Optical Potential Research Articles

Thiophene-centered PMMA unified thin films with electrical, photoluminescence, and third-order nonlinear optical potentials for optoelectronic applications

In the present work, we have investigated the electrical, linear, and nonlinear optical parameters of thiophene-centering chalcone doped PMMA thin films. Using a standard spray pyrolysis technique, (E)− 1-(thiophen-2-yl)− 3–3(3,4,5-trimethonyl) prop-2-en-1-one blended PMMA thin films were deposited for different chalcone concentrations (10%, 30%, and 50% wt.). With the advent of FESEM analysis, the uniform and consistent behavior of the deposited thin film was verified. The optical band gap is found to diverge from 3.83 to 3.77 eV with concentration using UV–visible spectroscopy, and photoluminescence studies show that material emits in the blue band region. The deposited thin films show nonlinear absorption coefficients (β) and third-order nonlinear optical susceptibility Imχ(3) in the order of 10−4 cm/W and 10−7 e.s.u., respectively. I-V curves revealed that the electrical conductivity of chalcone doped PMMA thin films ranges from 1.78 to2.39μS/cm. Non-linear optical findings of deposited thin films are recommended for optoelectronic device applications.

Unraveling Optical and Electrical Gains of Perovskite Solar Cells with an Antireflective and Energetic Cascade Electron Transport Layer

Electron transport layers (ETLs) are imperative in n-i-p structured perovskite solar cells (PSCs) because of their capability to affect light propagation, electron extraction, and perovskite crystallization, and any mismatch of optical constants, band position, and surface potential between the ETLs and the perovskites can cause unintentional optical and electrical losses. Herein, an antireflective and energetic cascade bilayer ETL with ubiquitously used SnO2 and TiO2 was constructed at 150 °C for PSCs, and the in-depth mechanism for performance improvement was systematically unraveled. It was revealed that the construction of an ETL with gradually increasing refractive indices can circumvent light reflection loss, resulting in enhanced photocurrent. The combined ETL forms an energetic cascade to promote electronic conductivity and facilitate electron extraction with reduced energy loss. Moreover, topologic perovskite growth with improved crystallinity and vertical orientation was preferred owing to the relative dewetting behavior, leading to reduced defect states and enhanced carrier mobility in the perovskite layer.

Particle Trapping Properties of Metal Annular Slits under Vector Field Excitation

This article presents the particle capture performance of annular slits, which offer a simple alternative to complex micro/nano structures used to excite and focus surface plasmon polaritons (SPPs). Additionally, the annular slits are compatible with a variety of vector light fields, generating diverse SPP field distributions under their excitation. These SPP fields can be regulated by varying the vector light field parameters, thereby offering the annular slit structure the ability to flexibly capture and manipulate particles. The rotation and movement of captured objects can be achieved by changing the position and phase difference of the incident beams with linear polarization. Different material and sized metallic particles can be stably captured with a radially polarized beam excitation due to the strong convergence. These capabilities are demonstrated by evaluating the optical force and trapping potential based on the finite difference time domain (FDTD) simulation. This study provides valuable insights into the practical application of annular slits for particle capture and manipulation.

Energy dependent optical potential for reactions involving Li6,7 projectiles

The dependence of the optical Cook potential on the bombarding energies of reactions involving $^{6,7}\mathrm{Li}$ projectiles has been analyzed. It has been found that, for reactions occurring close to or below the Coulomb barrier, the depth of the imaginary potential should be reduced from the value originally proposed by Cook in order to achieve better agreement with experimental elastic data. A modified version of the Cook potential is presented for both lithium isotopes, and its results are compared with those obtained using other existing optical potentials. Finally, the effects of the corrections made to the original Cook potential are studied in a one-neutron transfer case, highlighting the importance of using the correct optical potential for different reaction channels.

Generating soliton trains through Floquet engineering

We study a gas of interacting ultracold bosons held in a parabolic trap in the presence of an optical lattice potential. Treating the system as a discretized Gross-Pitaevskii model, we show how Floquet engineering, by rapidly ``shaking'' the lattice, allows the ground state of the system to be converted into a train of bright solitons by inverting the sign of the hopping energy. We study how the number of solitons produced depends on the system's nonlinearity and the curvature of the trap, show how the technique can be applied in both the high- and low-driving-frequency regimes, and demonstrate the phenomenon's stability against noise. We conclude that the Floquet approach is a useful and stable method of preparing solitons in cold-atom systems.

