Energy Dependence Of Resonance Research Articles

Estimation of the emission altitude of pulsating aurora using the five-wavelength photometer

Using a ground-based five-wavelength photometer, which has been operative in Tromsø, Norway since February 2017, we have statistically analyzed the lifetime of O(1S) to reveal the emission altitude of pulsating aurora (PsA). For the statistics, we have extracted intervals of PsA using an EMCCD all-sky imager on 37 nights during 3 months from January to March, 2018. By performing a cross-correlation analysis between the time-series of 427.8 nm (N2+ first negative band) and 557.7 nm oxygen emissions, we derived the distribution of the lifetime of O(1S). The mean of the lifetime is 0.67 s and the mode is around 0.7 s. We estimated the emission altitude of PsA using the lifetime of O(1S) and then carried out a case study, in which we compared the temporal variations of the emission altitude with the peak height of E region ionization obtained from the simultaneous observation of the EISCAT UHF radar. We confirmed an overall agreement between the two parameters, indicating the feasibility of using the current method for estimating the energy of precipitating electrons causing PsA. In addition, we have derived the statistical characteristics of the emission altitude of PsA. The result shows that the emission altitude becomes lower in the morning side than in the midnight sector, which indicates that the energy of PsA electrons is higher in the later MLT sector. Especially, there is a decrease of the emission altitude at around 06 MLT. However, the model calculation infers that the energy of cyclotron resonance between magnetospheric electrons and whistler-mode chorus waves does not change so much depending on MLT. This implies that the observed change of the emission altitude cannot be explained only by the MLT dependence of resonance energy.

Many-Body Physics of Single and Double Spin-Flip Excitations in NiO.

Understanding many-body physics of elementary excitations has advanced our control over material properties. Here, we study spin-flip excitations in NiO using Ni L_{3}-edge resonant inelastic x-ray scattering (RIXS) and present a strikingly different resonant energy behavior between single and double spin-flip excitations. Comparing our results with single-site full-multiplet ligand field theory calculations we find that the spectral weight of the double-magnon excitations originates primarily from the double spin-flip transition of the quadrupolar RIXS process within a single magnetic site. Quadrupolar spin-flip processes are among the least studied excitations, despite being important for multiferroic or spin-nematic materials due to their difficult detection. We identify intermediate state multiplets and intra-atomic core-valence exchange interactions as the key many-body factors determining the fate of such excitations. RIXS resonant energy dependence can act as a convincing proof of existence of nondipolar higher-ranked magnetic orders in systems for which, only theoretical predictions are available.

Doping evolution of the charge excitations and electron correlations in electron-doped superconducting La2\u2212xCexCuO4

Electron correlations play a dominant role in the charge dynamics of the cuprates. We use resonant inelastic X-ray scattering (RIXS) to track the doping dependence of the collective charge excitations in electron doped La{}_{2-x}Ce{}_{x}CuO{}_{4} (LCCO). From the resonant energy dependence and the out-of-plane momentum dependence, the charge excitations are identified as three-dimensional (3D) plasmons, which reflect the nature of the electronic structure and Coulomb repulsion on both short and long lengthscales. With increasing electron doping, the plasmon excitations increase monotonically in energy, a consequence of the electron correlation effect on electron structure near the Fermi surface (FS). Importantly, the plasmon excitations evolve from a broad feature into a well-defined peak with much increased life time, revealing the evolution of the electrons from incoherent states to coherent quasi-particles near the FS. Such evolution marks the reduction of the short-range electronic correlation, and thus the softening of the Mottness of the system with increasing electron doping.

Formation of Formic Acid, Formaldehyde, and Carbon Dioxide by Electron-Induced Chemistry in Ices of Water and Carbon Monoxide

The processing of cryogenic ices consisting of water and carbon monoxide by different types of radiation is known to lead to the formation of carbon dioxide, formic acid, formaldehyde, and also methanol. In this study, we have investigated these reactions upon electron irradiation with energies between 2 and 20 eV, an energy range typically found in secondary electrons. This is the first time that the reactions have been monitored with a sufficiently fine step width in energy to resolve and identify the primary electron–molecule interactions leading to the specific products. This enables us to elucidate reaction mechanisms by linking these primary electron–molecule interactions to final products. In these reactions, HCO• and HOCO• radicals are key intermediates. Our results show that the HCO• intermediate predominantly leads to formaldehyde, while HOCO• is intermediate to the formation of formic acid. Noticeably, the formation of both formaldehyde and formic acid is enhanced within characteristic energy ranges by resonant electron attachment processes. In contrast, the reactions leading to carbon dioxide show no resonant energy dependence but can be traced back to nonresonant neutral dissociation processes. This reveals that carbon dioxide is linked to neither of these two intermediates. This is in contrast to prior experimental studies, which have proposed that carbon dioxide is formed by loss of a H• radical from HOCO•. However, our results confirm theoretical studies that have predicted that carbon dioxide formation from HOCO• is not very efficient, because HOCO• presents an energetic well and quickly loses any excess energy it might have in an ice matrix. Instead, we provide evidence that the primary electron–molecule interaction leading to the formation of carbon dioxide in cryogenic ices of water and carbon monoxide is the neutral dissociation of water into O atoms and H2. The so-formed O atoms then react directly with carbon monoxide to yield carbon dioxide.

