Binding Energies Of Excited States Research Articles

Customized carbon dots as a fluorescent sensor for detecting paraquat through enhanced excited state binding energy

A novel fluorescent sensor utilizing customized carbon dots (CDs) has been developed for the rapid and efficient detection of the herbicide paraquat. The 4,4′-diamino-2,2′-stilbenedisulfonic acid (DSD acid) functionalized CDs (DSD-CDs) were synthesized by a hydrothermal method using citric acid and L-cysteine as precursors, followed by amidation with DSD acid. The resultant DSD-CDs exhibited bright blue fluorescence upon UV excitation. The fluorescence of the functionalized carbon dots was effectively quenched by paraquat, following a static quenching mechanism as confirmed by fluorescence lifetime measurements. Interestingly, the mechanism study revealed that the excited-state of the DSD-CDs could interact effectively with paraquat, resulting in stronger fluorescence quenching compared to the ground-state. The sensor showed high sensitivity, selectivity, and stability, with a wide linear range of 0.01 ∼ 2 mg/L (R2 = 0.997) and a low detection limit of 0.003 mg/L. The developed fluorescent sensor demonstrated exceptional potential for paraquat detection in actual samples, encompassing blood, urine, soybean, and river water, with recovery rates exceeding 83 % and relative standard deviations (RSD) below 10 %. This underscores its practical utility in environmental protection and clinical testing applications.

Analytic approximations to the strengths of near-threshold optical Feshbach resonances

Optical Feshbach resonances allow one to control cold atomic scattering, produce ultracold molecules, and study atomic interactions via photoassociation spectroscopy. In the limit of ultracold $s$-wave collisions, the strength of an optical Feshbach resonance can be expressed via an energy-independent parameter called the optical length. Here we give fully analytic approximate expressions for its magnitude applicable to near-threshold bound states of an excited molecular state dominated by a single resonant-dipole or van der Waals interaction. We express these magnitudes in terms of intuitive quantities, such as the laser intensity, the excited-state binding energy, the $s$-wave scattering length, and the Condon point. Additionally, we extend the utility of the optical length to associative stimulated Raman adiabatic passage in three-dimensional optical lattices by showing that the free-bound Rabi frequency induced by a laser coupling a pair of atoms in an optical lattice site can be approximately related to the trap frequency and the optical length.

Photo-ionisation cross-section of a hydrogenic donor in a near triangular quantum well

ABSTRACT Ground state and first excited state binding energies of a hydrogenic donor in a near triangular quantum Well (NTQW) composed of GaAs/Ga1-xAlxAs are calculated variationally as a function of well width and Al concentration. Photo-ionisation cross-section of the donor is also investigated as a function of photon energy, well width and Al concentration. Our results reveal that the peak value of photo-ionisation cross-section shows a turnover at the well width at which the binding energy is a maximum and at the Al concentration of 0.3. Photo-ionisation shows a strong dependence on well width, Al concentration and photon energy in NTQW than in other nanostructures.

Four-body system of He4 atoms: Dimer-dimer scattering

The strong short-range repulsion, characteristic to realistic interatomic potentials, complicates the description of weakly-bound few-body systems such as those of \He atoms. The present work proposes an approach for solving this problem and applies it to a realistic system of four ${}^4\mathrm{He}$ atoms. The potential is gradually softened such that rigorous four-body equations for bound and scattering tates can be accurately solved in the momentum-space framework, and the results are extrapolated back to the limit of the original potential. Linear correlations between three- and four body quantities are observed, and the accuracy of the procedure is improved by extrapolating in one of the three-body quantities. Results for the ${}^4\mathrm{He}$ tetramer ground and excited state binding energies and atom-trimer scattering agree well with at least some of earlier determinations and shed light on the existing disagreements. An additional case of the Phillips correlation line is established for the dimer-dimer scattering length. The trimer production rate via the ultracold two-dimer collisions is estimated, it exhibits significant finite-range effects despite the weak binding of the dimer.

Küresel Kuantum Noktasında Hidrostatik Basınç ve Dielektrik Sabitinin 2p Uyarılmış Durum Bağlanma Enerjisi ve Yabancı Atom Self-Polarizasyonuna Etkisi

GaAs/Ga1-xAlxAs küresel kuantum noktasında, hidrostatik basınca bağlı dielektrik sabitinin 2p uyarılmış durum bağlanma enerjisi ve yabancı atom self-polarizasyonuna etkisi nokta yarıçapı ve basıncın fonksiyonu olarak varyasyon yöntemi kullanılarak hesaplanmıştır. Elde edilen sonuçlara göre, dielektrik sabitinin ve hidrostatik basıncın 2p uyarılmış durum bağlanma enerjisini ve yabancı atom self- polarizasyonunu değiştirdiği görülmüştür. Yabancı atom self-polarizasyon ve bağlanma enerjisi nokta yarıçapına, hidrostatik basınca ve dielektrik sabitine bağlı değişimleri gösterilmiştir. Yabancı atom self-polarizasyonun küresel nokta yarıçapı ve hidrostatik basıncın artması ile azaldığı, bağlanma enerjisinin ise küresel nokta yarıçapının artması ile azaldığı hidrostatik basıncın artması ile arttığı görülmüştür. Elde edilen sonuçlar daha önce yapılmış çalışmalar ile uyumludur.

