Anomalous Absorption Research Articles

Causality conditions and signal propagation in bubbly water

Acoustic propagation through subsurface bubble clouds in the ocean can exhibit signal travel times with enormous variations depending on the acoustic signal frequency, bubble size distribution, and void fraction. Recent theories have predicted large variations in phase speeds and attenuation that have been largely validated for frequencies well below and well above bubble resonance. However, great care must be exercised when theoretically treating signal propagation at frequencies near resonance, termed the ‘‘Anomalous Absorption Regime’’ nearly 100 years ago in the pioneering work of Sommerfeld [A. Sommerfeld, Physik. Z. 8, 841 (1975)] while investigating aspects of electromagnetic causality. We will discuss similarities between acoustic propagation in bubbly media and electromagnetic propagation in the presence of a conducting medium. We show that the signal travel time is dependent on the behavior of the dispersion formula in the complex frequency plane and place limits on the range of validity of these formulas, leading naturally to the necessary modifications to the current dispersion formulas to bring them into compliance with causality. Finally, we present theoretical results for the velocity of signals for a representative environment of experimental work carried out at the Naval Research Laboratory. [Work supported by the ONR.]

Slow Propagation, Anomalous Absorption, and Total External Reflection of Surface Plasmon Polaritons in Nanolayer Systems

I predict that a nanoscopic, high-permittivity layer on the surface of a plasmonic metal can cause total external reflection of surface plasmon polaritons (SPPs). Such a layer can be used as a mirror in nanoplasmonics, in particular for resonators of nanolasers and spasers and can also be used in adiabatic nanooptics. I also show that the earlier predicted slow propagating SPP modes, especially those with negative refraction, are highly damped.

Influence of surfactant Ag on the structure of annealing Ni 70Co 30/Cu multilayers by X-ray reflection anomalous fine structure and X-ray absorption spectroscopy

We performed X-ray reflection anomalous fine structure and X-ray absorption spectroscopy measurements to investigate the influence of Ag as a surfactant on the annealing Ni 70Co 30/Cu multilayer for the first time. Interfacial intermixing and silver diffusion levels were quantified at the atomic level. During the deposition, a 6 Å thick intermixing region exists at the Cu/Ni 70Co 30 interface while the Ni 70Co 30/Cu interface is sharp for the un-doped and the Ag-doped multilayers. After 285 °C annealing, the two multilayers display different thermal behaviors. Severe diffusion occurs at the Cu/Ni 70Co 30 and Ni 70Co 30/Cu interfaces of the un-doped multilayer. However, of these the Ag-doped multilayer do not change significantly, indicating that the addition of silver can suppress interfacial intermixing after annealing. The Ag atoms in the Ag-doped multilayer have diffused into some parts of Ni 70Co 30 layer while do not exist at the interfaces during the deposition. After 285 °C annealing, the Ag atoms diffused into the whole Ni 70Co 30 layer as well as some parts of the Cu layer. The X-ray absorption spectroscopy measures show that Ni atoms and Cu atoms occupy the interfacial positions in the un-doped multilayer. The addition of silver also do not change the FCC lattice of Co, Ni and Cu, but decrease the amplitude of the Ni and the Co K edge EXAFS profiles, suggesting that Ag atoms do diffuse into the Ni 70Co 30 layer.

Search for 1 11–1 10 and 2 11–2 12 transitions of H 2CCO, H 2CCC and H 2CCCC in cosmic objects

Formaldehyde (H 2CO) is the first molecule observed in absorption against the cosmic microwave background (CMB) through its transition 1 11–1 10 at 4.829 GHz in several cosmic objects. The second line observed in a large number of cosmic objects is 2 11–2 20 transition at 21.59 GHz of cyclopropenylidene ( c-C 3H 2) in absorption against the CMB. The phenomenon of anomalous absorption can take place under rather peculiar conditions developed in a molecule generating the line. In the present investigation, for H 2CCO, H 2CCC and H 2CCCC in cool cosmic objects, we have accounted for kinetic temperature of 10, 20, 30 and 40 K. For each of these three molecules, we have taken 30 rotational energy levels connected by 66 radiative transitions and solved the set of statistical equilibrium equations coupled with equations of radiative transfer through iterative method. We found that relative values of collisional rates can produce anomalous absorption of transitions 1 11–1 10 and 2 11–2 12 in these molecules. Anomalous absorption of 1 11–1 10 and 2 11–2 12 transitions may help in the identification of molecules in cool cosmic objects.