The selective role of the orbital angular momentum on the reaction stereo-dynamics

This paper reports on the characterization of the stereo-dynamic controlling three different chemi-ionization reactions, recent objective of our study, since they participate to the balance of phenomena occurring in plasma, interstellar medium, planetary atmospheres, flames and lasers. The optical potential, obtained by a phenomenological method and defined in the whole space of the relative configurations of reagents, has been formulated in an accurate and internally consistent way for three different systems. Some cuts of the multidimensional potential, that asymptotically correlate with a specific fine level of the open shell atom and/or with a defined orientation of the molecular reagent, have been exploited in the present study to emphasize crucial features of the collision dynamics along selected entrance channels of the reactions. Consistently, basic quantities determining the topology of the reaction stereo-dynamics have been properly defined, emphasizing in the three cases relevant changes in the microscopic reaction evolution. Much attention focused on the selectivity of the orbital angular momentum, affecting each collision event at any chosen collision energy. It controls the relative weight of two different reaction mechanisms. The direct reaction mechanism is driven by short-range chemical forces, promoting, by direct electron transfer between reagents, a prototypical elementary oxidation reaction. The indirect mechanism, controlled by the combination of long-range chemical and physical forces, can be triggered by a virtual photon exchanged between reagents, promoting a sort of photo-ionization process. Obtained results and emphasized differences appear to be of general interest for many other elementary processes, more difficult to characterize at this level of detail.Graphic abstract

Analysis of an image noise sensitivity mechanism for matrix-operation-mode-decomposition and a strong anti-noise method.

Mode decomposition (MD) based on the matrix operation (MDMO) is one of the fastest mode decomposition methods in fiber laser which has great potential for optical communications, nonlinear optics and spatial characterization applications. However, we found that the image noise sensitivity is the main limit to the accuracy of the original MDMO method, but improving the decomposition accuracy by using conventional image filtering methods is almost ineffective. By using the norm theory of matrices, the analysis result shows that both the image noise and the coefficient matrix condition number determine the total upper-bound error of the original MDMO method. Besides, the greater the condition number, the more sensitive of MDMO method is to noise. In addition, it is found that the local error of each mode information solution in the original MDMO method is different, which depends on the L2-norm of each row vector of the inverse coefficient matrix. Moreover, a more noise-insensitive MD method is achieved by screening out the information corresponding to large L2-norm. In particular, selecting the higher accuracy among the original MDMO method and such noise-insensitive method as the result in a single MD process, a strong anti-noise MD method was proposed in this paper, which displays high MD accuracy in strong noise for both near-filed and far-filed MD cases.

Реакція 10В(15N,14С)11С при енергії 81 МеВ, спектроскопічні фактори реакції та взаємодія ядер 14С + 11С

New experimental data of angular distribution cross-sections for the 10В(15N,14С)11С reaction at the energy Еlab(15N) = 81 MeV were obtained for the ground states of 14С, 11С nuclei and 2.00 MeV (1/2-), 4.31 MeV (5/2-), 4.31 MeV (3/2-) excited states of 11С nucleus. The experimental data were analyzed within the coupled-reaction-channels (CRC) method. In the CRC calculations, the 15N + 10В Woods - Saxon (WS) optical potential obtained from the CRC analysis of the experimental elastic and inelastic data of these nuclei was used and parameters of the 14С + 11С WS optical potential were deduced from the analysis of the 10В(15N,14С)11С reaction experimental data. Spectroscopic amplitudes of nucleons and cluster transfers were calculated within the translation-invariant shell model.

Improved design and experimental demonstration of ultrahigh-Q C6-symmetric H1 hexapole photonic crystal nanocavities.