Cumulative effects of magnetic field and spin–orbit interaction (SOI) on excited binding energy of magnetopolaron in RbCl semi-exponential quantum well

In this paper, we investigate the cumulative effects of magnetic field and spin–orbit interaction (SOI) on the magnetopolaron-excited binding energy in RbCl semi-exponential quantum well material using Lee Low Pines Unitary Transformation and Linear Combination operator method. It’s shown that, the excited binding energy is strongly modified under the superposition of SOI and magnetic field. The predominant contribution is coming from the magnetic field strength compared to SOI constant $$\alpha_{r}$$ . Although neither the magnetic field nor the SOI can be neglected during the investigation of the properties of magnetopolaron, the barrier height of semi-exponential quantum well $$U_{0}$$ , the number of phonon $$N$$ and the spin–orbit interaction affect considerably the excited state binding energy. This analysis reveals the importance in nanotechnology of RbCl material due to the variability of their property.

Electric Field Effect on Excited State Binding Energy and Self-Polarization of a Hydrogenic Impurity in a Spherical Quantum Dot

Effects of the electric field and impurity position on the 2p-excited state self-polarization and binding energy of the electron-impurity in a spherical quantum dot are investigated as a function of the dot radius using variational approach. According to results, turning point of 2p-excited state binding energy changes with the electric field strength and position of impurity in the spherical quantum dot. Self-polarization and binding energy between the 1s-ground state and 2p-excited state of a hydrogenic donor impurity in SQD are presented as a function of the dot radius for different electric field value and impurity positions. Obtained numerical results show a good agreement with the literature.

Predicting the photoresponse of soot nuclei: Spectroscopic characteristics of aromatic aggregates containing five-membered rings

Establishing the mechanism for soot nucleation will require in situ experimental characterization of the identity and intermolecular interactions of the initial precursors, and electronic spectroscopy methods have the potential to do both. However, the optical response of polycyclic aromatic hydrocarbon (PAH) dimers and complexes differs significantly from that of the constituent monomers, and studies of soot precursor complexes have largely been limited to PAHs containing only six-membered aromatic rings. Hydrocarbons containing unsaturated five-membered rings are also present in high concentration in flames, and the photoresponse of complexes containing five-membered rings has not yet been examined. In this work, we elucidate the spectroscopic properties of small hydrocarbon complexes containing cyclopentadienyl groups or cyclopenta-fused groups, calculating ground- and excited-state binding energies, optimal excited-state geometries, repulsion energies, and fluorescence emission wavelengths. We show that excited-state distortion of cyclopentadienyl groups allows strong binding and low-energy fluorescence emission compared to similar-sized PAHs, and that a cyclopenta-fused group dramatically lowers the absorption and emission energies for acenaphthylene, dominating excited-state noncovalent interactions—findings that could shed light on the complex electronic properties of flames.

Influence of image charge effect on the binding energy of hydrogen-like donor impurity in a near-surface quantum well under transverse electric field

We present a systematic theoretical study of the influence of image charges on the spectrum of a shallow donor impurity located anywhere in a near-surface quantum well under the electric field applied along the growth direction of the system. We calculate the binding energies of the ground and excited donor impurity states in the effective-mass approximation using the variational method for various values of the quantum well width, electric field strength, and donor positions within the well. Theoretical results indicate that the role of image charges is especially important for small widths of a quantum well. In contrast to the ground state, the influence of image charges on the binding energy of excited states is significant only at small values of the electric field. Therefore such fields can serve as a means to control the transition energies between ground and first excited states.

Relativistic excited state binding energies and RMS radii of Λ-hypernuclei

Using an analytical solution for the relativistic equation of single [Formula: see text]-hypernuclei in the presence of Woods–Saxon (WS) potential we present, for the first time, an analytical form for the excited state binding energies of 1p, 1d, 1f and 1g shells of a number of hypernuclei. Based on phenomenological analysis of the [Formula: see text] binding energies in a set of [Formula: see text]-hypernuclei, the WS potential parameters are obtained phenomenologically for the set of [Formula: see text]-hypernuclei. Systematic study of the energy levels of single [Formula: see text]-hypernuclei enables us to extract more detailed information about the [Formula: see text]-nucleon interaction. We also study the root mean square (RMS) radii of the [Formula: see text] orbits in the hypernuclear ground states. Our results are presented for several hypernuclei and it is shown that our results for the binding energies are in good agreement with experimental data.

