Low-lying Excited Levels Research Articles

Nuclear Data Sheets for A=30

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 30F, 30Ne, 30Na, 30Mg, 30Al, 30Si, 30P, 30S, 30Cl, and 30Ar. The recommended values for the level energies and their percentage decay modes, level lifetimes, γ energies, γ branching ratios, transition probabilities, etc. are presented. Among these nuclides, 30F is unobserved and most likely particle unbound. Additional experimental data are required for firm spin-parity assignments of the low-lying excited levels of 30Ne. The most well studied nuclide is 30Si followed by 30P. The data for the most proton-rich nuclide 30Ar are presented following the recent work of 2018Xu04 and 2015Mu13. This evaluation for A=30 supersedes the previous one, 2010Ba29.

The M1 transitions and visible spectra of W13+ ion

The theoretical visible transitions and spectra of W13+ ion from the Electron Beam Ion Trap are investigated by constructing and solving a collisional-radiative model (CRM) within the Quasi-Steady-State approximation. The necessary atomic data for constructing the CRM have been calculated using the relativistic configuration interaction (RCI) method and distorted wave approximation. The present results are in reasonable agreement with the available experimental observations and theoretical calculations. The relative intensities of the M1 transitions between the ground and low-lying excited fine-structure levels have been found to strongly depend on the electron density from ne=109 cm−3 to ne=1012 cm−3, which might be useful for the future diagnosis of the electron density of the plasma.

Synchrotron-based rotation-vibration spectroscopy of imidazole

We report the observation of the far-infrared absorption spectra of the ν21, ν20, ν19, ν18 and ν17 bands of imidazole in the 480–840 cm−1 range, taken at the Canadian Light Source using synchrotron radiation. The ν21, ν18 and ν17 bands were rotationally assigned and analyzed. Observations of the ν20 and ν19 bands were limited to their dense, unresolved Q branches. The analysis provided accurate origins for all five bands, and a first rotational characterization of the ν18 and ν17 levels, as well as a global fit that includes data from recent microwave experiments on the ground vibrational state and low-lying excited vibrational levels (Guiliano et al., 2019; Arenas et al., 2021).

Optical spectroscopy study of KDy(WO4)2: Crystal-field levels of Dy3+ and the Jahn–Teller transition

Transmission spectra of a double potassium-dysprosium tungstate KDy(WO4)2 single crystal in the region of intermultiplet transitions of the Dy3+ ion and the Raman spectra of light scattering on the electronic levels of the 6H15/2 ground multiplet of Dy3+ are studied in a wide temperature range. The energy scheme for the crystal-field (CF) levels of Dy3+ in KDy(WO4)2 is created. The phase transition at the temperature 6.3 K is accompanied by the lowering of the energy of the ground Dy3+ CF state, which is evidenced by both the transmission and Raman spectroscopies. Splitting of the low-lying (∼13 cm–1) first excited CF level of the Dy3+ ion indicates the simultaneous structural phase transition. The role of Davydov interaction is discussed.

Elimination of degeneracy in the γ -unstable Bohr Hamiltonian in the presence of an extended sextic potential

In this paper, the $\ensuremath{\gamma}$-unstable Bohr Hamiltonian is studied in the presence of an extended sextic potential. It is expected that in this situation, we reach some degenerate levels in the energy spectrum, but we are interested in a case in which there is no degeneracy between those levels. This goal can be achieved by including the effects of an interaction made by the Casimir operator of SO(3). When this term is involved in the $\ensuremath{\gamma}$-unstable Bohr Hamiltonian, the degeneracy will be removed. According to the new scheme of energy levels, after the elimination of degeneracy, some low-lying excited levels are introduced. Then we examine the results by reproducing the experimental data of some isotopes for energy levels and $E2$ electromagnetic transitions.