An H1 photonic crystal nanocavity (PCN) is based on a single point defect and has eigenmodes with a variety of symmetric features. Thus, it is a promising building block for photonic tight-binding lattice systems that can be used in studies on condensed matter, non-Hermitian and topological physics. However, improving its radiative quality (Q) factor has been considered challenging. Here, we report the design of a hexapole mode of an H1 PCN with a Q factor exceeding 108. We achieved such extremely high-Q conditions by varying only four structural modulation parameters thanks to the C6 symmetry of the mode, despite the need of more complicated optimizations for many other PCNs. Our fabricated silicon H1 PCNs exhibited a systematic change in their resonant wavelengths depending on the spatial shift of the air holes in units of 1 nm. Out of 26 such samples, we found eight PCNs with loaded Q factors over one million. The best sample was of a measured Q factor of 1.2 × 106, and its intrinsic Q factor was estimated to be 1.5 × 106. We examined the difference between the theoretical and experimental performances by conducting a simulation of systems with input and output waveguides and with randomly distributed radii of air holes. Automated optimization using the same design parameters further increased the theoretical Q factor by up to 4.5 × 108, which is two orders of magnitude higher than in the previous studies. We clarify that this striking improvement of the Q factor was enabled by the gradual variation in effective optical confinement potential, which was missing in our former design. Our work elevates the performance of the H1 PCN to the ultrahigh-Q level and paves the way for its large-scale arrays with unconventional functionalities.

Consistent optical potential for incident and emitted low-energy α particles. III. Nonstatistical processes induced by neutrons on Zr, Nb, and Mo nuclei

The reliability of a previous $\alpha$-particle optical-model potential (OMP) on nuclei with mass number 45$\leq$$A$$\leq$209 was proved for emitted $\alpha$ particles as well, for proton--induced reactions on Zn isotopes [Phys. Rev. C {\bf 91}, 064611 (2015), Paper I]. However, the same was not the case of neutrons on Zr stable isotopes [Phys. Rev. C {\bf 96}, 044610 (2017), Paper II]. A recent assessment of this potential also for nucleon--induced $\alpha$-emission on $A$$\sim$60 nuclei, including pickup direct reaction and eventual Giant Quadrupole Resonance (GQR) $\alpha$-emission, is completed for neutrons incident on Zr, Nb, and Mo stable isotopes. Consistent sets of input parameters, determined through analysis of independent data, is involved while no further empirical rescaling factors of the $\gamma$ and nucleon widths have been involved. A suitable account of all competitive reaction channels is confirmed by careful uncertainty analysis, to avoid parameter ambiguities and/or error compensation. Additional validation of this potential is also supported by recently measured $(\alpha,\gamma)$ and $(\alpha,n)$ cross--sections of Zr and Mo nuclei. An increase of the $\alpha$-emission beyond the statistical predictions, through consideration of additional reaction channels of the pickup direct interaction and {\it like}--GQR decay, makes possible the description of both absorption and emission of $\alpha$ particles by the same optical potential.

Nonlocal optical potential with core excitation in [formula omitted] and [formula omitted] reactions

We propose a new nonlocal form of the nucleon-nucleus optical potential and demonstrate its reliability. We extend the nonlocal potential to include the excitation of the nuclear core and develop energy-independent proton-Be10 potential reasonably reproducing the experimental data at low energies. We apply the new potential to the study of deuteron stripping and pickup reactions Be10(d,p)11Be and Be11(p,d)10Be using rigorous three-body Faddeev-type equations for transition operators that are solved in the momentum-space partial-wave framework. The achieved description of the experimental data is considerably more successful as compared to previous studies with local potentials. The values of spectroscopic factors consistent with the data are determined, exhibiting only weak energy dependence. The results possibly indicate an increased predicting power of the proposed calculational scheme.