Electric field effect on lowest excited-state binding energy of hydrogenic impurity in (In,Ga)N parabolic wire

Externally applied electric field and effective radius effects are investigated on the lowest excitedstate shallow-donor binding energy in (In,Ga)N-GaN parabolic wire within the framework of single band effective-mass approximation. The calculations are performed using the finite-difference method within the quasi-one-dimensional effective potential model. Our results reveal that: (i) the probability density is the largest on a circularity whose radius is the effective radius, (ii) the lowest excited-state binding energy is the largest for impurity located on this circularity while it starts to decrease when the impurity is away from the circularity and (iii) the binding energy is strongly-dependent on the complex interplay of spatial confinement, coulomb interaction and applied electric field.

Binding Energy of Donor Impurity in a Rectangular Semiconductor GaAs Quantum Dot with Electric Field

Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first few excited state binding energies of a donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. We discuss detailedly dependence of the binding energies on the impurity positions. The results show that the binding energy is the largest when the impurity is located at the center of RQD with zero field and is lowest when the impurity is located at the corner of the RQD. The peak strengths and positions of the probability density in RQD appear to be the critical control on such impurity-induced dependence. We believe our results can provide an indication for design of some photoelectric devices constructed based on GaAs RQD structures.

The effect of hydrostatic pressure on the binding energy and diamagnetic susceptibility of a laser dressed donor impurity in a GaAs/GaAlAs nanowire superlattice

In this paper the effects of hydrostatic pressure and laser radiation on the binding energy and diamagnetic susceptibility of an off-center hydrogenic donor impurity in a nanowire superlattice (NWSL) are studied. The energy eigenvalues and corresponding wave functions of ground and first excited states are numerically computed using finite difference method for a NWSL with circular cross-section which involved an array of spherical quantum dots (QDs). The numerical results show that oscillatory behaviors appear in binding energies and diamagnetic susceptibilities of ground and first excited states as impurity shifts away from center of QDs. Maximum values of ground state binding energy (first excited state binding energy) occur when impurity is located at the center of QDs (at the center of barriers). Additionally, binding energies of ground and first excited states shift towards higher (lower) energies as pressure (laser radiation) increases. An opposite behavior is observed for absolute value of diamagnetic susceptibility as pressure or laser radiation increases. Also, as the QDs’ volume increases the binding energies (I) decrease or (II) increase, reach maximum values and then decrease; which strongly depend on the position of impurity.

Binding energy of the ground and first few excited states of hydrogenic donor impurity in a rectangular GaAs quantum dot in the presence of electric field

Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first 9 excited-state binding energies of a hydrogenic donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. The analytical form of the quasi-one-dimensional effective potential replacing the three-dimensional Coulomb potential in our model is derived by Fourier transforms. We discuss detailedly dependence of the binding energies on the impurity positions and electric fields. For the ground-state binding energy, our results qualitatively agree with that of Mendoza et al. (2005) in which they only calculated the ground-state binding energies in cubic quantum dots by variational method. However, for first 9 excited-state binding energies, such dependence has complex manner since there are two or three peaks in the electronic probability density distribution curves. The strengths and positions of these peaks in RQD affect the interaction potential between electron and impurity, which appears to be the critical control on the binding energies of impurity. The applied electric field pushes the positions of these peaks downwards, and the strengths of peaks located at the upper half of RQD increase while the strengths of lower peaks firstly decrease, then increase with increasing electric field. The high peak strength can lead to increase of the binding energy while the large distance between the position of peak and impurity center results in reduce of the energy, which is an interesting competition. This competition is more obvious for excited-state binding energies of off-central impurity.

A Theoretical Study of the Formation of Benzene Excimer: Effects of Geometry Relaxation and Spin-state Dependence

Geometry relaxation effects on the formation of benzene excimer were investigated by means of ab initio calculation at SOS-CIS(D0)/aug-cc-pVDZ level. In the case of T-shaped dimer configuration, intermolecular interactions in the excited states are found to be nearly the same as those in the ground state and structural deformations are limited within a single molecule; the geometry relaxation effects are then negligible and singlet-triplet energy gap remains constant. As for face-to-face eclipsed dimer, on the other hand, both molecules undergo structural change. As a result, intermolecular interactions in the excited states are significantly different than those in the ground state. Although the intermolecular distances obtained from potential energy curve calculation with frozen molecular structures are in qualitative agreement, the excitedstate binding energies are notably overestimated with respect to those at optimized structures. In particular, the effects are calculated to be larger in T1 state and hence singlet-triplet energy gap, which reduces markedly in this configuration, is underestimated without relaxation.

