Nina Reistad

Observation of an intensity anomaly in the 3s23p 2P1/2,3/2-3s3p2 2S1/2 and 2P1/2 resonance transitions in the Al I isoelectronic sequence

The intensity ratio of the two fine structure components in the 3s23p 2PJ–3s3p 2S1/2 and 2P1/2 resonance transitions has been measured in Al-like S IV, Cl V, Ar VI and Ti X, using the beam-foil technique. Unexpectedly large deviations from the LS ratios are found, particularly in the 2P–2S case. Although these deviations can be understood qualitatively from theoretical calculations (also reported), large quantitative discrepancies are observed in the beginning of the sequence.

J-Dependent 3s4p 3PJ Lifetimes in Mg-Like Sulphur and Chlorine

An experimental and theoretical study of the lifetimes of the 3s4p 3P levels in S V and Cl VI is reported. Using the beam-foil technique and extensive cascade corrections with the ANDC method we obtain the following lifetimes in ns: 0.72 ± 0.07 (3P2) and 0.37 ± 0.04 (3P1) in S V, whereas both levels have the same lifetime, 0.24 ± 0.03 ns, in Cl VI. The theoretical analysis shows that the large lifetime difference in S V results from a mixing of the 3s4p 1P1 and 3P1 levels, which is enhanced by interactions between the 3s4p and 3p3d configurations. Calculated transition probabilities for the individual decay channels from the 3s4p 3P levels are also given. In addition, the theoretical analysis indicates an erroneous identification of the 3p3d 1P and 1F levels in S V.

Lifetimes of Levels in C II and C III, Derived from Beam-Foil Experiments and Extensive Cascade Analyses

Using the beam-foil excitation technique and the ANDC method for cascade corrections, we have determined lifetimes of the 2s2p2 2S, 2s2ns 2S (n = 3, 4, 5), 2s2p2 2P, 2s2np 2P0 (n = 3, 4), and 2p3 2P0 terms in C II and the 2s2p 1P0 level in C III. The new experimental lifetimes are in very good agreement with the results of recent theoretical calculations.

The 2p4 3s, 3p and 3d Configurations of Thirteen Times Ionized Titanium, Ti XIV

The spectrum of Ti XIV has been observed in the wavelength region 80-550 A using the fast ion beam spectroscopy method. 47 lines have been identified as transitions between the 2p4 3s, 3p, and 3d configurations in the 360-540 A interval. The level identifications are supported by comparisons between observations and Hartree-Fock calculations along the F I isoelectronic sequence.

On the 3s-3p and 3p-3d Transitions in Ne-like Ni XIX

An experimental and theoretical study has been made of the 3s-3p and 3p-3d transitions in Ni XIX. The method of beam-foil spectroscopy, using 30-64 MeV Ni ions from a tandem accelerator, has been combined with theoretical calculations using the multiconfiguration Dirac-Fock (MCDF) program.

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.

Oscillator Strength Measurements of the Resonance Transitions in Sodium- and Magnesium-Like Argon

We have used the beam-foil technique to measure the decay of the 3p 2P1/2, 2P3/2 and 3d2D3/2, 2D5/2 levels in Ar VIII and the 3s3p 1P, 3s3d 1D, 3p2 1S, and 1D levels in Ar VII. Applying the ANDC method of analysis, accurate lifetimes for the 3p 2P1/2, 2P3/2 and 3s3p 1P levels have been determined. The corresponding oscillator strengths are found to be in very good agreement with theoretical values. A comparison between theoretical and experimental f-values for the resonance transitions in the Na I isoelectronic sequence is also presented.

Diffuse Reflectance Spectroscopy for Surface Measurement of Liver Pathology

Background: Liver parenchymal injuries such as steatosis, steatohepatitis, fibrosis, and sinusoidal obstruction syndrome can lead to increased morbidity and liver failure after liver resection. Diffuse reflectance spectroscopy (DRS) is an optical measuring method that is fast, convenient, and established. DRS has previously been used on the liver with an invasive technique consisting of a needle that is inserted into the parenchyma. We developed a DRS system with a hand-held probe that is applied to the liver surface. In this study, we investigated the impact of the liver capsule on DRS measurements and whether liver surface measurements are representative of the whole liver. We also wanted to confirm that we could discriminate between tumor and liver parenchyma by DRS. Materials and Methods: The instrumentation setup consisted of a light source, a fiber-optic contact probe, and two spectrometers connected to a computer. Patients scheduled for liver resection due to hepatic malignancy were included, and DRS measurements were performed on the excised liver part with and without the liver capsule and alongside a newly cut surface. To estimate the scattering parameters and tissue chromophore volume fractions, including blood, bile, and fat, the measured diffuse reflectance spectra were applied to an analytical model. Results: In total, 960 DRS spectra from the excised liver tissue of 18 patients were analyzed. All factors analyzed regarding tumor versus liver tissue were significantly different. When measuring through the capsule, the blood volume fraction was found to be 8.4 ± 3.5%, the lipid volume fraction was 9.9 ± 4.7%, and the bile volume fraction was 8.2 ± 4.6%. No differences could be found between surface measurements and cross-sectional measurements. In measurements with/without the liver capsule, the differences in volume fraction were 1.63% (0.75-2.77), -0.54% (-2.97 to 0.32), and -0.15% (-1.06 to 1.24) for blood, lipid, and bile, respectively. Conclusion: This study shows that it is possible to manage DRS measurements through the liver capsule and that surface DRS measurements are representative of the whole liver. The results are consistent with data published earlier on the combination of liver chromophores. The results encourage us to proceed with in vivo measurements for further quantification of the livers composition and assessment of parenchymal damage such as steatosis and fibrosis grade.

A new measurement of the 1s2s2p 4P0-1s2p2 4P transitions in C IV: wavelengths, fine structure intervals and lifetimes

The Δn = 0 transition multiplet connecting the lowest quartet states of doubly excited C IV has been studied by beam-foil spectroscopy. The fine structure splittings obtained for the 1s2s2p 4P0 and 1s2p2 4P terms confirm previous experimental results with an improved accuracy. The average transition wavelength λc.g. = (1344.49 ± 0.04)A is now more precisely determined by about a factor of eight. At the new level of precision this value shows a small but significant deviation from the best theoretical predictions. The lifetimes of the 1s2p2 4P levels have been determined as τ = (0.71 ± 0.07)ns for 4P5/2 and τ = (1.66 ± 0.13)ns for 4P3/2. The latter value disagrees with previous experimental results but is in excellent agreement with an isoelectronic trend analysis.

Lifetime of the 3s3p 1P Term in S V

The lifetime of the 3s3p 1P term in Mg-like S V has been determined by beam-foil spectroscopy in combination with detailed analyses of cascading processes by means of the ANDC technique. One of the most important cascade transitions was found to be seriously blended by a strong S VII transition. An earlier proposed method for applying the ANDC formalism to correct for blending has been tested for the first time and found to work very well. The resulting 3s3p 1P lifetime of 0.19 ± 0.01 ns, corresponding to an absorption oscillator strength of 1.46 ± 0.08, is in good agreement with recent theoretical values. Some previously noted discrepancies between beam-foil measurements and theoretical calculations for Mg-like ions can now be explained as being due to insufficient cascade corrections in previous experimental work.