Determination of 170,172Yb(α,n)173,175Hf reaction cross sections in a stacked-target experiment

Background: For understanding the synthesis of elements in the universe, precise knowledge of reaction rates and cross sections is paramount. This is especially true for the $p$ process because its study requires large network calculations including thousands of nuclei and nuclear reactions with little room for simplification. Therefore, robust theoretical methods for predicting cross sections are needed which are usually based on Hauser-Feshbach calculations. These calculations use physics input in the form of $\ensuremath{\gamma}$-ray strength functions, nuclear level densities, and particle $+$ nucleus optical-model potentials. These have to be constrained using experimental results.Purpose: To constrain the $\ensuremath{\alpha}$ optical-model potential $\ensuremath{\alpha}$-induced reactions are well suited. The ytterbium isotopic chain not only offers multiple stable isotopes on which cross sections can be measured and insights into the evolution of the $\ensuremath{\alpha}$ optical-model potential with the neutron-to-proton ratio can be gained but also includes the $p$ nucleus $^{168}\mathrm{Yb}$. Its abundance is significantly impacted by the $^{164,166}\mathrm{Yb}(\ensuremath{\alpha},\ensuremath{\gamma})$ reactions and is, therefore, also affected by the constraints resulting from the experiment presented in this paper.Method: To study the $^{170,172}\mathrm{Yb}(\ensuremath{\alpha},n)^{173,175}\mathrm{Hf}$ reaction cross sections the activation method was used. During irradiation the targets were arranged in stacks of four to reduce the required irradiation time. Aluminum degrader foils served as backings. The average interaction energy inside each ytterbium layer was determined via geant4 simulations. A third layer, consisting of manganese, was used to verify the simulations by comparing the measured $^{55}\mathrm{Mn}(\ensuremath{\alpha},(2)n)^{57,58}\mathrm{Co}$ reaction cross sections to previous results. For irradiation the 10 MV FN tandem accelerator located at the University of Cologne was used and the activation measurement was performed utilizing the Cologne Clover Counting setup consisting of two clover-type high-purity germanium detectors in a face-to-face geometry.Results: For the $^{170}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction seven cross sections at center-of-mass energies between 12.7 and 16.5 MeV were measured. For the $^{172}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction six cross sections for center-of-mass energies of 13.1 to 16.5 MeV could be determined with an additional upper limit at ${E}_{\mathrm{c}.\mathrm{m}.}=12.3$ MeV.Conclusion: Comparisons to theoretical models show that state-of-the-art $\ensuremath{\alpha}$-optical model potentials reproduce the measured cross sections very well. The ratios of $(\ensuremath{\alpha},n)$ reaction cross sections in the ytterbium isotopic chain can be accurately reproduced as well.

CNOK: A C++ Glauber model code for single-nucleon knockout reactions

A C++ program package was developed to calculate parallel momentum distributions (including the stripping mechanism and the diffractive dissociation mechanism) of the heavy residue (core) in single-nucleon knockout reactions induced by intermediate-energy (around and more than tens of MeV per nucleon) beams of stable and radioactive atomic nuclei. The program implements the Glauber reaction model that is based on the eikonal approximation and the sudden approximation when dealing with the scattering process, and uses a t-ρ-ρ method to build the projectile-target scattering optical potential, where the nucleonic densities of the core and the target are needed as input. The radial wavefunction of the valence nucleon is solved by a built-in bound-wave solver driven by a globally convergent search engine for optimized potential parameters of the valence nucleon to reproduce user-specified separation energies and root-mean-square (rms) radii of the valence nucleon. The YAML file format is adopted to facilitate user input. The program is expected to especially serve the interpretation of data analysis results of single-nucleon knockout from radioactive ion beams (RIBs), where the experimental practitioners may be more conversant with C++. Program summaryProgram Title: CNOKCPC Library link to program files:https://doi.org/10.17632/dmffpbjhsh.1Developer's repository link:https://gitee.com/asiarabbit/cnokLicensing provisions: GPLv3Programming language: C++Nature of problem: This program calculates the single-particle reaction cross sections of single-nucleon removal from stable and radioactive nuclei impinging on a light composite (i.e. non-hydrogen, e.g. carbon and beryllium) target at intermediate energies (around and more than tens of MeV per nucleon), and the parallel momentum (stripping+diffractive dissociation) distributions of the core, for a pure valence configuration (bound core state+valence nucleon single-particle orbit).Solution method: The bound radial wavefunction of the valence nucleon in a Woods-Saxon (WS) potential is solved following the method of shooting to a fitting point, where the wavefunction is integrated with Runge-Kutta method from 0 and some large distance r∞ to a matching point rm near the nuclear surface. The process is iterated to optimize the eigenvalue Enlj by joining the two waves at rm “smoothly”. Most integrals are evaluated with Simpson's rules, while some with Romberg integration. Searching in the (V0,r0) space of the central WS potential to reproduce the user-specified separation energy and rms radius of the valence nucleon is done via a globally convergent Newton-Raphson root-finding routine for nonlinear systems of equations.Additional comments including restrictions and unusual features: User input is read in with YAML parser (yaml-cpp). Global parameters are readily accessed and uniformly modified in a singleton class. General algorithms (integration, interpolation, minimization, and root-finding routines) are implemented with C++ template class or functors, which adapt to different data types and/or function types. Various batch modes are wrapped in the program package to save user time. For instance, in one run, with the batch mode, one can calculate inclusive single-nucleon removal cross section involving many valence configurations, the relevant inclusive core momentum distribution, and similarly for a series of projectile+target combinations in study of systematics, as is frequently encountered in the study of quenching of single-particle-orbit occupancies (spectroscopic factors) in single-nucleon knockout reactions. Unit tests with Catch are widely deployed to facilitate debugging. C++11 support is required for compilers.

