Sökning: "radiative lifetimes"

Visar resultat 16 - 20 av 22 avhandlingar innehållade orden radiative lifetimes.

1. 16. Time-Resolved Spectroscopy and Intensity Measurements of Singly Charged Ions

   Författare :Erik Bäckström; Sven Mannervik; Andreas Wolf; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; fysik; Physics;

   Sammanfattning : This thesis is mainly concerned with investigations of spontaneous radiatively decaying states in both negative and positive singly charged ions. When possible, the measured lifetime of the state has been combined with branching fractions in order to derive the absolute transition probability (A-value) between different quantum states. LÄS MER

3. 17. Measurements of High-Precision Atomic Data with Applications to Astrophysics and Cosmology

   Författare :Maria Aldenius; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; atomic data; Ca; Cr; Fe; Mn; Mg; metal-poor stars; fine-structure constant; Fourier transform spectroscopy; nebulae; oscillator strengths; spectroscopy; wavelengths; Ti; Zn; Astronomy; Astronomi; Atomic and molecular physics; Atom- och molekylärfysik; rymdvetenskap; space research; cosmic chemistry; kosmisk kemi; branching fractions;

   Sammanfattning : Investigations of astrophysical spectra require accurate atomic data, such as wavelengths and transition probabilities. This thesis provides high-precision atomic data for astrophysical and cosmological applications. The measurements have been carried out using Fourier transform spectrometry on light produced in a hollow cathode light source. LÄS MER

4. 18. Computational Atomic Structures Toward Heavy Element Research

   Författare :Sacha Schiffmann; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Atoms; electron correlation; relativity; Quantum mechanics; calculations; natural orbitals; isotope shifts; hyperfine structures; transition parameters; Landé g factor; Fysicumarkivet A:2021:Schiffmann;

   Sammanfattning : We are interested in complex electronic structures of various atomic and ionics systems. We use an ab initioapproach, the multiconfigurational Dirac-Hartree-Fock (MCDHF), to compute atomic structures and properties. LÄS MER

5. 19. Impact of carrier localization on recombination in InGaN quantum wells with nonbasal crystallographic orientations

   Författare :Ruslan Ivanov; Saulius Marcinkevičius; Nicolas Grandjean; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; InGaN; quantum well; semipolar; nonpolar; near-field microscopy; carrier localization; carrier transport; optical polarization; Fysik; Physics;

   Sammanfattning : The modern InGaN technology demonstrates high efficiencies only in the blue spectral region and low current operation modes. The growth of InGaN quantum wells (QWs) on nonbasal crystallographic planes (NBP) has potential to deliver high-power blue and green light emitting diodes and lasers. LÄS MER

7. 20. Atomic Electrons as Sensitive Probes of Nuclear Properties and Astrophysical Plasma Environments : A Computational Approach

   Författare :Asimina Papoulia; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Fysicumarkivet A:2021:Papoulia; Computational atomic structure; Relativistic atomic theory; Transition probabilities; Abundance analysis; Landé g­-factors; Hyperfine structure; Nuclear quadrupole moments; Isotope shift; Field shift; Nuclear deformation;

   Sammanfattning : This thesis deals with the relativistic modeling of atoms and ions. To interpret the stellar spectra and gain more insight from astrophysical observations, the underlying processes that generate the spectra need to be well understood and described. LÄS MER