Evaluation of Luminescence Decay Measurements Probed on Pure and Doped Pt(IV) Hexahalogeno Complexes. II. Molecular Properties Obtained from Temperature Dependent Lifetime Curves

1997 ◽  
Vol 52 (5) ◽  
pp. 447-456
Author(s):  
Ingo Biertümpel ◽  
Hans-Herbert Schmidtke
Keyword(s):  
Excited States ◽  
Ground State ◽  
Energy Levels ◽  
Decay Rates ◽  
Rate Equations ◽  
Temperature Dependent ◽  
Lifetime Measurements ◽  
Thermally Activated ◽  
Ground State Energies ◽  
Higher Excited States

Abstract Lifetime measurements down to nearly liquid helium temperatures are used for determining energy levels and transition rates between excited levels and relaxations into the ground state. Energies are obtained from temperature dependent lifetimes by fitting experimental curves to model functions pertinent for thermally activated processes. Rates are calculated from solutions of rate equations. Similar parameters for pure and doped Pt(IV) hexahalogeno complexes indicate that excited levels largely belong to molecular units. Some of the rates between excited states are only somewhat larger than decay rates into the ground state, which is a consequence of the polyexponential decay measured also at low temperature (2 K). In the series of halogen complexes, the rates between spinorbit levels resulting from 3T1g increase from fluorine to bromine, although energy splittings become larger. Due to the decreasing population of higher excited states in this series, K^PtFö shows a tri-exponential, K2PtCl6 a bi-exponential and FoPtBr6 a mono-exponential decay. In the latter case the population density of higher excited states relaxes so fast that emission occurs primarily from the lowest excited Γ3(3T1g) level. Phase transitions and emission from chromophores on different sites can also be observed.

scholarly journals X-ray laser lines in nickel-like erbium

2016 ◽  
Vol 94 (8) ◽  
pp. 705-711
Author(s):  
Wessameldin S. Abdelaziz
Keyword(s):  
Ionization Potential ◽  
Excited States ◽  
Ground State ◽  
Energy Levels ◽  
Single Electron ◽  
Electron Densities ◽  
X Ray ◽  
Electron Excited States

Energy levels of 249 excited levels in nickel-like erbium are calculated using the 3s23p63d10 as a ground state and the single electron excited states from n = 3 to n = 4, 5 orbitals, calculations have been performed using FAC code (Gu. Astrophys. J. 582, 1241 (2003). doi:10.1086/344745 ). The populations are calculated over electron densities from 1020 to 1023 cm−3 and electron temperatures 1/2, 3/4 of the ionization potential of Ni-like Er. The gain coefficients of the transitions are calculated.

scholarly journals Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

Inorganics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 14
Author(s):  
Patrick Herr ◽  
Oliver S. Wenger
Keyword(s):  
Excited State ◽  
Excited States ◽  
Quantum Yields ◽  
Nonradiative Relaxation ◽  
Temperature Dependent ◽  
Tert Butyl ◽  
Thermally Activated ◽  
Ligand Charge Transfer ◽  
Order Of Magnitude ◽  
Electronic Ground

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.

Excited states of positronium in positron–hydrogen charge exchange

1978 ◽  
Vol 56 (5) ◽  
pp. 565-570 ◽  
Author(s):  
V. S. Kulhar ◽  
C. S. Shastry
Keyword(s):  
Excited States ◽  
Charge Exchange ◽  
Cross Sections ◽  
Ground State ◽  
Born Approximation ◽  
Energy Region ◽  
Hydrogen Charge ◽  
Positronium Formation ◽  
State Approximation ◽  
Higher Excited States

The two state approximation method for the study of the rearrangement collisions is applied to the process of positronium formation in excited states for positron–hydrogen charge exchange collisions. Differential and integrated cross sections are computed for positronium formation in 2S, 2P, and 3S excited states. The results obtained in the energy region 2 to 10 Ry are compared with positronium formation cross sections in ground state. Total positronium formation cross sections including the contributions of capture into all the higher excited states of positronium are also computed in the first Born approximation and the two state approximation in the energy region considered.

