scholarly journals Fano interference in quantum resonances from angle-resolved elastic scattering

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Prerna Paliwal ◽  
Alexander Blech ◽  
Christiane P. Koch ◽  
Edvardas Narevicius
Keyword(s):  
Single Channel ◽  
Bound State ◽  
Model Description ◽  
Shape Resonance ◽  
Molecular Scattering ◽  
Metastable Helium ◽  
Line Shapes ◽  
Wave Interference ◽  
Theoretical Predictions ◽  
Continuum Of States

AbstractAsymmetric spectral line shapes are a hallmark of interference of a quasi-bound state with a continuum of states. Such line shapes are well known for multichannel systems, for example, in photoionization or Feshbach resonances in molecular scattering. On the other hand, in resonant single channel scattering, the signature of such interference may disappear due to the orthogonality of partial waves. Here, we show that probing the angular dependence of the cross section allows us to unveil asymmetric Fano profiles also in a single channel shape resonance. We observe a shift in the peak of the resonance profile in the elastic collisions between metastable helium and deuterium molecules with detection angle, in excellent agreement with theoretical predictions from full quantum scattering calculations. Using a model description for the partial wave interference, we can disentangle the resonant and background contributions and extract the relative phase responsible for the characteristic Fano-like profiles from our experimental measurements.

A hybrid model description of 13C(p,γ)14N capture reaction

2019 ◽  
Vol 28 (06) ◽  
pp. 1950038 ◽  
Author(s):  
Suprita Chakraborty ◽  
Avijit Mukherjee ◽  
Subinit Roy
Keyword(s):  
Excitation Function ◽  
Hybrid Model ◽  
Cross Sections ◽  
Bound State ◽  
Relative Energy ◽  
Model Description ◽  
Broad Resonance ◽  
Capture Reaction ◽  
Function Data ◽  
The Cross

The radiative capture reaction [Formula: see text] is analyzed using a hybrid model approach where the non-resonant component has been constructed employing the potential model with a folded M3Y potential. The one-level Breit–Wigner formula has been used to estimate the cross-sections of the resonant decays of dominant ([Formula: see text]) state of [Formula: see text]N at 8.06[Formula: see text]MeV. The contribution of the broad resonance at 8.77[Formula: see text]MeV ([Formula: see text]) has been dealt with differently. While Breit–Wigner formula has been used where the excitation function data exist, the [Formula: see text]-matrix prediction for the cross-section of decay to a bound state of [Formula: see text]N from the broad resonance has been used where excitation function data are not available. The single particle spectroscopic factors for ground and six excited states of [Formula: see text]N have been obtained from the fits. The resulting astrophysical [Formula: see text]-factor at zero relative energy is [Formula: see text][Formula: see text]keV b. The value is in good agreement with the previously reported [Formula: see text]-matrix result and also consistent within error bars with the published values.

Collision-induced absorption in nitrogen at low temperatures

1985 ◽  
Vol 63 (5) ◽  
pp. 625-631 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
L. A. A. Read
Keyword(s):  
Quadrupole Moment ◽  
Laser System ◽  
Far Infrared ◽  
Microwave Cavity ◽  
Jones Potential ◽  
Induced Absorption ◽  
Line Shapes ◽  
Theoretical Predictions ◽  
Theoretical Line

The collision-induced absorption (CIA) spectrum for nitrogen has been measured in the spectral region below 360 cm−1 at 126, 149, 179, and 212 K. The measurements have been obtained using Fourier transform infrared (FTIR) techniques, a far infrared (FIR) laser system operating at 84.2 and 15.1 cm−1, and microwave cavity techniques. The experimental line shapes have been compared with the theoretical predictions of Joslin, based on Mori theory, and of Joslin and Gray, based on information theory alone. The data have been used to determine the quadrupole moment employing various intermolecular potentials. One Lennard–Jones potential has resulted in a quadrupole moment of 1.51 B, the value that was used in generating the theoretical line shapes. These results, when combined with our forthcoming measurements on nitrogen mixed with methane and argon, may be helpful in determining the role of CIA in calculating the opacity of some planetary atmospheres.