The Transport phenomena in CdTe:Cl and CdTe:Cu - calculation from the first principles

In the presented article the method of determining the energy spectrum, the wave function of the charge carrier and the crystal potential in CdTe at an arbitrarily given temperature is considered. Using this approach within the framework of the supercell method the temperature dependences of the ionization energies of various types of defects caused by the introduction of chlorine and copper impurities in cadmium telluride are calculated. Also the offered method allows to define the temperature dependence of the optical and acoustic deformation potentials and as well as the dependence on the temperature the charge carrier’s scattering parameters on ionized impurities, polar optical, piezooptic and piezoacoustic phonons. Within the framework of short-range scattering models the temperature dependences of the charge carrier’s mobility and Hall factor are considered.

Velocity dependent potential for alpha 40Ca-elastic scattering

Angular distribution of the differential cross section of α40Ca elastic scattering has been investigated in the anomalous large angle scattering (ALAS) region by a nonlocal velocity dependent optical potential with surface term. The geometrical potential parameters were fixed and the depths of the potential were determined by fitting elastic angular distribution over the energy range (23–53.9 MeV). The real and the imaginary parts of the optical potential used here are of Woods–Saxon form factors. An energy dependence of the potential depths has been investigated at fixed geometrical potential parameters.

Anisotropy effects on the quantum transport of atomic matter waves

We discuss effects of anisotropic scattering in transport properties of ultracold atoms in three-dimensional optical potentials. Within the realm of the first Born approximation, we calculate the self energy, the scattering mean free time, the scattering mean free path, and the anisotropy factor. The behavior of the diffusion constant as a function of the wavenumber is also examined in diffusive and weak localization regimes. We show that these quantities are affected by quantum corrections due to the interference caused by disorder. The dimensionless conductance is evaluated using the scaling theory of localization. Our results are compared with previous theoretical and the experimental results.

Study of6,8He+p elastic scattering using the BHF formalism with three-body forces

In the present work, we have analyzed the elastic scattering data of6He+p at 25.6, 38.6, 40.9, and 71 MeV/A and8He+p at 15.6, 25.6, 32.5, 66, and 72 MeV/A, using the microscopic local optical potential calculated within the framework of the Brueckner–Hartree–Fock (BHF) formalism. The calculation requires mainly two inputs: (1) the nucleon–nucleon (NN) interaction and (2) the nucleon distributions in target nuclei. In the present work, realistic internucleon (NN) potential from Argonne v18 (AV18) and the Urbana IX (UVIX) model of three-body forces with several nucleon density distributions are used for generating the nucleon–nucleus optical potential. We have used the exact method for calculating both the direct and the exchange parts of the spin–orbit potential. We confirm the earlier results that the spin–orbit potential for these neutron-rich nuclei is diffused and extended. Our results show that the different density distributions reproduce rather well the experimental differential cross sections for both isotopes, while the phenomenological density with a two-neutron halo gives satisfactory results for6He-p analyzing power data. None of the densities used for8He can reproduce the experimentally analyzed power data. Our analysis reveals that the calculated microscopic optical potentials, with and without three-body forces using the BHF approach, provide satisfactory agreement with the elastic scattering data for6,8He+p.