Anesthetic Implication of Hemoglobin-M: A case report

Cyanosis in children is most often caused by pulmonary disease, or cyanotic heart disease but is rarely caused by hematological problems such as methemoglobinemia and sulfhemoglobinemia. Abnormal hemoglobins with a reduced oxygen affinity are an exceptionally uncommon cause of cyanosis in children. Hemoglobin-M (Hb-M) is rapidly auto-oxidized into the met-form resulting in the loss of its -binding ability. This hemoglobinopathy is inherited in an autosomal dominant pattern and is characterized by marked cyanosis. Hb-M affects the anesthetic management because of the anomalous absorption spectrum of Hb-M in standard pulse oximetry. Sufficient delivery should be maintained by keeping a high and intermittently checking the delivery state using arterial blood gas analysis. We reported our experience of the anesthetic management of a patient with hemoglobin M.

Emulsion chamber experiments; critical comments and future prospects

Emulsion chamber data give valuable information about particle production in the forward region of very high-energy nuclear interactions. Many characteristics of high-energy atmospheric families, observed by emulsion chambers, have not been fully described by simulations employing existing nuclear interaction models. Some of the events and the phenomena observed in emulsion chamber experiments have been considered to be unusual and new, never seen in lower energy accelerator experiments. We re-examine emulsion chamber data critically in order to get unbiased views of these unusual events and phenomena. It is shown that some of the previous interpretations need to be changed. We take up for the discussions scaling violation in C-jets, Centauro events, alignment of showers in high-energy families, hadrons of anomalous absorption in thick lead chambers. We will also discuss the results on the hybrid experiments of emulsion chamber and EAS-array.

XANES SPECTROSCOPY OF SULFUR IN EARTH MATERIALS

X-ray absorption near-edge structure (XANES) spectroscopy is the ideal non-destructive technique for characterizing and quantifying S species in compositionally complex natural materials such as silicate glasses and minerals, coals, asphalts and asphaltenes, kerogens and humic substances. Sulfur absorption edges represent the transition of S 1 s and 2 p core electrons to unoccupied antibonding orbitals at the bottom of the conduction band. Shifts in the position of the absorption-edge feature of S K - and L -edge XANES spectra constitute a chemical ruler for oxidation state of both inorganic and organic species of S; the S K edge shifts from 2469.5 eV for chalcopyrite (2− oxidation state) to 2482 eV for gypsum (6+). However, chemical state of S in Earth materials is most readily assigned by comparing the overall XANES profile with spectra for reference compounds. Sulfur XANES spectra are reviewed for pyrite, troilite, pyrrhotite and NiAs-type Co 0.923 S and Ni 0.923 S, niningerite (MgS), oldhamite (CaS), alabandite (MnS) and cubic FeS, and sphalerite and related phases, as well as for selected solid-solutions of the monosulfides. Sulfur XANES spectra for FeS, CoS, NiS, MgS, CaS, MnS and ZnS have been simulated by multiple scattering calculations. The S K -edge XANES of transition-metal-bearing monosulfides generally show anomalous absorption consistent with hybridization of the final S 3 p σ* antibonding states with empty 3 d orbitals on the metal atoms. Various applications of S K - and L -edge XANES fingerprinting are discussed, including speciation of inorganic S in basaltic glasses, lazurite and hauyne, identification of organic functional groups of S in coals, kerogens and humic substances extracted from subtropical soils and marine sediments, and the association of sulfated sugars with calcification of coral aragonite skeletons.

Structural properties of semiconductor nanostructures determined via X-ray anomalous diffraction (DAFS) and absorption (EXAFS)

We will report novel results on the structural properties of encapsulated semiconductor nanostructures obtained by an ultimate application of anomalous diffraction combined with ray absorption spectroscopy. We have been studying InAs/InP Quantum Sticks (QSs) and GaN/AlN Quantum Dots (QDs). Reciprocal space mapping and fixed-Q anomalous diffraction, mesured as a function of energy, in grazing incidence, gives access to the the partial structure factor of the embedded nanostructures (QSs or QDs), allowing to determine their size, strain and atomic composition. Quantitative analysis of the Grazing Incidence Diffraction Anomalous Fine Structure (GIDAFS) oscillations above the resonant edges, gives strain accommodation and coordination at a local atomic scale for the diffraction-selected isostrain region inside the nanostructures. On the other hand EXAFS measurements provide a comparison with the average atomic environment in the whole island. These methods have been applied succesfully both to InAs sticks and to the GaN dots.