DENSITY FUNCTIONAL STUDY ON THE PROTON ASSISTED ISOMERIZATION OF 1H-IMIDAZO(4,5-b)PYRIDINE DERIVATIVES

2012 ◽  
Vol 11 (03) ◽  
pp. 651-661 ◽  
Author(s):  
R. P. DEKA ◽  
C. MEDHI
Keyword(s):  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Energy Levels ◽  
Relative Energy ◽  
Functional Study ◽  
Pyridine Derivatives ◽  
Energy Gaps ◽  
Free Molecules ◽  
Pass Through

The proton assisted isomerization reactions of 1H-imidazo(4,5-b)pyridine (IMP) derivatives have been studied by using B3LYP/6-31G + (d,p) calculations, and the transition states of the reactions are analyzed with B3LYP/6-31+G(d,p) opt=qst3 route. It has been found that the prototropic transformation could be the feasible pathway of isomerization, since the energy gaps between the various protonated isomers are found closer compared to free molecules. The conversion of IMP-a1 to IMP-b1 may pass through several protrotopic isomerization, since the activation energy as well as the relative energy levels of these isomers are not small compared to other pathways. However, the results suggest that some of the reactions may take place simultaneously through protrotopic transformation. The relative variations of energy gaps in the excited states are smaller than the ground states. The protrotropic transformation in the excited states may be more feasible than the ground state.

A group theoretical approach to the many nucleon problem

1971 ◽  
Vol 70 (3) ◽  
pp. 485-496 ◽  
Author(s):  
J. A. de Wet
Keyword(s):  
Angular Momentum ◽  
Theoretical Approach ◽  
Ground State ◽  
Mass Number ◽  
Energy Levels ◽  
Quantum Numbers ◽  
The Many ◽  
Special Case ◽  
Ground State Energies ◽  
Good Agreement

Representations of the four-dimensional unitary group U4 were considered long ago by Wigner(1)as a model for nuclear isobaric multiplets. However, the Hamiltonian did not include the components of isospin which together with the spin coordinates are known to label the nuclear states. In this paper we shall find representations characterized by the eigenvalues of angular momentum J, isospin T and parity π, and will find mass relations which give good agreement with the experimental energy levels of Li6 and Be8 labelled by the same quantum numbers. The representations found by Wigner give good results for the ground state energies, or masses, of all the nuclei up to a mass number of A = 110(2), and we shall derive Wigner's representations as a special case. In fact, unless these are satisfied it is impossible for particle-like representations of U4 to exist!

scholarly journals Optical Spectroscopy of Li6Y(BO3)3 Single Crystals Doped with Dysprosium

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 503
Author(s):  
Éva Tichy-Rács ◽  
Ivo Romet ◽  
László Kovács ◽  
Krisztián Lengyel ◽  
Gábor Corradi ◽  
...  
Keyword(s):  
Low Temperature ◽  
Optical Absorption ◽  
Single Crystals ◽  
Crystal Field ◽  
Excited States ◽  
Ground State ◽  
Energy Levels ◽  
Luminescence Spectroscopy ◽  
Wide Spectral Range ◽  
Low Symmetry

The energy levels of Dy3+ ions have been determined in lithium yttrium borate (Li6Y(BO3)3) single crystals in a wide spectral range between 3000 and 40,000 cm−1 using optical absorption and luminescence spectroscopy, which also allow for an analysis of the ground state. The crystal field splittings of the 6H15/2 ground state and all excited states up to the 4F7/2 manifold were obtained at a low temperature, based on luminescence (T = 4.2–78 K) and absorption (T = 8–100 K) measurements, respectively. The numbers of experimentally observed Stark sublevels are in agreement with those expected theoretically for Dy3+ ions occupying a single low symmetry (C1) site.

scholarly journals On Anomalous Fluorescence of Symmetrical Polymethine Dyes

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
P. O. Kondratenko ◽  
Yu. M. Lopatkin
Keyword(s):  
Excited States ◽  
Ground State ◽  
Internal Conversion ◽  
Polymethine Dyes ◽  
Necessary Condition ◽  
Relaxation Processes ◽  
Sufficient Condition ◽  
Radiative Relaxation ◽  
Higher Excited States ◽  
Group Theoretical Analysis

The group-theoretical analysis of polymethine dyes (PMD) showed that relaxation processes between the states S3 and S1 are forbidden, either by radiation or by internal conversion. From the state S3, only transition to the ground state of the molecule is possible. Since the experimental data state that the quantum yield of S3 ⟶ S0 fluorescence does not exceed 1%, it is indicated that the internal conversion rate can be 2 orders of magnitude higher than the radiative relaxation rate of the molecule. Concerning the reasons for the appearance of fluorescence from the higher excited states of molecules, it can be asserted that the necessary condition for the appearance of S3 ⟶ S0 fluorescence is the absence of S0 ⟶ S1(v)-absorption in the region of the S0 ⟶ S3 transition. The sufficient condition is the corresponding symmetry of the excited states, which imposes a prohibition on the S3 ⟶ S1 relaxation process.