Proton s -resonance states of C12 and O14,15 within the Skyrme Hartree-Fock mean-field framework

The excitation functions of proton elastic scattering on $^{12}\mathrm{C}$ and $^{14,15}\mathrm{O}$ nuclei at the energies near the proton-emission threshold are calculated using the Skyrme Hartree-Fock (SHF) in continuum approach. For each excitation function, the first resonance is identified as the $s$-state resonance of the mean-field theory. For $^{15}\mathrm{O}$, whose ground-state spin is nonzero, the $s$-state resonance splits into two resonances via the spin-spin component of the optical potential. With a slight adjustment of the strength of the central potential, which is obtained from the SHF in continuum approach, the excitation functions of proton elastic scattering for the three nuclei can be explained with high accuracy. The proposed framework can provide a practical method to explain nuclear scattering at the energies near the proton-emission threshold with minimal experimental input.

Reaction channel contributions to the triton + Pb208 optical potential

Background: Well-established coupled channel and coupled reaction channel (CRC) processes make contributions to elastic scattering that are not included in standard folding models of the optical model potential (OMP). Such contributions have been established for $^{3}\mathrm{He}$ interacting with $^{208}\mathrm{Pb}$ but the corresponding contributions for $^{3}\mathrm{H}$ are expected to be different, particularly for pickup coupling.Purpose: To establish and characterize the contribution to the interaction potential between $^{3}\mathrm{H}$ and $^{208}\mathrm{Pb}$ that is generated by coupling to proton pickup (outgoing $^{4}\mathrm{He}$) channels; also to study the contribution of collective states and identify effects of dynamical nonlocality due to these couplings.Methods: CRC calculations, including coupling to collective states, will provide the elastic channel $S$-matrix ${S}_{lj}$ resulting from the included processes. Inversion of ${S}_{lj}$ will produce the local potential that yields, in a single channel calculation, the elastic scattering observables from the coupled channel calculation. Subtracting the bare potential from the inverted CRC potential yields a local and $l$-independent representation of the dynamical polarization potential (DPP). From the DPPs due to a range of combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.Results: Coupling to $^{4}\mathrm{He}$ channels makes a smaller contribution to the $^{3}\mathrm{H}$ interaction than it does for incident $^{3}\mathrm{He}$. On the other hand coupling to inelastic channels makes a greater contribution than it does for $^{3}\mathrm{He}$. The nonadditivity of the DPPs implies their dynamical nonlocality.Conclusions: The DPPs established here challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of $^{3}\mathrm{H}$ from nuclei. Coupling to proton pickup channels induces dynamical nonlocality in the $^{3}\mathrm{H}$ OMP with implications for direct reactions involving $^{3}\mathrm{H}$. Departures from a smooth radial form for the $^{3}\mathrm{H}$ OMP should be apparent in high quality fits to suitable elastic scattering data. Future theories of the interaction of $^{3}\mathrm{H}$ with nuclei should include some representation of outgoing $^{4}\mathrm{He}$.

Microscopic Optical Potentials: recent achievements and future perspectives

Few years ago we started the investigation of microscopic Optical Potentials (OP) in the framework of chiral effective field theories [1, 2] and published our results in a series of manuscripts. Starting from the very first work [3], where a microscopic OP was introduced following the multiple scattering procedure of Watson [4], and then followed by Refs. [5, 6], where the agreement with experimental data and phenomenological approaches was successfully tested, we finally arrived at a description of elastic scattering processes off non-zero spin nuclei [7]. Among our achievements, it is worth mentioning the partial inclusion of three-nucleon forces [8], and the extension of our OP to antiproton-nucleus elastic scattering [9]. Despite the overall good agreement with empirical data obtained so far, we do believe that several improvements and upgrades of the present approach are still to be achieved.In this short essay we would like to address some of the most relevant achievements and discuss an interesting development that, in our opinion, is needed to further improve microscopic OPs in order to reach in a near future the same level of accuracy of the phenomenological ones.