Resonant electron-lattice cooling in graphene

Controlling energy flows in solids through switchable electron-lattice cooling can grant access to a range of interesting and potentially useful energy transport phenomena. Here we discuss a unique switchable electron-lattice cooling mechanism arising in graphene due to phonon emission mediated by resonant scattering on defects in crystal lattice, which displays interesting analogy to the Purcell effect in optics. This mechanism strongly enhances the electron-phonon cooling rate, since non-equilibrium carriers in the presence of momentum recoil due to disorder can access a larger phonon phase space and emit phonons more effciently. Resonant energy dependence of phonon emission translates into gate-tunable cooling rates, exhibiting giant enhancement of cooling occurring when the carrier energy is aligned with the electron resonance of the defect.

Stability of Weyl metals under impurity scattering

We investigate the effects of bulk impurities on the electronic spectrum of Weyl semimetals, a recently identified class of Dirac-type materials. Using a $T$-matrix approach, we study resonant scattering due to a localized impurity in tight binding versions of the continuum models recently discussed by Burkov, Hook, and Balents, describing perturbed four-component Dirac fermions in the vicinity of a critical point. The impurity potential is described by a strength $g$ as well as a matrix structure $\Lambda$. Unlike the case in d-wave superconductors, where a zero energy resonance can always be induced by varying the impurity scalar and/or magnetic impurity strength, we find that for certain types of impurity ($\Lambda$), the Weyl node is protected, and that a scalar impurity will induce an intragap resonance over a wide range of scattering strength. A general framework is developed to address this question, as well as to determine the dependence of resonance energy on the impurity strength.

Single-spin physics: experimental trends and their origin

The review of experimental trends in the physics of single-spin processes and their origin in the framework of an effective color field model is presented. A global analysis of polarization data for a large set of different reactions in h-h, h-A, A-A and lepton-A collisions is performed. In particular, the single-spin asymmetry, the polarization of hyperons and antihyperons are analyzed. The analysis revealed many common trends in the behavior of the experimental data, depending on the kinematic variables, the quark structure of hadrons and the mass of the colliding ions. The origin of large single-spin effects can be attributed to the influence of force such as the Stern-Gerlach-like one in a chromomagnetic field and to the Thomas precession in chromoelectric component of the Effective Color Field (ECF). Precession of the spin of the quarks in a chromomagnetic field is a major cause of the oscillation of the polarization as a function of kinematic variables. Focusing of quarks in the ECF leads to the resonant energy dependence of the single-spin observables. The predictions of large single-spin effects for the different reactions are presented, in particular, the expected oscillations of SSA and polarization, as well as change their sign at RHIC energies due to the growth of ECF with increasing reaction energy or the atomic weight of the ions. The Quark Counting Rules determine the sign and magnitude of the ECF.

ABC effect in double-pionic nuclear fusion and a pn resonance as its possible origin

A short overview over the ABC phenomenon is given, which is known since 50 years without any satisfactory explanation. On the basis of new exclusive and kinematically complete data obtained with the WASA detector at COSY we show that this phenomenon is linked with a resonant energy dependence in the total cross section of isoscalar double-pionic fusion processes. This resonance structure is connected with the baryon-baryon system, in particular with the pn and ΔΔ systems, however, has a mass, which is 90 MeV below the nominal ΔΔ threshold and a width of only 70 MeV, i.e., five times smaller than expected from a conventional t-channel ΔΔ scenario.

Study of Few-Body Problems at WASA — the ABC Phenomenon

A short overview over the ongoing few-body program at WASA@COSY is given with special emphasis on the ABC phenomenon, which is known since 50 years without having found a consistent explanation. We show that this phenomenon is linked with a resonant energy dependence in the total cross section of isoscalar double-pionic fusion processes. This resonance structure is connected with the baryon-baryon system, in particular with the pn and ∆∆ systems, however, possesses a mass, which is 90 MeV below the nominal ∆∆ threshold and has a width of only 50 MeV, i. e., five times smaller than expected from a conventional t-channel ∆∆ process.

