, a summary of the literature is presented in order to highlight significant discrepancies. New laser desorption ion trap mass spectrometry (LD-ITMS) data are also presented, from which conclusions are drawn in our effort to clarify some of the confusion. Copyright 1999 John Wiley & Sons, Ltd.     

Directional anisotropy of surface self-diffusion on Pt(110)

The rate of surface self-diffusion on a Pt(110) single crystal in the [1$\text{1}$0] and [001] directions was measured at 1200–1750 K by monitoring the decay of a sinusoidal surface profile. The surface diffusion rate in the [1$\text{1}$o] direction was much faster than in the [001] direction. The activation energy of surface self-diffusion was 1.70 and 3.16 eV for the [1$\text{1}$0] and [001] directions, respectively, in good agreement with theoretical estimates. For large amplitudes of the profile the decay rate for the [001] direction was also dependent on the amplitude. This behavior can be explained by the appearance of (111) facets on the profile, which cause a retardation of the profile decay.     

Electrochemical Processes for the Enrichment of Isotopes

The principles of electrochemical methods of isotope separation and the results obtained are described. The migration of ions in salt melts and solutions, complex formation in the homogeneous phase, electrolysis, ion-exchange equilibria, and exchange electrolysis are discussed in detail.     

One- and Two-Photon-Induced Photochemistry of Modified Palladium Porphyrazines Involving Molecular Oxygen

Abstract— Octaphenyltetraanthraporphyrazinato palladium undergoes a self-sensitized photoreaction in the presence of oxygen to form a substituted palladium phthalocyanine with four endoperoxide bridges. This compound exhibits photophysical behavior similiar to palladium tetra-tert- butyl-phthalocyanine. The phthalocyanine-palladium complex with four endoperoxide bridges ejects molecular oxygen when excited by consecutive two-photon absorption in the Q-band region at 662 nm. This photocyclo-reversion, which produces palladium porphyrazines bearing a diminished number of endoperoxide bridges, can occur up to four times per initial molecule. Irradiation of these photoproducts in the presence of oxygen produces substituted palladium phthalocyanine containing four endoperoxide groups.     

Pyrazolonderivate,VI: Eine13C-NMR Studie an Merocyaninen vom 2-Pyrazolin-5-on-Typ

The¹³C-chemical shifts ofN, N-disubstituted andN-monosubstituted 4-aminomethylene-2-pyrazolin-5-ones are reported and discussed. On the basis of coupling constants³ J(¹³C–H) it is demonstrated that the intramolecular hydrogen bond ofN-monosubstituted compounds1 b, c is not cleaved in a dipolar aprotic solvent, such asDMSO.     

Two-photon excitation of alkyl-substituted magnesium phthalocyanine: radical formation via higher excited states

The photophysical properties of tetra-(tert-butyl)-phthalocyanato-magnesium (t₄-PcMg) in solution and microheterogeneous systems (liposomes and micelles) were investigated. Radical cation formation occurs in chloroform during UV excitation in the presence of an electron acceptor (CBr₄). The same result is achieved by two-step absorption in the singlet manifold using pulsed excitation at λ_exc=670 nm, which is of interest from the viewpoint of photon delivery through the therapeutic window of tissues. To obtain a deeper insight into the photophysics leading to radical cation formation via the higher excited singlet state, the transient spectra and singlet—singlet absorption cross-sections were determined. In addition to strong excited state absorption within the spectral range of the Q_x-band, relatively large absorption cross-sections were also found in regions with low ground state absorption. The importance of these transitions for an effective two-colour excitation regime is discussed with regard to new start mechanisms for photodynamic laser tumour theraphy.     

Soil radon levels measured with SSNTD's and the soil radium content

The source of the radon gas ²²²Rn in the ground air is the soil and the bedrock underneath. The potential radon level in the ground is given by the content of ²²⁶Ra in the ground. The presence of ²²⁶Ra is in turn dependent on the amount of ²³⁸U in the ground, and these two isotopes are not always found to be in equilibrium in a sample of soil or bedrock. Especially if the soil is washed out, the radium content may be reduced. When the soil is the relevant source of the radon gas, it is interesting to look for a possible relation between the radon level and the radium content of the soil.

In this paper we report on measurements of soil radon level carried out with SSNTDs at several European sites. Soil samples were collected at these sites and analysed with gamma spectrometry to determine their radium content. A comparison of the different degree of disequilibrium of radon, defined as the ratio between the actual and the secular equilibrium-with-radium soil radon concentration, found at the different sites and depths is presented. The influence on the result of soil type and climate is briefly discussed.     

Surface self-diffusion on Pt(110): Directional dependence and influence of surface-energy anisotropy

The decay of periodic surface profiles by surface self-diffusion is simulated by numerically solving the phenomenological equations for this process. The crystalline nature of the surface is taken into account by introducing an anisotropic surface free energy,(). Depending on the degree of anisotropy of(), the decay kinetics and the shapes of the profiles are largely different. A comparison with measurements of profile decay on Pt(l10) single crystal surfaces shows that the anisotropy in() along the [1¯10] azimuth should be about 2–3%, while that along the [001] azimuth is expected near 8%. In the latter case large amplitude profiles exhibit (111) faceting and slow decay kinetics which are non-exponential. The rate of surface self-diffusion on Pt(110) is anisotropic with the [1¯10] direction being faster than the [001] direction.     

Synthese von Metallkomplexen des Tetra-(2,3-anthra)-tetraazaporphins und Vergleich ihrer Elektronenabsorptionsspektren mit denen anderer anellierter Tetraazaporphinsysteme

Copper, nickel and aluminium derivatives of tetra-2,3-anthratetraazaporphin bearing different substituents in the anthracen part have been prepared. The absorption spectra of these substances in different solvents are given and compared with metal complexes of other linearly annellated tetraazaporphins. In the series of vanadyl complexes of tetraazaporphin (_max 597 nm), tetra-[1,2-(4-tert-butyl)-benzo]-tetraazaporphin (_max 698 nm), tetra-[2,3-(6-tert-butyl)-naphtho]-tetraazaporphin (_max 807 nm), tetra-2,3-(anthra)-tetraazaporphin (_max 932 nm), tetra-2,3-(tetraceno)-tetraazaporphin (_max 1055 nm), the absorption maxima of the Q-band are shifted per annellated benzene ring about 100 nm to longer wave lengths.

     

The isoindolobenzazepine alkaloids

Three Chilean barberries, $\text{Berberis}$$\text{actinacantha}$ Mart. ex Schult., $\text{B}$. $\text{darwinii}$ Hook and [ulbar|B. $\text{valdiviana}$Phil. (Berberidaceae), have yielded several new isoindolobenzazepine and protoberberine alkaloids. Novel isoindolobenzazepines are (±)-13-deoxychilenine ($\text{a}$), pictonamine ($\text{10}$), chileninone ($\text{12}$), (±)-chileniimi ($\text{18}$) and (±)-palmanine ($\text{19}$). Highly oxidized protoberberines of particular interest include (±)-O-methylprechilenine ($\text{6}$) and (±)-prepseudopalmanine ($\text{21}$), together with 13-methoxy-8-oxyberberine ($\text{8}$). Isoindolobenzazepine alkaloids arise biogenetically from the rearrangement of highly oxidized protoberberines.