scholarly journals Recombination Lasers in the XUV Spectral Region

1984 ◽  
Vol 86 ◽  
pp. 234-240
Author(s):  
G.J. Pert
Keyword(s):  
Transition Probability ◽  
Unit Length ◽  
Energy Levels ◽  
Ultra Violet ◽  
Statistical Weight ◽  
Laser Medium ◽  
Total Power ◽  
Spontaneous Transition ◽  
Spectral Bands ◽  
Conventional Laser

In a conventional laser operating in the near ultra-violet, optical or infra-red spectral bands the photon energies, not exceeding lOeV, are closely matched to the electronic or molecular energy levels of neutral and weakly ionised atoms. Consequently typical photon energies (~ eV), and transition lifetimes (~ ns) closely match the characteristics of fast electrical circuitry feeding a weakly ionised discharge which may be used to pump either directly or indirectly the laser medium.In a X-ray laser operating at about 10Å, photon energies are about 1 keV, and lifetimes about 10−14s (l0fs). In consequence the power required to pump the laser must be expected to increase rapidly as the wavelength decreases. The gain per unit length is given by:where ζ is the line shape factor, A the spontaneous transition probability, λ the wavelength, and Δν the width of the line, and (n2,g2) and (n3,g3) the population density and statistical weight of the lower and upper laser states respectively. The total power loss per unit area, p, of the medium must exceed that emitted by spontaneous decay of the laser transition.

Energy Levels and Electromagnetic Transition of 90-94mo Nuclei Using Ibm-1

2020 ◽  
pp. 149-152
Keyword(s):  
Experimental Data ◽  
Transition Probability ◽  
Energy Levels ◽  
Dynamical Symmetry ◽  
Interacting Boson Model ◽  
Excitation Energies ◽  
Electromagnetic Transition ◽  
Boson Model ◽  
Energy States ◽  
Good Agreement

The energy states for the J , b , ɤ bands and electromagnetic transitions B (E2) values for even – even molybdenum 90 – 94 Mo nuclei are calculated in the present work of "the interacting boson model (IBM-1)" . The parameters of the equation of IBM-1 Hamiltonian are determined which yield the best excellent suit the experimental energy states . The positive parity of energy states are obtained by using IBS1. for program for even 90 – 94 Mo isotopes with bosons number 5 , 4 and 5 respectively. The" reduced transition probability B(E2)" of these neuclei are calculated and compared with the experimental data . The ratio of the excitation energies of the 41+ to 21+ states ( R4/2) are also calculated . The calculated and experimental (R4/2) values showed that the 90 – 94 Mo nuclei have the vibrational dynamical symmetry U(5). Good agreement was found from comparison between the calculated energy states and electric quadruple probabilities B(E2) transition of the 90–94Mo isotopes with the experimental data .

scholarly journals The ultra-violet spectrum of magnesium hydride. 1.—The band at λ 2430

1929 ◽  
Vol 122 (790) ◽  
pp. 442-455 ◽  
Keyword(s):  
Fine Structure ◽  
General Structure ◽  
Energy Levels ◽  
Visible Region ◽  
Ultra Violet ◽  
Present Theory ◽  
Magnesium Hydride ◽  
Electronic Energy ◽  
Band Spectra ◽  
Electronic Energy Levels

The system of bands in the visible region of the emission spectrum of magnesium hydride is now well known. The bands with heads at λλ 5622, 5211, 4845 were first measured by Prof. A. Fowler, who arranged many of the strongest lines in empirical series for identification with absorption lines in the spectra of sun-spots. Later, Heurlinger rearranged these series in the now familiar form of P, Q and R branches, and considered them, with the OH group, as typical of doublet systems in his classification of the fine structure of bands. More recently, W. W. Watson and P. Rudnick have remeasured these bands, using the second order of a 21-foot concave grating, and have carried out a further investigation of the fine structure in the light of the present theory of band spectra. Their detection of an isotope effect of the right order of magnitude, considered with the general structure of the system, and the experimental work on the production of the spectrum, seems conclusive in assigning these bands to the diatomic molecule MgH. The ultra-violet spectrum of magnesium hydride is not so well known. The band at λ 2430 and the series of double lines in the region λ 2940 to λ 3100, which were recorded by Prof. Fowler in 1909 as accompanying the group of bands in the visible region, appear to have undergone no further investigation. In view of the important part played by hydride band spectra in the correlation of molecular and atomic electronic energy levels, it was thought that a study of these features might prove of interest in yielding further information on the energy states of the MgH molecule. The present paper deals with observations on the band at λ 2430; details of an investigation of the other features of the ultra-violet spectrum will be given in a later communication.

