I Martinson

Ti 2p and O 1s X-ray absorption of TiO2 polymorphs

Abstract We present and discuss the Ti 2p and O 1s X-ray absorption spectra (XAS) and resonant photoelectron emission spectra (RPES) of the various polymorphic forms (TiO2-II, rutile and anatase) of TiO2. The largest differences between the Ti 2p XAS of polymorphs of TiO2 are observed in the region of the double peak structure of the L3 edge. A strong delocalization of the excited 3d electron in this region is concluded from the RPES at the L3 threshold of Ti. The differences in XAS are attributed to increasing strength of the crystal field caused by delocalization of the excited 3d electron.

Intercombination lines in delayed beam-foil spectra

The intrinsic time resolution of the beam-foil light source has been utilized in order to single out and to identify intercombination lines in the Mg i, Al i, and Si i isoelectronic sequences for ions with nuclear charge Z = 18–30 (Ar, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn). The method is described, and wavelength and lifetime data are presented. For the ions in the Al i and Si i sequences, the level positions of the high–spin term systems (lowest quartet and quintet levels, respectively) have been determined.

Lifetime Measurements in Mg I-Mg IV

We have investigated the beam-foil spectra of Mg (100-500 A, 2 000-5 000 A) using 100-360 keV Mg+ ions from a heavy ion accelerator. Transitions belonging to MgI-MgIV were observed and evidence was found for non-autoionizing doubly-excited states in MgII. Lifetimes were determined for several excited levels in MgI-MgIV. The results are compared with previous experimental data and accurate theoretical calculations.

Mean lives of excited terms in Be I, Be II, B I, B II, C II and C III

Abstract 25 mean lives of excited terms in Be I, Be II, B I, B II, C II and C III have been measured with the beam foil technique, using ion energies in the range 40–80 keV.

Multiplication of electronic excitations in CaO and YAlO3 crystals with free and self-trapped excitons

Using synchrotron radiation of 6-32 eV the reflection spectrum and excitation spectra for 5.7, 4.6 and 2.8 eV emissions have been measured for a freshly cleaved CaO crystal at LHeT. In CaO, indirect band-to-band transitions take place in the region of hv>or=6.4 eV. The excitation spectra for intrinsic emissions of 5.9 and 4.2 eV were measured in a YAlO3 crystal at LHeT as well. As in many other dielectrics the electron-hole mechanism of multiplication of electronic excitations connected with the creation of secondary electron-hole pairs by hot photoelectrons also occurs in CaO and YAlO3 crystals. The creation of secondary excitons by hot photoelectrons has been detected in YAlO3 for the first time. The excitonic mechanism of multiplication of electronic excitations has a high efficiency in crystals with self-trapping excitons of small radii.

Lifetimes for Excited Levels in Si I-Si IV

The beam-foil method has been used to measure lifetimes for six levels in Si I. The results are compared with emission data and theoretical values. Improved experimental values are also given for a number of previously measured levels in Si II-Si IV.

Mean lives of some excited levels of Li I and Li II.

A beam of 7Li+ ions accelerated to 56 keV by an electromagnetic isotope separator was directed through a thin carbon foil. The emergent ions were in various charge and excitation states, from which 26 spectral lines of Li i and Li ii were identified. The decay times of eight stronger lines were measured in order to determine the mean lives of upper levels involved in the decays.

Semi-Empirical Oscillator Strengths for the Cu I Isoelectronic Sequence

Semi-empirical values for the lifetimes, transition probabilities and oscillator strengths have been computed for all n = 4, n = 5 and some n ≤ 9 Rydberg transitions for ions in the Cu I isoelectronic sequence through In XXI. Extrapolation and interpolation techniques were utilised to obtain a set of estimated term values and ionisation potentials which, although crude by spectroscopic standards, are of sufficient accuracy to serve as inputs for transition probability calculations by the numerical Coulomb approximation.

Electric dipole transitions in ions of the N I isoelectronic sequence

The electric dipole transitions in the nitrogen isoelectronic sequence (Z = 10-30) between the levels of the 1s22s22p3, 1s22s2p4 and 1s22p5 configurations are considered. The stationary second-order many-body perturbation theory (MBPT) is used to account for the electron correlations. Non-local potential is used to calculate the radial part of the effective Hamiltonian. Relativistic corrections were included in the Breit-Pauli approximation. The results include energies, wavelengths, and oscillator strengths for all N-like ions in the interval Z = 10-30.

Doubly-excited Terms in Lithium and Beryllium

We give a summary of the available experimental information about doubly-excited terms in the Li I isoelectronic sequence and discuss some new classifications and lifetime measurements. Some new classifications in Be I are also suggested and we give the results of lifetime measurements for some singly-excited levels in Li II, Be I, and Be II.