Comparative investigation of the emission characteristics between 6.78-MHz radio-frequency and direct-current glow discharge plasmas for atomic emission spectrometry

This paper focused on the characteristics of emission spectra excited by a Grimm-style glow discharge plasma source in a 6.78-MHz radio-frequency (RF) power mode, in comparison to a conventional direct-current (DC) power mode. For this purpose, Boltzmann plots for atomic emission lines of iron were analyzed in detail, when the RF forward power and argon pressure in the discharge chamber were selected as the experimental parameters. The Boltzmann plot for low-lying excited levels of iron atom (3.4–4.8 eV) was on a linear relationship to provide an excitation temperature, whereas emission lines having larger excitation energies (more than 5 eV) generally deviated upwards from the linear relation. Any systematic dependence on the spin multiplicity was not found among the high-lying excited levels in the Boltzmann plot. The reason for the phenomenon was considered as follows: (1) the excitation for the low-lying emission lines would be caused by a dominant thermal collision process and (2) any non-thermal process also contributed to excitations for the high-lying emission lines to cause their over-population as a whole. The resultant excitation temperature was obtained in a narrow range of 3400–3600 K, which was hardly affected by the discharge power and the argon pressure, and further, the excitation temperature was very similar to that of a DC plasma that we had already reported. This result suggested that the glow discharge plasma could be supported by a self-stabilized negative glow region, where the kinetic energy distribution of the particles would be changed to a lesser extent as far as a stable discharge could be maintained.

Emission characteristics of 6.78-MHz radio-frequency glow discharge plasma in a pulsed mode

This paper investigated Boltzmann plots for both atomic and ionic emission lines of iron in an argon glow discharge plasma driven by 6.78-MHz radio-frequency (RF) voltage in a pulsed operation, in order to discuss how the excitation/ionization process was affected by the pulsation. For this purpose, a pulse frequency as well as a duty ratio of the pulsed RF voltage was selected as the experimenter parameters. A Grimm-style radiation source was employed at a forward RF power of 70W and at an argon pressures of 670Pa. The Boltzmann plot for low-lying excited levels of iron atom was on a linear relationship, which was probably attributed to thermal collisions with ultimate electrons in the negative glow region; in this case, the excitation temperature was obtained in a narrow range of 3300–3400K, which was hardly affected by the duty ratio as well as the pulse frequency of the pulsed RF glow discharge plasma. This observation suggested that the RF plasma could be supported by a self-stabilized negative glow region, where the kinetic energy distribution of the electrons would be changed to a lesser extent. Additional non-thermal excitation processes, such as a Penning-type collision and a charge-transfer collision, led to deviations (overpopulation) of particular energy levels of iron atom or iron ion from the normal Boltzmann distribution. However, their contributions to the overall excitation/ionization were not altered so greatly, when the pulse frequency or the duty ratio was varied in the pulsed RF glow discharge plasma.

Interference stabilization of atoms in a strong laser field for obtaining inversion and lasing in the visible and VUV frequency ranges

The interference stabilization of Rydberg atoms in strong laser fields is proposed for producing a plasma channel with the inverse population. Inversion between a group of Rydberg levels and low-lying excited levels and the ground state permits amplification and lasing in the IR, visible, and VUV frequency ranges. The lasing and light amplification processes in the plasma channel are analyzed using rate equations and the efficiency of this method is compared with that in the usual method for high harmonic generation during rescattering of electrons by a parent ion.

Comparative study on contribution of charge-transfer collision to excitations of iron ion between argon radio-frequency inductively-coupled plasma and nitrogen microwave induced plasma