scholarly journals Large Scale Shell Model Calculations of the Negative-Parity States Structure in 24Mg Nucleus

2021 ◽  
Vol 66 (4) ◽  
pp. 293
Author(s):  
A.A. Al-Sammarraie ◽  
F.A. Ahmed ◽  
A.A. Okhunov
Keyword(s):  
Shell Model ◽  
Large Scale ◽  
Transition Probabilities ◽  
Transition Probability ◽  
Energy Levels ◽  
Form Factors ◽  
Model Space ◽  
Negative Parity ◽  
Matrix Elements ◽  
Model Calculations

The negative-parity states of 24Mg nucleus are investigated within the shell model. We are based on the calculations of energy levels, total squared form factors, and transition probability using the p-sd-pf (PSDPF) Hamiltonian in a large model space (0 + 1) hW. The comparison between the experimental and theoretical states showed a good agreement within a truncated model space. The PSDPF-based calculations successfully reproduced the data on the total squared form factors and transition probabilities of the negative-parity states in 24Mg nucleus. These quantities depend on the one-body density matrix elements that are obtained from the PSDPF Hamiltonian. The wave functions of radial one-particle matrix elements calculated with the harmonic-oscillator potential are suitable to predict experimental data by changing the center-of-mass corrections.

scholarly journals The Temperature Dependence of Fundamental Photophysical Properties of [Eu(MeOH-d4)9]3+ Solvates and [Eu.DOTA(MeOH-d4)]- Complexes

2021 ◽  
Author(s):  
Nicolaj Kofod ◽  
Lea Gundorff Nielsen ◽  
Thomas Just Sørensen
Keyword(s):  
Transition Probabilities ◽  
Photophysical Properties ◽  
Transition Probability ◽  
Energy Levels ◽  
Emission Spectra ◽  
Lanthanide Ions ◽  
Quantum Yields ◽  
Luminescence Spectra ◽  
Absorption Cross ◽  
Apparent Lack

The trivalent lanthanide ions show optical transitions between energy levels within the 4f shell. All these transitions are formally forbidden according to the quantum mechanical selection rules used in molecular photophysics. Nevertheless, highly luminescent complexes can be achieved, and terbium(iii) and europium(iii) ions are particularly efficient emitters. This report started when an apparent lack of data in the literature led us to revisit the fundamental photophysics of europium(iii). The photophysical properties of two complexes – [Eu.DOTA(MeOH-d4)]- and [Eu(MeOH-d4)9]3+ – were investigated in deuterated methanol at five different temperatures. Absorption spectra showed decreased absorption cross sections as the temperature was increased. Luminescence spectra and time-resolved emission decay profiles showed a decrease in intensity and lifetime as a temperature was increased. Having corrected the emission spectra for the actual number of absorbed photons and differences in non-radiative pathways, the relative emission probability was revealed. These were found to increase with increasing temperature. The transition probability for luminescence was shown to increase with temperature, while the transition probability for light absorption decreased. The changes in transition probabilities were correlated to a change in the symmetry of the absorber or emitter, with an average increase in symmetry lowering absorption cross section and access to more asymmetric structures increasing the emission rate constant. Determining luminescence quantum yields and the Einstein coefficient for spontaneous emission allowed us to conclude that lowering symmetry increases both. Further, it was found that collisional self-quenching is an issue for lanthanide luminescence, when high concentrations are used. Finally, detailed analysis revealed results that show the so-called ‘Werts’ method’ for calculating radiative lifetimes and intrinsic quantum yields are based on assumption that does not hold for the two systems investigated here. We conclude that we are lacking a good theoretical description of the intraconfigurational f-f transition, and that there are still aspects of fundamental lanthanide photophysics to be explored.<br>

scholarly journals The ultra-violet spectrum of magnesium hydride.—II. The many-lined γ-system

