S Huldt

The Spectrum and Term System of Singly Ionized Titanium, Ti II

The TiII spectrum has been recorded in the region 1100-11 000 A. 1240 lines have been classified as transitions between 204 levels of the configurations (3d + 4s)3, 3d2 nl (nl = 5, 6s; 4, 5p; 4, 5d; 4f) and 3d4s4p. Parametric studies including configuration interaction have been carried out for a number of configurations. The ionization energy has been determined to 109 494 ± 20 cm-1.

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.

Absolute Cross Sections for Multielectron Processes in Slow Arq+ + Ne, Ar, Kr Collisions

Absolute cross sections for single and multielectron processes in 1.8q keV collisions, Arq+ + B → Arr+ + Bs+ + (s + r - q)e- have been measured for the targets Ne, Ar and Kr. By means of a coincidence time-of-flight technique, the charge state of the projectile before and after the collision and the charge state of the target ion are determined. The projectile charge ranges from one to nine, while s at most reaches six (Kr), five (Ar) and four (Ne). The experimental technique is discussed and a simple model for absolute cross sections σq,rs is proposed.

Transitions in Multiply Excited FVI and FVII

The transitions 1s2s2p2 5P-1s2p3 5S0 in F VI and 1s2s2p 4P0-1s2p2 4P in F VII have been investigated using the method of beam-foil spectroscopy. The fine-structure separations have been determined for the 1s2s2p2 5P term in F VI and for both 4P terms in F VII. The results are compared with recent theoretical calculations of fine structure, based on relativistic wavefunctions, and with previous experimental data. Lifetime measurements are reported for the 1s2p2 4P5/2 level and the 1s2p3 5S20 level.

Stray light suppression in spectroscopy using periodic shadowing

It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity.

Radiative Lifetimes and Hyperfine Induced Decay of the 1s 2p 3P2 and 3P0 Levels in Al XIII

The transitions 1s2s 3S1-1s2p 3P2 and 1s2s 3S1-1s2p 3P0 in He-like Al have been observed in a beam-foil experiment at 900 ± 1 A and 953 ± 1 A, respectively. The lifetimes of the upper levels have been determined to 5.4 ± 0.2 ns (3P2) and 4.8 ± 0.2 ns (3P0). We have observed a shortening of the 2p 3P0 lifetime in agreement with theories which consider hyperfine quenching effects, and we give an estimate of the quenching of the level. The wavelengths are compared with theoretical values which include Lamb shift.

Lifetimes for Low-lying Levels in Zn I and Zn II

Lifetime measurements using the beam-foil technique have been made for levels in Zn I and Zn II. The following results (in ns) were obtained: ZnI, 4s4p 1P (1.33 ± 0.07), 4s4d 1D (20.5 ± 1.5), 4s4d 3D (5.4 ± 0.6); Zn II, 4p 2P (2.07 ± 0.20), 4d 2D (1.40 ± 0.15), 5s 2S (1.8 ± 0.2), 5p 2P (17 ± 2). These results are compared with previous experimental and theoretical results and the origins of certain disagreements are analyzed.

Trapping of Non-Resonance Radiation in Atoms and its Influence on Measured Lifetimes of the 4p and 5p Levels in Ar I

Lifetimes of 17 levels of the 3p5 4p and 3p5 5p configurations in Ar I have been measured using the High Frequency Deflection technique at target pressures in the range 0.04-10 mtorr. An anomalous pressure dependence is found which indicates that the studied 4p, 5p → 4s (non-resonance) transitions are subjected to trapping effects which occur because of exceptionally long lifetimes of the 4s levels due to either 4s → 3p resonance trapping (4s, J = 1) or metastability (4s, J = 0, 2). A theoretical fit to the observed pressure dependence based upon this process is given as well as corrected zero pressure lifetimes which in several cases are considerably shorter than earlier published values.

Transition Probabilities for the 1s2 1S0-1s2p3P1 Intercombination Line in He-Like Carbon and Nitrogen

Lifetime measurements are presented for the 1s2p 3P1,2 levels for He-like C V and N VI. From the measured lifetimes, transition probabilities are deduced for both allowed and spin-forbidden transitions. The values for the 1s2 1S0 - 1s2p 3P1 transition rates, 0.29 × 108 and 1.38 × 108 s-1 for C V and N VI respectively, are found to be in good agreement with theory.

Accurate Experimental Lifetimes of Excited Levels in Sodiumlike Sulfur, S VI

The lifetimes of the terms 3p 2P, 3d 2D, 4s 2S, 4p 2P, 4d 2D, 4f 2F, 5g 2G, 6g 2G, 6h 2H, 7h 2H, 7i 2I and 8k 2K in sodiumlike sulfur, S VI, have been determined using the beam-foil excitation technique. Most of the decay curves were analyzed by means of the ANDC method which corrects for cascading in a very detailed way. Accurate results were thereby obtained which show that an excellent agreement exists between experimental and theoretical values. Some previously noted disagreements between the results of beam-foil experiments and theoretical investigations are explained as being due to less accurate analyses of the experimental data.