Spectroscopic study of EUV and SXR spectral lines with partition function and level population of W LVI

2021 ◽  
Author(s):  
Rinku Sharma ◽  
Richa Paijwar
Keyword(s):  
Partition Function ◽  
Excited States ◽  
Extreme Ultraviolet ◽  
Energy Levels ◽  
Calculated Data ◽  
Spectral Lines ◽  
Thermodynamic Quantities ◽  
Excitation Energies ◽  
Relative Population ◽  
Higher Excited States

We present comprehensive and elaborate study of W LVI (K-likeW55+) by using multi-configuration Dirac-Fock method (MCDF). We have included relativistic corrections, QED (Quantum electrodynamics) and Breit corrections in our computation. We have reported energy levels and radiative data for multipole transitions i.e. electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) within lowest 142 fine structure levels and predicted soft x-ray transition (SXR) and extreme ultraviolet transitions (EUV) from higher excited states to ground state. We have compared our calculated data with energy levels compiled by NIST and other available results in literature and small discrepancies found with them are discussed. Since only few lowest levels are only available in the literature, therefore for checking excitation energies of higher excited states, we have performed same calculations with distorted wave method. Furthermore, we have also provided relative population for first five excited states, partition function and thermodynamic quantities for both W LVI and studied their variations with temperature. We believe that our reported new atomic data of W LVI may be useful in identification and analysis of spectral lines from various astrophysical and fusion plasma sources and also beneficial in plasma modeling.

scholarly journals Nuclear Weak Processes in Presupernova Stars

1996 ◽  
Vol 145 ◽  
pp. 165-172
Author(s):  
A. Ray ◽  
T. Kar ◽  
S. Sarkar ◽  
S. Chakravarti
Keyword(s):  
Excited States ◽  
Beta Decay ◽  
Ground State ◽  
Strength Function ◽  
Supernova Explosion ◽  
Decay Rates ◽  
Distribution Method ◽  
The Core ◽  
Weak Transition ◽  
Late Stages

The structure and the size of the core of massive presupernova stars are determined by the electron fraction and entropy of the core during its late stages of evolution; these in turn affect the subsequent evolution during gravitational collapse and supernova explosion phases. Beta decay and electron capture on a number of neutron rich nuclei can contribute substantially towards the reduction of the entropy and possibly the electron fraction in the core. Methods for calculating the weak transition rates for a number of nuclei for which no reliable rates exist (particularly for A > 60) are outlined. The calculations are particularly suited for presupernova matter density (p = 107 - 109 g/cc) and temperature (T = 2 - 6 × 109 °K). We include besides the contributions from the ground state and the known excited states, the Gamow-Teller (GT) resonance states (e.g. for beta decay rates, the GT+ states) in the mother nucleus which are populated thermally. For the GT strength function for transitions from the ground state (as well as excited states) we use a sum rule calculated by the spectral distribution method where the centroid of the distribution is obtained from experimental data on (p,n) reactions. The contribution of the excited levels and GT+ resonances turn out to be important at high temperatures which may prevail in presupernova stellar cores.

scholarly journals Cis–trans isomerism modulates the magnetic relaxation of dysprosium single-molecule magnets

2016 ◽  
Vol 7 (6) ◽  
pp. 3632-3639 ◽  
Author(s):  
Jianfeng Wu ◽  
Julie Jung ◽  
Peng Zhang ◽  
Haixia Zhang ◽  
Jinkui Tang ◽  
...  
Keyword(s):  
Excited States ◽  
Single Molecule ◽  
Magnetic Relaxation ◽  
Energy Levels ◽  
Single Molecule Magnets ◽  
Higher Excited States

The rotation of the coordinating plane of the square-antiprismatic environment induces a magnetic relaxation path through higher excited states, offering a new way to modulate the geometries of lanthanides to facilitate magnetic relaxation climbing up to higher energy levels.

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