Exploring new mass regions with the ISOLTRAP spectrometer

First direct mass measurements on rare earth isotopes around ¹⁴⁶Gd have been performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. More than 40 isotopes of the elements Pr, Nd, Pm, Sm, Eu, Dy and Ho have been measured with an accuracy of typically 1 × 10^-7. In the case of ¹⁴¹Sm isomeric and ground state (ΔE = 175 keV) were resolved. Since isobaric contaminations are present in the ISOLDE beam, these measurements on rare earth isotopes became only possible after the installation of a new cooler trap which acts an isobar separator. This revised version was published online in August 2006 with corrections to the Cover Date.     

Anomalous behaviour of electron mobility in space charge layers

The Hall effect on polar faces of ZnO has been measured at 80 K. Surface excess electron densities between 10⁷ and 10¹³ cm^?2 have been achieved by photolysis, annealing or hydrogen exposure. The surface electron mobility as a function of carrier density shows a modulated structure. Possible scattering mechanism are discussed.     

Binding states of zinc on the polar faces of Zno

The desorption of zinc from cleaved polar faces was investigated in UHV. TDS (calibrated by evaporation of metallic Zn), surface conductivity, LEED and AES were used. The initial sticking coefficient is lower on the Zn face than on the O face, 0.2 and 1 respectively. On both faces two states of adsorption occur. The lower state on the Zn face has an activation energy of 35 kcal/mole(1.5 eV). The corresponding energy on the oxygen face is 16 kcal/mole (0.7 eV). The lower peak is connected with an increase in surface conductivity on both faces. On the Zn face this surface conductivity can be attributed to a surface donor 1.3 eV above the conduction band edge. Above one monolayer the formation of islands and an epitactical growing of a zinc lattice were found.     

One‐ and two‐photon activity of cross‐conjugated photoinitiators with bathochromic shift

Intrigued by the good performance of 1,5‐diphenylpenta‐1,4‐diyn‐3‐one ( DPD ) as photoinitiator for radical polymerization we prepared and investigated several donor substituted derivatives. UV‐Vis spectroscopy revealed a gradual red‐shift of λ_max and higher extinction in the order of the donor capability. A methoxy‐substituted derivative ( O‐DPD ) exhibited significant photoinitiation activity in photo‐DSC experiments. Steady state photolysis experiments showed decreased decomposition rates with increasing donor capability. A dimethylamino derivative N‐DPD was even photostable under these conditions. Because of to the D‐π‐A‐π‐D system of these compounds two‐photon induced 3D photopolymerization experiments were performed and N‐DPD showed outstanding performance compared to often applied single photon initiators. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3280–3291, 2007