scholarly journals Conotoxins as Sensors of Local pH and Electrostatic Potential in the Outer Vestibule of the Sodium Channel

2003 ◽  
Vol 122 (1) ◽  
pp. 63-79 ◽  
Author(s):  
Kwokyin Hui ◽  
Deane McIntyre ◽  
Robert J. French
Keyword(s):  
Lipid Bilayers ◽  
Sodium Channels ◽  
Electrostatic Potential ◽  
Single Channel ◽  
Local Environment ◽  
Bound State ◽  
Channel Changes ◽  
Voltage Dependent ◽  
Charged Ring ◽  
Derivatives Of

We examined the block of voltage-dependent rat skeletal muscle sodium channels by derivatives of μ-conotoxin GIIIA (μCTX) having either histidine, glutamate, or alanine residues substituted for arginine-13. Toxin binding and dissociation were observed as current fluctuations from single, batrachotoxin-treated sodium channels in planar lipid bilayers. R13X derivatives of μCTX only partially block the single-channel current, enabling us to directly monitor properties of both μCTX-bound and -unbound states under different conditions. The fractional residual current through the bound channel changes with pH according to a single-site titration curve for toxin derivatives R13E and R13H, reflecting the effect of changing the charge on residue 13, in the bound state. Experiments with R13A provided a control reflecting the effects of titration of all residues on toxin and channel other than toxin residue 13. The apparent pKs for the titration of residual conductance are shifted 2–3 pH units positive from the nominal pK values for histidine and glutamate, respectively, and from the values for these specific residues, determined in the toxin molecule in free solution by NMR measurements. Toxin affinity also changes dramatically as a function of pH, almost entirely due to changes in the association rate constant, kon. Interpreted electrostatically, our results suggest that, even in the presence of the bound cationic toxin, the channel vestibule strongly favors cation entry with an equivalent local electrostatic potential more negative than −100 mV at the level of the “outer charged ring” formed by channel residues E403, E758, D1241, and D1532. Association rates are apparently limited at a transition state where the pK of toxin residue 13 is closer to the solution value than in the bound state. The action of these unique peptides can thus be used to sense the local environment in the ligand-–receptor complex during individual molecular transitions and defined conformational states.

scholarly journals Low-Energy Electron Scattering by CS2 Molecules

2000 ◽  
Vol 53 (6) ◽  
pp. 785 ◽  
Author(s):  
Márcio H. F. Bettega
Keyword(s):  
Cross Section ◽  
Electron Scattering ◽  
Bound State ◽  
Elastic Cross Section ◽  
Low Energy ◽  
Energy Electron ◽  
Shape Resonance ◽  
Low Energy Electron

We report the integral elastic cross section for low-energy electron scattering by CS2 molecules. To perform our calculations we used the Schwinger multichannel method with pseudopotentials.We have found, in a static-exchange calculation, a shape resonance around 1 eV that belongs to the Π u symmetry.With the inclusion of polarisation effects only in that symmetry, we show that the resonance becomes a bound state. This result is in agreement with other results available in the literature.

scholarly journals Tailoring the lineshapes of coupled plasmonic systems based on a theory derived from first principles

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Jing Lin ◽  
Meng Qiu ◽  
Xiyue Zhang ◽  
Huijie Guo ◽  
Qingnan Cai ◽  
...  
Keyword(s):  
First Principles ◽  
Near Infrared ◽  
Coupled System ◽  
Bound State ◽  
Radiative Loss ◽  
Dark Mode ◽  
Optical Responses ◽  
Theoretical Predictions ◽  
Mutual Relations ◽  
Infrared Frequencies

Abstract Coupled photonic systems exhibit intriguing optical responses attracting intensive attention, but available theoretical tools either cannot reveal the underlying physics or are empirical in nature. Here, we derive a rigorous theoretical framework from first principles (i.e., Maxwell’s equations), with all parameters directly computable via wave function integrations, to study coupled photonic systems containing multiple resonators. Benchmark calculations against Mie theory reveal the physical meanings of the parameters defined in our theory and their mutual relations. After testing our theory numerically and experimentally on a realistic plasmonic system, we show how to utilize it to freely tailor the lineshape of a coupled system, involving two plasmonic resonators exhibiting arbitrary radiative losses, particularly how to create a completely “dark” mode with vanishing radiative loss (e.g., a bound state in continuum). All theoretical predictions are quantitatively verified by our experiments at near-infrared frequencies. Our results not only help understand the profound physics in such coupled photonic systems, but also offer a powerful tool for fast designing functional devices to meet diversified application requests.