1929 ◽  
Vol 125 (796) ◽  
pp. 157-179 ◽  
Keyword(s):  
Molecular Weight ◽  
Energy Levels ◽  
Visible Region ◽  
Ultra Violet ◽  
Magnesium Hydride ◽  
The Many ◽  
The One ◽  
Low Pressures

During the course of investigation of the bands at λλ 5622, 5211 and 4845, emitted by the magnesium arc in hydrogen at low pressures, Prof. A. Fowler observed that they were always accompanied by a further band at λ 2430 and by series of double lines in the region λ 2940 to λ 3100. These features of this spectrum seemed to merit further study in view of the important part played by the spectra of other molecules with 13 electrons (CN, BO, BeF, CO + , N 2 + ) in the classification of molecular energy levels. Further, MgH is one of the interesting series of hydrides (BeH, MgH, CaH, ZnH, CdH, HgH) which show a pair of excited P states, with doublet separation increasing with molecular weight, closely resembling the lowest 2 P state of the preceding monovalent atoms (Li, Na, K, Cu, Ag, Au). An account of an analysis of the band at λ 2430 was given in a previous paper; the present paper deals with the series of double lines. For convenience the system in the visible region is referred to as the α-system, the one represented by the band at λ 2430 as the β-system, and that about to be described as the γ-system.

scholarly journals On the theory of the catalysis of the ortho-para transformation by paramagnetic gases

1935 ◽  
Vol 150 (871) ◽  
pp. 520-533 ◽  
Keyword(s):  
Nuclear Spin ◽  
Transition Probability ◽  
Electronic Configuration ◽  
Statistical Weight ◽  
Quantum Numbers ◽  
Symmetry Properties ◽  
Two Factors ◽  
Paramagnetic Molecules ◽  
The One ◽  
The Magnetic Field

According to quantum statistics, there exists for a diatomic molecule containing similar atoms an important difference between states with even and uneven rotational quantum numbers j . These two kinds of states have different statistical weights in the ratio of (S + 1)/S or S/(S + 1) where S is the nuclear spin. Whether the states of larger statistical weight possess even or uneven values of j depends on the symmetry properties of the electronic configuration and on the nuclear statistics. The states with the larger weight are called the ortho-states, those with the smaller weight the para-states. Under normal conditions, the transition probability between ortho-and para-states is zero. There are, however, two ways of inducing an ortho-para transformation. The one consists in dissociating the molecules, after which the atoms will recombine at random. The other possibility is to introduce a perturbation which depends both on the spins and on the positions of the nuclei. Under such conditions a transition may take place for the following reason: the unperturbed eigenfunction can be written as a product of two factors Ψ = ψ ( q 1 , q 2 ) ψ (s 1 , s 2 ) depending respectively on the space-co-ordinates q and the spin-vectors s of the two nuclei. Now, in order that an ortho-para transition may take place, it is necessary that the symmetry properties with respect to a permutation of the nuclei shall be changed in both factors. A simultaneous transition in ψ( q 1 , q 2 ) and ψ(s 1 , s 2 ) can, however, only occur if the perturbation contains a term depending both on q and s. It is due to a perturbation of this kind that the ortho-para hydrogen transformation is catalysed by paramagnetic gases as was found by Farkas and Sachsse. The interaction between the magnetic field of the paramagnetic molecules and the magnetic moment of the H-nuclei depends on the nuclear spin and, as the field is inhomogeneous, it also involves the nuclear positions. The theory of this catalysis was given by Wigner.

Non-linear optics probes of ultra-violet energy levels of solids at high pressures

1994 ◽  
Author(s):  
William B. Daniels ◽  
M. Lipp ◽  
D. Strachan ◽  
C. Yoo ◽  
H. M. Zhang ◽  
...  
Keyword(s):  
High Pressures ◽  
Energy Levels ◽  
Ultra Violet ◽  
Linear Optics ◽  
Non Linear Optics ◽  
Non Linear

scholarly journals Extended Atomic Structure Calculations for W11+ and W13+

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 92
Author(s):  
Narendra Singh ◽  
Sunny Aggarwal ◽  
Man Mohan
Keyword(s):  
Transition Probability ◽  
Energy Levels ◽  
Ground Level ◽  
Fusion Plasmas ◽  
Excitation Energies ◽  
New Energy ◽  
Atomic Structure Calculations ◽  
Structure Calculations ◽  
Theoretical Results ◽  
Good Agreement