Lowest Excited-State Impurity Binding Energy in InGaN/GaN Parabolic QWW: Magnetic Field Effect

In this paper, we have investigated the magnetic field effect on the lowest excited-state binding energy of hydrogenic shallow-donor impurity in wurtzite (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) using the finite-difference method within the quasi-one-dimensional effective potential model. The calculations are performed within the framework of the effective mass approximation. A cylindrical QWW effective radius is taken into account to describe the lateral confinement strength. The numerical results show that: (i) the probability density is the largest on a circularity whose radius is the effective radius and (ii) the lowest excited-state binding energy is the largest when an impurity is located on this circularity while it starts to decrease as the impurity is away from the circularity.

Binding energy and diamagnetic susceptibility of an on-center hydrogenic donor impurity in a spherical quantum dot placed at the center of a cylindrical nano-wire

The binding energy and diamagnetic susceptibility of an on-center hydrogenic donor impurity in an InAs spherical quantum dot placed at the center of a GaAs cylindrical nano-wire have been investigated using finite element method in the framework of the effective mass approximation. The binding energy and diamagnetic susceptibility are calculated as a function of the dot radius, nano-wire radius and nano-wire height. The results show that as the dot radius increases (I) for a dot radius smaller than some critical value, the effect of the spherical confinement on the energy levels becomes negligible and the energies remain constant, for a dot radius larger than some specific value, the energy levels decrease (II) the ground and the first excited state binding energies increase, reach a maximum and then decrease (III) the ground state diamagnetic susceptibility increases, reach a maximum and then decreases (IV) the first excited state diamagnetic susceptibility increases, indicating two maxima and then decreases. The effects of the nano-wire dimensions on the binding energy and diamagnetic susceptibility have also been studied. We found that the binding energy and diamagnetic susceptibility decrease reach a minimum value and then increase as the nano-wire radius increases. Finally we found that as the height of the nano-wire increases the ground state binding energy decreases, reaches a minimum value and then increases but the first excited state binding energy decreases and reaches a constant value.

EFFECT OF LASER ON THE NONPARABOLICITY OF THE CONDUCTION BAND AND HYDROGENIC IMPURITY STATES IN A SEMICONDUCTOR QUANTUM WELL

The effect of laser on the nonparabolicity of the conduction band for hydrogenic donor states like 1s, 2s, 2p± and 2p0 in a GaAs/Al x Ga 1-x As quantum well have been computed in a finite barrier model using variational principle in the effective mass approximation. The limiting values of the ground state and few excited state binding energies for a laser dressed-donor have been obtained. The results are presented and discussed.

Hydrogenic impurity bound polaron in a parabolic quantum dot with arbitrary electron–phonon coupling strength

A variational approach is employed to obtain the ground and the first excited state binding energies of an electron bound to a hydrogenic impurity in a polar semiconductor quantum dot (QD) with symmetric parabolic confinement in both two and three-dimensions. We perform calculations for the entire range of the electron–phonon coupling constant and the Coulomb binding parameter and for arbitrary confinement length. It is found that the binding energy of ground and first excited state is larger in a two-dimension (2D) dot than in a three-dimension (3D) dot and this trend is more pronounced with the increase of the electron–phonon coupling constant for the same value of the Coulomb binding parameter and confinement length. Furthermore, the ground and the first excited state binding energy increases with increasing the Coulomb binding parameter in both 2D and 3D QDs for the same electron–phonon coupling constant.

Stark Effect Dependence on Hydrogenic Impurities in GaAs Parabolic Quantum-Well Wires

The ground-state and lowest excited-state binding energies of a hydrogenic impurity in GaAs parabolic quantum-well wires (QWWs) subjected to external electric and magnetic fields are investigated using the finite-difference method within the quasi-one-dimensional effective potential model. We define an effective radius ρeff of a cylindrical QWW, which can describe the strength of the lateral confinement. For the ground state, the position of the largest probability density of electron in x-y plane is located at a point, while for the lowest excited state, is located on a circularity whose radius is ρeff. The point and circularity are pushed along the left half of the center axis of the quantum-well wire by the electric field directed along the right half. When an impurity is located at the point or within the circularity, the ground-state or lowest excited-state binding energies are the largest; when the impurity is apart from the point or circularity, the ground-state or lowest excited-state binding energies start to decrease.