Electrochemical feedback on strain dynamics in noble metal nanocatalysts

2021 ◽  
Author(s):  
Raphael Chattot ◽  
Isaac Martens ◽  
Marta Mirolo ◽  
Michal Ronovsky ◽  
Florian Russello ◽  
...  
Keyword(s):  
Structural Integrity ◽  
High Energy ◽  
Liquid Electrolyte ◽  
Model Description ◽  
Reactivity Descriptors ◽  
Storage Devices ◽  
Electrochemical Processes ◽  
Synchrotron Facility ◽  
Energy Conversion And Storage ◽  
Theoretical Predictions

Abstract The theoretical design of effective metal electrocatalysts for energy conversion and storage devices relies on the structure sensitivity of electrochemical processes to their catalyst materials, assuming the structural integrity during operation. However, theoretical predictions do not necessarily match practical performance. Here, by using high-energy X-ray diffraction from the new Extremely Brilliant Source of the European Radiation Synchrotron Facility (ESRF-EBS) on device-relevant Pd and Pt nanocatalysts during cyclic voltammetry experiments in liquid electrolyte, we quantitatively reveal how different electrochemical processes permanently affect the bulk microstructure of nanocatalysts in a distinctive fashion. The reported structural insights provide experimental access to reactivity descriptors such as adsorption and absorption trends operando. The ease and power of such an experimental approach at new and future beamlines is foreseen to guide computational model description of practical nanomaterials in electrochemical environment while providing a discovery platform toward the study of nanocatalysts encompassing a large variety of applications.

scholarly journals Reversible Silencing of CFTR Chloride Channels by Glutathionylation

2005 ◽  
Vol 125 (2) ◽  
pp. 127-141 ◽  
Author(s):  
Wei Wang ◽  
Claudia Oliva ◽  
Ge Li ◽  
Arne Holmgren ◽  
Christopher Horst Lillig ◽  
...  
Keyword(s):  
Chloride Channels ◽  
Single Channel ◽  
Bound State ◽  
Inhibitory Effect ◽  
Transmembrane Conductance Regulator ◽  
Mixed Disulfide ◽  
Channel Inhibition ◽  
Channel Opening ◽  
Mixed Disulfides ◽  
Signature Sequence

The cystic fibrosis transmembrane conductance regulator (CFTR) is a phosphorylation- and ATP-dependent chloride channel that modulates salt and water transport across lung and gut epithelia. The relationship between CFTR and oxidized forms of glutathione is of potential interest because reactive glutathione species are produced in inflamed epithelia where they may be modulators or substrates of CFTR. Here we show that CFTR channel activity in excised membrane patches is markedly inhibited by several oxidized forms of glutathione (i.e., GSSG, GSNO, and glutathione treated with diamide, a strong thiol oxidizer). Three lines of evidence indicate that the likely mechanism for this inhibitory effect is glutathionylation of a CFTR cysteine (i.e., formation of a mixed disulfide with glutathione): (a) channels could be protected from inhibition by pretreating the patch with NEM (a thiol alkylating agent) or by lowering the bath pH; (b) inhibited channels could be rescued by reducing agents (e.g., DTT) or by purified glutaredoxins (Grxs; thiol disulfide oxidoreductases) including a mutant Grx that specifically reduces mixed disulfides between glutathione and cysteines within proteins; and (c) reversible glutathionylation of CFTR polypeptides in microsomes could be detected biochemically under the same conditions. At the single channel level, the primary effect of reactive glutathione species was to markedly inhibit the opening rates of individual CFTR channels. CFTR channel inhibition was not obviously dependent on phosphorylation state but was markedly slowed when channels were first “locked open” by a poorly hydrolyzable ATP analogue (AMP-PNP). Consistent with the latter finding, we show that the major site of inhibition is cys-1344, a poorly conserved cysteine that lies proximal to the signature sequence in the second nucleotide binding domain (NBD2) of human CFTR. This region is predicted to participate in ATP-dependent channel opening and to be occluded in the nucleotide-bound state of the channel based on structural comparisons to related ATP binding cassette transporters. Our results demonstrate that human CFTR channels are reversibly inhibited by reactive glutathione species, and support an important role of the region proximal to the NBD2 signature sequence in ATP-dependent channel opening.