This paper describes an ionization/excitation phenomenon of singly-ionized iron occurring in an Okamoto-cavity microwave induced plasma (MIP) as well as an argon radio-frequency inductively-coupled plasma (ICP), by comparing the Boltzmann distribution among iron ionic lines (Fe II) having a wide range of the excitation energy from 4.76 to 9.01eV. It indicated in both the plasmas that plots of Fe II lines having lower excitation energies (4.76 to 5.88eV) were fitted on each linear relationship, implying that their excitations were caused by a dominant thermal process such as collision with energetic electron. However, Fe II lines having higher excitation energies (more than 7.55eV) had a different behavior from each other. In the ICP, Boltzmann plots of Fe II lines assigned to the higher excited levels also followed the normal Boltzmann relationship among the low-lying excited levels, even including a deviation from it in particular excited levels having an excitation energy of ca. 7.8eV. This deviation can be attributed to a charge-transfer collision with argon ion, which results in the overpopulation of these excited levels, but the contribution is small. On the other hand, the distribution of the high-lying excited levels was non-thermal in the Okamoto-cavity MIP, which did not follow the normal Boltzmann relationship among the low-lying excited levels. A probable reason for the non-thermal characteristics in the MIP is that a charge-transfer collision with nitrogen molecule ion having many vibrational/rotational levels could work for populating the 3d64p (3d54s4p) excited levels of iron ion broadly over an energy range of 7.6–9.0eV, while collisional excitation by energetic electron would occur insufficiently to excite these high-energy levels.

Relaxation dynamics in a Fe7nanomagnet

We investigate the phonon-induced relaxation dynamics in the Fe${}_{7}$ magnetic molecule, which is made of two Fe${}^{3+}$ triangles bridged together by a central Fe${}^{3+}$ ion. The competition between different antiferromagnetic exchange interactions leads to a low-spin ground state multiplet with a complex pattern of low-lying excited levels. We theoretically investigate the decay of the time correlation function of molecular observables, such as the cluster magnetization, due to the spin-phonon interaction. We find that more than one time contributes to the decay of the molecular magnetization. The relaxation dynamics is probed by measurements of the nuclear spin-lattice relaxation rate $1/{T}_{1}$. The interpretation of these measurements allows the determination of the magnetoelastic coupling strength and to set the scale factor of the relaxation dynamics time scales. In our theoretical interpretation of $1/{T}_{1}$ data we also take into account the wipeout effect at low temperatures.

Excitation Processes in Introduction of Bias Current to a Radio-frequency Glow Discharge Plasma Evaluated from Boltzmann Plots of Iron Atomic and Ionic Spectral Lines

A DC current, which was driven by the self-bias voltage, could be conducted in a radio-frequency-powered glow discharge plasma by connecting a low-pass filter circuit and a load resistor with the discharge tube. This current enhanced the intensity of emission spectra from the plasma largely. The intensities of iron atomic lines increased 35 - 50 times, whereas the sputtering rate was not changed by the current introduction. Boltzmann plots for iron atomic (Fe I) and ionic lines (Fe II) were investigated when the bias current was conducted, so that the excitation process relating to the intensity increase could be clarified. While the excitation temperature of the Fe I lines was slightly changed (3000 - 3600 K), that of the Fe II lines was drastically reduced from 7600 to 4300 K, which was close to the temperature of the Fe I lines at higher bias currents. Therefore, the plasma was changed towards an LTE condition so that both the Fe I and the Fe II lines could be excited through a common major process. The bias-current enhanced the density of electrons enabling low-lying excited energy levels (3 - 5 eV) of iron atom/ion to be much more populated, and they became the major colliding partners for the excitation of these iron species.

Linking [FeIII3] triangles with “double-headed”phenolic oximes

The use of "double-headed" phenolic oximes produces a trigonal antiprismatic [Fe(III)(3)](2) cluster with an "internal cavity" filled with an additional Fe(3+) ion. Magnetic measurements reveal that the competition between different exchange interactions leads to a low-spin ground multiplet weakly separated in energy from a complex pattern of low-lying excited levels.