Near-Field Intensity Correlations in Semicontinuous Metal-Dielectric Films

Spatial intensity correlation functions are obtained from near-field scanning optical microscope measurements of semicontinuous metal-dielectric films. The concentration of metal particles on a dielectric surface is varied over a wide range to control the scattering strength. At low and high metal coverages where scattering is weak, the intensity correlation functions exhibit oscillations in the direction of incident light due to excitation of propagating surface waves. In the intermediate regime of metal concentration, the oscillatory behavior is replaced by a monotonic decay as a result of strong scattering and anomalous absorption. Significant differences in the near-field intensity correlations between metallic and dielectric random systems are demonstrated.

Anomalous IR optical properties of aggregates of Pd nanoparticles induced through electrochemical cyclic voltammetry

IR optical properties of Pd nanoparticles with different size and aggregation state were studied in the current paper. The dispersed Pd nanoparticles ( P d n a ) stabilized with poly( N-vinylpyrrolidone) (PVP) were synthesized by the seeding growth method, in which the seeds were formed step by step through reducing H 2PdCl 4 with ethanol. The dispersed Pd nanoparticles of much large size ( P d n b ) were grown from the P d n a by keeping the colloid of P d n a undisturbed for 150 days at room temperature around 20 °C. The aggregates of P d n a ( P d n ag ) were prepared through an agglomeration process induced during a potential cyclic scanning between −0.25 V and 1.25 V for 20 min at a scan rate of 50 mV s −1. Scanning electron microscope (SEM) patterns confirmed such aggregation of P d n a . Fourier transform infrared (FTIR) spectroscopy together with CO adsorption as probe reaction was employed in studies of IR optical properties of the prepared Pd nanoparticles. The results demonstrated that CO adsorbed on P d n a films substrated on CaF 2 IR window or glassy carbon (GC) electrode yielded two strong IR absorption bands around 1970 cm −1 and 1910 cm −1, which were assigned to IR absorption of CO bonded on asymmetric and symmetric bridge sites, respectively. Similar IR bands were observed in spectra of CO adsorbed on P d n b films, except the IR bands were much weak, whereas CO adsorbed on P d n ag film produced an IR absorption band near 1906 cm −1, and an anomalous IR absorption band whose direction has been completely inverted around 1956 cm −1. The direction inversion of the IR band of CO bonded to asymmetric bridge sites on P d n ag was ascribed to the interaction between Pd nanoparticles inside the aggregates. Based on FTIR spectroscopic and cyclic voltammetric results, the aggregation mechanism of Pd nanoparticles from P d n a to P d n ag has been suggested that the agglomeration of Pd nanoparticles was driven by the alteration of electric field across electrode–electrolyte interface, when the PVP stabilizer was stripped via oxidation during cyclic voltammetry.

Anomalous Absorption of Radio Waves by Small-Scale Magnetic-Field-Aligned Irregularities

We study the anomalous absorption of radio waves by small-scale magnetic-field-aligned artificial irregularities taking into account the effect of such irregularities on the propagation of the excited Z -mode. It is shown that this process becomes significant if the transverse size of field-aligned irregularities is of the order of 0.1c/ω or greater, where ω is the radio wave frequency and c is the speed of light in vacuum.

An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

Abstract. When the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view of the not yet understood but complex relationship between electrostatic fluctuations and SEE, it is of interest to investigate experimentally whether a similar angular structure is present in the various spectral features of the SEE signals and to compare the results with radar and other observations of RF-pump-induced effects. To this end we describe a simple two-element radio interferometer designed to search for aspect angle dependence of SEE features. We present an example of the initial data produced by this system, and draw preliminary conclusions based on the example data.

Relaxation dynamics of the LH2 complex from a photosynthetic purple bacterium Thiorhodospira sibirica studied by the near-IR femtosecond pump-probe method

Photoinduced changes in the absorption spectrum of the LH2 (B800-830-850) complex from a Thiorhodospira sibirica (Trs. sibirica) bacterium are studied by the pump-probe method. The complex has the anomalous absorption spectrum exhibiting three bands in the near-IR region at 793, 826.5, and 846.5 nm. At room temperature, the excitation energy transfer from the B800, B830, and B859 bands was detected with the time constants τ1∼0.5 ps, τ2∼2.5 ps, and τ3 of the order of a few hundreds of picoseconds, respectively. A rapid energy transfer from the B830 band compared to energy transfer from the B850 band (τ2≪τ3) suggests that all the three bands belong to the same complex (i.e., that the LH2 complex from Trs. sibirica is homogeneous). A slower energy transfer (by three — five times) from the B830 band of the LH2 complex from Trs. sibirica compared to energy transfer from the B800 band of the LH2 complexes (B800-850 and especially B800-820) from other purple bacteria suggests that the electronic structures of ensembles of bacteriochlorophyll molecules in these complexes are substantially different.