DEPENDENCE OF MAGNETIC SUSCEPTIBILITY ON THE NEXT NEAREST HOPPING TERM FOR HIGH TC CUPRATES

In view of increasing emphasis on the use of next-nearest hopping t' term in the t - J Hamiltonian, we examine its effect on the spin susceptibility and its correlation with the structure of phase diagram. We find from this study that the resonance peak of spin susceptibility rapidly decreases with hole concentration in the overdoped region at which the spin singlet pairing order diminishes. It is shown that the doping dependence of resonance energy in both underdoped and overdoped regions is in agreement with observations.

Hadron resonances and phase threshold in heavy ion collisions

We show that a measurement of the reaction energy ({radical}(s)) dependence of relative hadron resonance yields in heavy ion collisions can be used to study the phase structure of the dense strongly interacting matter created in these collisions and investigate the origin of the trends observed in the excitation functions of certain soft hadronic observables. We show that the presence of chemical nonequilibrium in light quark abundance imparts a characteristic signature on the energy dependence of resonance yields that differs considerably from what is expected in the equilibrium picture.

Incident photon energy dependence of the resonant x-ray magnetic scattering cross section of a samarium film

Resonant x-ray magnetic scattering is widely used as an element selective probe of magnetism in solids. The present work deals with a different, less frequently addressed aspect: the electronic shell selectivity. Due to the complexity of the atomic effects inherent to the resonant process and at the origin of the electronic shell selectivity, the data are generally considered on a qualitative basis. Here, we try to extend the arguments to a semiquantitative level. We show, through a detailed spectroscopic study of the resonance at the ${L}_{2}$ and ${L}_{3}$ edges of samarium in a single-crystal epitaxial film, how the exploitation of the atomic effects can lead to a deeper understanding of long-range magnetic order in this material. At the ${L}_{2,3}$ edges of rare earths, dipole resonances carry information on the polarization of the $5d$ band, whereas quadrupole resonances reflect the polarization of the $4f$ shell. The narrow width of the $4f$ band permits the interpretation of the quadrupole resonance below the ${L}_{3}$ edge using atomic considerations. A systematic study of the dependence of the $4f$ quadrupole resonance on wave-vector transfer shows that, within our resolution, the magnitude of the $4f$ moments in samarium is independent of the local environment (cubic or hexagonal). On the other hand, the energy dependence of the dipole resonance at and above the ${L}_{2}$ and ${L}_{3}$ absorption edges shows two maxima and is interpreted in the framework of an extended density of $5d$ states. Finally, the relative temperature dependences of the dipole and quadrupole resonances sheds light upon the respective contributions of the $4f$ and $5d$ levels to the long-range magnetic order in samarium.

Resonant energy dependence of the hyperpolarizability β: On the possibility of double resonance enhancement

The dependence of the first molecular hyperpolarizability on the energy of the transition to the first excited state is examined under the assumptions of the two-level model of Oudar and Chemla. It is found that the resonance enhancement term is not maximized when λmax lies between the fundamental wavelength and its harmonic, contrary to frequency assertion. It is also found that the explicit λmax dependence of β is much smaller than the implicit dependence. These two facts imply that it is indeed desirable for a nonlinear chromophore’s λmax to lie to the red of a laser’s second harmonic, but not because of double resonance enhancement.

Role of the Delta (1232) in the ( gamma,p) reaction.

The magnetic Born and intermediate-..delta.. contributions to the (..gamma..,p) reaction are calculated for /sup 4/He and /sup 16/O targets, within a framework which includes pion rescattering and proton distortions. The results are discussed in light of experimental data, which show no obvious resonant energy dependence for these nuclei. The calculations are also compared to several published theoretical approaches, which disagree with each other regarding the importance of the intermediate-..delta.. contribution to the (..gamma..,p) reaction at intermediate energies.

Neutron-proton final state interaction in the 3H( 3He, pα)n reaction at low bombarding energies

The 3H( 3He, pα)n reaction has been studied in a kinematically complete experiment at 3He bombarding energies between 0.31 and 2.80 MeV in order to detect a possible resonant energy dependence of the spin singlet ( T = 1) neutron-proton final state interaction (FSI). The data in the region of low n-p relative energies have been analyzed in terms of the Watson-Migdal formalism. Only a slight relative increase of the 1S 0 n-p FSI is observed with increasing bombarding energy. This result is not easily related to the strong isospin violations found in the two-body reaction 3H( 3He, d) 4He at similar 3He energies.