Lattice versus continuum theory of the periodic Heisenberg chain

We consider the detailed structure of low energy excitations in the periodic spin-1/2 XXZ Heisenberg chain. By performing a perturbative calculation of the non-linear corrections to the Gaussian model, we determine the exact coefficients of asymptotic expansions in inverse powers of the system length N for a large number of low-lying excited energy levels. This allows us to calculate eigenenergies of the lattice model up to order order N^-4, without having to solve the Bethe Ansatz equations. At the same time, it is possible to express the exact eigenstates of the lattice model in terms of bosonic modes.

Crossover from bound to free states in plasmas

A self-consistent joint description of free and weakly bound electron states in strongly coupled plasmas is presented. The existence of two problems is emphasized. The first one is a well-known restriction of the number of atomic excited states. Another one is a description of the smooth crossover from bound pair electron–ion excited states to collective excitations of free electrons. The fluctuation approach is developed to study the spectrum domain intermediate between low-lying excited atoms and free electron continuous energy levels. The molecular dynamics method is applied to study the plasma model since the method is able to distinguish all kinds of fluctuations. The electron–ion interaction is described by the temperature-independent cut-off Coulomb potential. The diagnostics of pair electron–ion fluctuations is developed. The concept of pair fluctuations elucidates the smooth vanishing of atomic states near the ionization limit. The approach suggested removes the artificial break of the electron state density at the ionization limit: atomic state density divergent at the negative energy side and free electron state density starting from zero density at the positive energy side.

Spectroscopy of the odd-oddfp-shell nucleusSc52from secondary fragmentation

The odd-odd fp-shell nucleus $^{52}\mathrm{Sc}$ was investigated using in-beam \ensuremath{\gamma}-ray spectroscopy following secondary fragmentation of a $^{55}\mathrm{V}$ and $^{57}\mathrm{Cr}$ cocktail beam. Aside from the known \ensuremath{\gamma}-ray transition at 674(5) keV, a new decay at ${E}_{\ensuremath{\gamma}}=212(3)$ keV was observed. It is attributed to the depopulation of a low-lying excited level. This new state is discussed in the framework of shell-model calculations with the GXPF1, GXPF1A, and KB3G effective interactions. These calculations are found to be fairly robust for the low-lying level scheme of $^{52}\mathrm{Sc}$ irrespective of the choice of the effective interaction. In addition, the frequency of spin values predicted by the shell model is successfully modeled by a spin distribution formulated in a statistical approach with an empirical, energy-independent spin-cutoff parameter.

New gamma transitions in 193Ir from the beta decay of 193Os

The population and the mode of decay of the low-lying excited levels of 193Ir have been investigated by single and gg coincidence spectroscopy using 192Os enriched to 99% and several HPGe detectors. From singles spectra analysis the energies of 71 gamma rays have been determined with a better overall precision than previously, 17 of them for the first time. The energies at 1043.244(15) and 1316.628(18)keV , observed for the first time in this work, as well as some preliminary coincidence relationships, suggest that the end point energy Qbmax(»1.14MeV) must be further investigated.

Dynamic magnetization process of the diluted antiferromagnet RbMn cMg 1- cF 3 in pulse field up to [formula omitted

In the context of quantum spin dynamics of a two-level system, we study the dynamic magnetization process of dimerized Mn 2+-Mn 2+ pairs in the diluted antiferromagnet RbMn c Mg 1- c F 3. Measurements have been performed up to 55 T and lower temperature down to 0.1 K . Magnetization anomalies are associated with successive large and small magnetization steps at specific fields with regular interval. Main steps occur at equally spaced level-crossing fields B n (1⩽ n⩽5) with a separation of ΔB=6.4 T and subsidiary ones are classified into higher harmonics which fall just in between at the fields B n/2 (1⩽n⩽10) separated by ΔB/2,B n/3 (1⩽n⩽15) separated by ΔB/3,B n/4 (1⩽n⩽20) separated by Δ B/4 and so on when the energy levels have separation with a simple ratio such as (1:1), (1:2), (1:3) and so on. At the lowest temperature, the observed d M/d B curve becomes simpler, suggesting important roles of low-lying excited levels, together with a spin-phonon coupling and a phonon bottleneck effect.