Bernstein mode aided anomalous absorption of laser in a plasma

A laser propagating through a plasma, in the presence of an electron Bernstein wave, undergoes nonlinear mode coupling, producing a beat mode (ω+ω0, k+k0) where (ω0, k0) and (ω, k) are the frequency and wave number of the laser and the Bernstein mode. The oscillatory electron velocity associated with this beat mode couples with electron density perturbation due to the Bernstein wave to produce a nonlinear current at the laser frequency. When the beat mode is Landau damped on electrons, the nonlinear current at the laser frequency has an in-phase component with the laser field, giving rise to anomalous resistivity. The normalized anomalous resistivity is found to be maximum for q=∣k+k0∣νth∕(ω+ω0)≈0.8–0.9.

Solar Radiation Budget from the MRI Radiometers for Clear and Cloudy Air Columns within ARESE II

Abstract As an international collaborative research activity within the Japanese Cloud-Climate Study (JACCS) program, the authors participated in the second Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE II) using the Meteorological Research Institute (MRI) radiometers. This paper describes results of ARESE II, as well as specifications and calibration of the MRI radiometers. The solar radiation budget for 2 days of typical clear sky (27 February and 20 March 2000) and overcast sky (3 and 21 March 2000) has been analyzed using spatially collocated, total-band solar irradiances measured by the MRI pyranometers (Kipp & Zonen CM21). These were installed on a Twin Otter aircraft, and deployed at the ARM Southern Great Planes Central Facility site. On average, the clear-sky and overcast-sky air columns between the surface and the Twin Otter flight level of 7 km absorbed about 13% ± 2% and 20% ± 3%, respectively, of the total-band solar radiation incident on the column top. The measured solar radiation budgets agree well with those computed for models of clear and cloudy atmospheres. The present results indicate no evidence of anomalous solar absorption for either the clear- or cloudy-sky cases. It is suggested that about half of the observed absorption enhancement of 7% for the overcast-sky cases could be caused by the presence of larger water vapor, compared with the clear-sky cases, and that the other half could be caused by increased absorption within and above the rather low cloud layers.

KU1 and KS-4V quartz glass lenses for remote handling and diagnostic optical transmission systems

Radiation resistant KU1 and KS-4V quartz glasses are candidate ITER materials for remote handling and diagnostic optical transmission components such as windows, lenses, and optical fibres. 60Co gamma irradiations at different temperatures have been carried out to study ionizing radiation effects on refractive index, optical absorption, and the quality of lenses made from KU1 and KS-4V. No effect has been observed on the refractive index of KU1 for irradiations up to 100 MGy and temperatures up to 170 °C. Lenses made from both materials show acceptable quality before and after irradiation. Irradiation induced absorption is confined to the blue and UV region, however, KS-4V shows anomalous behaviour with irradiation temperature. In situ 1.8 MeV electron irradiations have been used to clarify this anomalous absorption.

Anomalous photoinduced absorption of conjugated polymer/fullerene mixtures at low temperatures and high frequencies

Light induced charge transfer from conjugated polymers and their oligomers to different electron acceptors, e.g. fullerenes or tetracyano-p-quinodimethane (TCNQ) derivatives has been studied extensively [1–5]. From time-resolved photoinduced absorption (PIA) studies it is well known that the charge-transfer process from a conjugated polymer to C60 or C60 derivatives takes place on an ultrafast time scale (<100 fs) [2]. On the other hand, the back electron transfer is remarkably slow; lifetimes on the order of milliseconds can be observed for the charge separated states in such systems. This very efficient charge separation has been utilized in polymeric photovoltaic devices [6–9]. Photoexcitation of conjugated polymers in liquid solutions or solid state films across the – ∗ energy gap produces a metastable triplet state by intersystem crossing from the excited singlet manifold [10,11]. These triplet states were identified by their dipole allowed T1–T2 transition, which exhibit a red shift with increasing chain length [10]. The lifetimes of these triplet states are on the order of 10–100 ms. In composite films of these polymers mixed with electron accepting molecules the triplet–triplet absorption is quenched due to a prior charge transfer. Absorption detected magnetic resonance (ADMR) experiments on films of pristine poly[2-methoxy-(5-2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) have shown that the origin of the photoinduced absorption in the range between 1.1 and 1.6 eV is due to excited triplet states (spin 1), whereas mixed films of MEH-PPV and C60 show in the same energetic region PIA