scholarly journals INTERACTION OF F- andD-STRINGS IN THE MATRIX MODEL

1998 ◽  
Vol 13 (12) ◽  
pp. 921-936 ◽  
Author(s):  
N. D. HARI DASS ◽  
B. SATHIAPALAN
Keyword(s):  
String Theory ◽  
Matrix Models ◽  
Matrix Model ◽  
Bound State ◽  
Model Description ◽  
Large N ◽  
The Matrix ◽  
M Theory

We study a configuration of a parallel F- (fundamental) and D-string in IIB string theory by considering its T-dual configuration in the matrix model description of M-theory. We show that certain nonperturbative features of string theory such as O(e-1/gs) effects due to soliton loops, the existence of bound state (1,1) strings and manifest S-duality, can be seen in matrix models. We discuss certain subtleties that arise in the large-N limit when membranes are wrapped around compact dimensions.

PHOTOEMISSION STUDY OF THE ELECTRONIC STRUCTURE OF SIZE-SELECTED Ptn — CLUSTERS DEPOSITED ON Ag(110)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 556-559 ◽  
Author(s):  
H.-V. ROY ◽  
J. BOSCHUNG ◽  
P. FAYET ◽  
F. PATTHEY ◽  
W.-D. SCHNEIDER
Keyword(s):  
Electronic Structure ◽  
Cluster Size ◽  
Crystal Surface ◽  
Bound State ◽  
In Situ Characterization ◽  
Theoretical Predictions ◽  
Photoemission Study ◽  
Energy Dependent

We report on a photoemission study (XPS, UPS) of the evolution of the electronic structure with cluster size of Pt n ( n = 1-10) clusters deposited on a Ag(110) single crystal surface. The clusters are produced by Xe-ion bombardment of a Pt target. The ionized clusters are mass-selected by a quadrupole mass spectrometer and guided to the substrate by an RF-mode only quadrupole. The substrate is in the center of the analysis chamber allowing in-situ characterization of the supported clusters. Photoemission spectra taken on submonolayer quantities of mass-selected monodispersed Pt clusters indicate individual discrete electronic structure features of the Pt 5d emission. In the atomic-like limit virtual bound state formation with different 5d3/2 and 5d5/2 line broadening is observed which points to an energy dependent Vsd hopping matrix element in agreement with theoretical predictions. With increasing cluster size the splitting between the bonding-like and antibonding-like Pt 5d states reflects the Pt-Pt interaction. The shift of the center of gravity of the Pt 5d state towards the Fermi energy and their concomittant broadening indicate the trend to Pt-metal formation.

scholarly journals Far Wing Asymmetry of Rotational Raman Lines in Hydrogen

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Magnus Gustafsson
Keyword(s):  
Raman Spectra ◽  
Line Profile ◽  
Threshold Energy ◽  
Rotational Transition ◽  
Hydrogen Gas ◽  
Shape Resonance ◽  
Pure Hydrogen ◽  
Line Shapes ◽  
Significant Intensity

Depolarized Raman spectra of compressed hydrogen gas have been computed rigorously previously for 36 K and 50 K (Gustafsson et al. (2009)). The far wings of the rotational lines show asymmetry that goes beyond that expected from the theory for intracollisional interference and Fano line shapes. Here we analyze the (0) line for pure hydrogen at 36 K in detail. The added asymmetry stems partly from a shape resonance which adds significant intensity to the higher frequency side of the line profile. The influence of the threshold energy for the rotational transition accounts for the remainder.

Sign in / Sign up

Export Citation Format

Share Document