High-resolution Fourier-transform infrared spectroscopy of the ν2 fundamental band of thionyl fluoride, SOF2Electronic supplementary information (ESI) available: Tables S1 and S2. See http://www.rsc.org/suppdata/cp/b2/b210153j/

The high-resolution vibration–rotation spectrum of the ν2 fundamental band of gas-phase thionyl fluoride, SOF2, has been observed centred at 808 cm−1. Spectra were recorded in absorption using a Fourier-transform spectrometer with the sample of SOF2 held in a gas cell at a temperature of 294 K. In total, 1929 a- and c-type vibration–rotation transitions of the most abundant isotopomer, 32S16OF2, have been assigned and included in a least-squares fit. The least-squares analysis, performed using a standard semi-rigid rotor Hamiltonian, has yielded precise spectroscopic parameters for the v2=1 level. The analysis confirms the assignment of the band to excitation of the symmetric S–F stretching vibration. Additional, partially resolved features are attributed to the Q-branches of the ν2 fundamental band of 34S16OF2 and of ν2 difference bands from low-lying excited vibrational levels.

Gas heating in low-pressure microwave argon discharges.

Both an energy balance equation and a collisional-radiative model were developed in order to discover which process is responsible for gas heating in a low-pressure argon discharge. In this way, for a wide range of plasma conditions, the space-charge field contribution to gas heating was found to be negligible compared to that resulting from elastic collisional processes, although the value of the former is higher than the latter when calculating the absorbed power per electron. This is due to (1) the heating associated with the space-charge field only being effective in the plasma sheath, which is very close to the vessel inner wall. (2) The vessel temperature value at the external wall is taken as a boundary condition, as a result of which the space-charge field influence on gas heating is indirectly imposed on the model. The results of the collisional-radiative model take into account the influence of gas heating on the electron temperature and on the argon low-lying excited levels. Two different zones have been found. The first corresponds to low electron densities, in which the gas temperature remains constant, whereas in the second (high electron densities) the heating of the gas takes on great importance. These results compare well with experimental data.

Analysis of the electron paramagnetic resonance properties of the [2Fe-2S]1+ centers in molybdenum enzymes of the xanthine oxidase family: assignment of signals I and II.

Molybdoenzymes of the xanthine oxidase family contain two [2Fe-2S](1+,2+) clusters that are bound to the protein by very different cysteine motifs. In the X-ray crystal structure of Desulfovibrio gigas aldehyde oxidoreductase, the cluster ligated by a ferredoxin-type motif is close to the protein surface, whereas that ligated by an unusual cysteine motif is in contact with the molybdopterin [Romao, M. J., Archer, M., Moura, I., Moura, J. J. G., LeGall, J., Engh, R., Schneider, M., Hof, P., and Huber, R. (1995) Science 270, 1170-1176]. These two clusters display distinct electron paramagnetic resonance (EPR) signals: the less anisotropic one, called signal I, is generally similar to the g(av) approximately 1.96-type signals given by ferredoxins, whereas signal II often exhibits anomalous properties such as very large g values, broad lines, and very fast relaxation properties. A detailed comparison of the temperature dependence of the spin-lattice relaxation time and of the intensity of these signals in D. gigas aldehyde oxidoreductase and in milk xanthine oxidase strongly suggests that the peculiar EPR properties of signal II arise from the presence of low-lying excited levels reflecting significant double exchange interactions. The issue raised by the assignment of signals I and II to the two [2Fe-2S](1+) clusters was solved by using the EPR signal of the Mo(V) center as a probe. The temperature dependence of this signal could be quantitatively reproduced by assuming that the Mo(V) center is coupled to the cluster giving signal I in xanthine oxidase as well as in D. gigas aldehyde oxidoreductase. This demonstrates unambiguously that, in both enzymes, signal I arises from the center which is closest to the molybdenum cofactor.