We report an extensive and elaborate theoretical study of atomic properties for Pm-like and Eu-like Tungsten using Flexible Atomic Code (FAC). Excitation energies for 304 and 500 fine structure levels are presented respectively, for W11+ and W13+. Properties of the 4f-core-excited states are evaluated. Different sets of configurations are used and the discrepancies in identifications of the ground level are discussed. We evaluate transition wavelength, transition probability, oscillator strength, and collisional excitation cross section for various transitions. Comparisons are made between our calculated values and previously available results, and good agreement has been achieved. We have predicted some new energy levels and transition data where no other experimental or theoretical results are available. The present set of results should be useful in line identification and interpretation of spectra as well as in modelling of fusion plasmas.

ROTATIONAL WINGS OF RAMAN BANDS AND FREE ROTATION IN LIQUID OXYGEN, NITROGEN, AND METHANE

1952 ◽  
Vol 30 (2) ◽  
pp. 81-98 ◽  
Author(s):  
M. F. Crawford ◽  
H. L. Welsh ◽  
J. H. Harrold
Keyword(s):  
Raman Spectrum ◽  
Transition Probability ◽  
Energy Levels ◽  
Anisotropic Scattering ◽  
Rotational Energy ◽  
Rate Of Change ◽  
Liquid Oxygen ◽  
Discrete Structure ◽  
Anisotropic Part ◽  
Liquid Methane

Rotation-vibrational Raman bands have been observed in liquid oxygen, nitrogen, and methane, and in solid methane. In every case the Q branches associated with isotropic Raman scattering are sharp lines; but the Q branches and rotational wings associated with anisotropic scattering form broad continuous bands, with extent and intensity distribution consistent with free molecular rotation. The lack of discrete structure in the broad bands is attributed to a removal of the m degeneracy of the rotational energy levels in the intermolecular force fields. Removal of the m degeneracy broadens those transitions for which the transition probability depends on the anisotropic part of the rate of change of the polarizability, but not those for which J and m are unchanged and for which the transition probability depends only on the isotropic part. The Raman spectrum of liquid oxygen yields no evidence for O4 aggregates. The Raman spectrum of liquid methane displays all fundamental vibrations of the molecule and two overtones, with Raman shifts (in cm.−1): 1300, band (ν4); 1535, band (ν2); 2570, line, and 2600, band (2ν4); 2906, line (ν1); 3020, band (ν3); 3053, line (2ν2).

Conversion-electron and gamma–gamma directional correlation measurements in 134Ba

1990 ◽  
Vol 68 (12) ◽  
pp. 1479-1485 ◽  
Author(s):  
Bakhshish Chand ◽  
Jatinder Goswamy ◽  
Devinder Mehta ◽  
Nirmal Singh ◽  
P. N. Trehan
Keyword(s):  
Conversion Electron ◽  
Hpge Detector ◽  
Transition Probability ◽  
Energy Levels ◽  
Electron Spectrometer ◽  
Conversion Electrons ◽  
Conversion Coefficients ◽  
First Time ◽  
Rotor Model

Conversion electrons from the decay of 134Cs have been investigated using a mini-orange electron spectrometer. The electron intensities for the K-conversion of 242.7 keV and L, (M + N … ) conversion of 563.2, 795.9, 801.9, 1038.6, 1167.9, and 1365.2 keV transitions in 134Ba are being reported for the first time. The conversion-electron data have been further used to determine the conversion coefficients for various transitions in, 34Ba. Also, the gamma–gamma directional correlation measurements for seven cascades in 134Ba have been carried out using a HPGe–HPGe detector coincidence setup. The multipole admixtures for the 475.3, 563.2, 569.3, 795.9, 801.9, 1038.6, and 1365.2 keV transitions have been deduced from these measurements. A multipole admixture of M1 + 37% E2 has been obtained for the 1038.6 keV transition in 134Ba. The reduced transition probability ratios for the transitions de-exciting second 2+ and 3+ energy levels in 134Ba have been calculated and compared with the values predicted by the triaxial rotor model for γ = 28.5°. This indicates the softness of the, 134Ba nucleus toward γ deformation.

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