205Tl-NMR on Tl2SeO4

205Tl-NMR absorption lines in the Tl2SeO4 crystal have been measured below room temperature. We have observed the remarkable changes in the resonance position and line width of the 205Tl-NMR absorption line at TII–III = 97 K and TIII–IV = 74 K. It is also found that the large shift of the resonance position and with decreasing temperature the drastic increase of the line width of the 205Tl-NMR absorption line are observed even in the temperature range from 74 K to 97 K (phase III). Moreover below TII–III we have observed the anomalous 205Tl-NMR absorption lines with two peaks in both tails, although above TII–III the NMR absorption line is described by the single Gaussian curve. In addition, it is found that the positions of two peaks change even in the phase III. These results imply that the Tl2SeO4 crystal shows the structural incommensurate modulation in the phase III, as observed in many A2BX4 type crystals (A = K, Rb, Cs, NH4, N(CH3)4; B = Zn, Co, Se, S; X = Br, Cl, O).

Resonant nanocluster technology—from optical coding and high quality security features tobiochips

Metal clusters deposited on a substrate and positioned at a nanometric distance from awave-reflecting layer act as nanoresonators able to receive, store and transmit energywithin the visible and infrared range of the spectrum. Among the unique effects of thesemetal nanocluster assemblies are high local field enhancement and nanoscale resonantbehaviour driving optical absorption in the visible and infrared range of the spectrum.In these types of devices and sensors the precise nanometric assembly coupling the localfield surrounding a cluster is critical for allowing resonance with other elements interactingwith this field. In particular, the cluster–mirror distance or the cluster–fluorophore distancegives rise to a variety of enhancement phenomena (e.g. resonant-enhanced fluorescence,REF). Depending on the desired application this ‘resonance’ distance is tuned from 5 up to500 nm.High-throughput transducers using metal cluster resonance technology are based on surfaceenhancement of light absorption by metal clusters (surface-enhanced absorption, SEA).These devices can be used for detection of biorecognition binding as well as structuralchanges in nucleic acids, proteins or any polymer. The optical property made use of in theanalytical application of metal cluster films is so-called anomalous absorption. Anabsorbing film of clusters is positioned 10–400 nm from an electromagnetic wave-reflectinglayer. At a well-defined mirror–cluster distance the reflected electromagnetic field has thesame phase at the position of the absorbing cluster as the incident field. This feedbackmechanism strongly enhances the effective cluster absorption coefficient. These systems arecharacterized by a narrow reflection minimum whose spectral position shifts sensitivelywith interlayer thickness, because a given cluster–mirror distance and wavelength definesthe optimum phase.

Purification of electron-transferring flavoprotein from Megasphaera elsdenii and binding of additional FAD with an unusual absorption spectrum.

Electron-transferring flavoprotein (ETF), its redox partner flavoproteins, i.e., D-lactate dehydrogenase and butyryl-CoA dehydrogenase, and another well-known flavoprotein, flavodoxin, were purified from the same starting cell paste of an anaerobic bacterium, Megasphaera elsdenii. The purified ETF contained one mol FAD/mol ETF as the sole non-protein component and bound almost one mol of additional FAD. This preparation is a better subject for investigations of M. elsdenii ETF than the previously isolated ETF, which contains varying amounts of FAD and varying percentages of modified flavins such as 6-OH-FAD and 8-OH-FAD. The additionally bound FAD shows an anomalous absorption spectrum with strong absorption around 400 nm. This spectral change is not due to a chemical modification of the flavin ring because the flavin released by KBr or guanidine hydrochloride is normal FAD. It is also not due to unknown small molecules because the same spectrum appears when ETF is reconstituted from its guanidine-denatured subunits and FAD. A similar anomalous spectrum was observed for AMP-free pig ETF under acidic conditions, suggesting a common flavin environment between pig and M. elsdenii ETFs.