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In this study, photoionization cross sections of guest hydrogen atom in endohedral fullerene (H@Cn${\text{H@C}}_{n}$) modeled by the Woods–Saxon confinement potential implanted in the nonideal classical plasma (NICP) under spherical confinement are reported for the first time in the related literature. The relevant wave equation is solved numerically via the tridiagonal matrix method and then the energy levels, bound and continuum wave functions are interpreted. Plasma effect is examined by considering plasma temperature and density and is evaluated in the photoionization process. Since the plasma modifies the discrete and continuum spectra by changing the potential energy of hydrogen atom, it closely affects the overlapping of the wave functions of ground state and continuum state. This effect has a distinct response on photoionization resonances. Using different values of endohedral confinement parameters, which means regarding different types of fullerenes, detailed analysis of energy levels, bound and continuum wave functions, and photoionization cross sections are provided by evaluating confinement width, depth, smoothing effect and distance from the spherical encompassement center. The photoionization process of H@Cn${\text{H@C}}_{n}$ implanted in the NICP (nonideal classical plasma) is highly sensitive to both plasma and endohedral confinement. At this sensitivity, Cooper resonance character is like an encoder for fullerene structure. [ABSTRACT FROM AUTHOR]

In the present paper, we look at how the applied electric field (EF) and structure sizes affect the shallow donor impurity binding energy ( E b ), polarizability ( P α ) and photoionization cross section (PCS) of multilayer spherical quantum dots (MSQDs). The structure's wave functions and eigenvalues are calculated using the finite-element method (FEM) and in the framework of the effective mass approximation. The obtained numerical results show that the system sizes (core radius and well width) and the external EF have a considerable influence on the E b of shallow donor impurity, polarizability as well as on the dependence of the PCS on the incident photon energy. [ABSTRACT FROM AUTHOR]

In the current research, we performed a numerical investigation of a shallow donor impurity confined in a diluted magnetic semiconductor (DMS) double quantum well (DQW) made of a Cd 1 − x w Mn x w Te / Cd 1 − x b Mn x b Te under the applied electric field in the z -direction. The optoelectronic properties were carried out using the effective-mass approximation and the variational method. The binding energy and photoionization cross section were examined by considering different factors such as, well width, barrier width, impurity position, and Manganese mole fraction. Additionally, the spin polaronic shift corrections to the donor binding energy, caused by the strong exchange interaction between the magnetic moment of the Mn 2 + the confined carrier spin, have been examined under the aforementioned effects. [ABSTRACT FROM AUTHOR]

The effects of intense terahertz laser and magnetic fields on the photoionization cross section (PICS) of shallow-donor impurity in semiconductors are investigated within the Faraday configuration. The donor ground-state energy level and its wave function are calculated using a combination of nonperturbative and variational methods where radiation field is exactly included through a laser-dressed Coulomb potential (LdCP). We find that a competition between donor ground-state binding energy and optical integrals in tailoring the magnitudes and peak positions of PICS is achieved by external fields via the LdCP. In this way, the magnitudes and peak positions of PICS can be decreased or increased and effectively tuned with an appropriate choice of external fields. The overall shape of PICS is optically anisotropic, which is more pronounced in the z-polarization direction for large laser field intensity or low magnetic field. In the vicinity of ωc, the overall shape of PICS in the z-polarization direction changes into that of PICS in the x-polarization direction. Our theoretical findings hold promising applications in designing and developing new efficient impurity-based devices manipulated by external fields.

Abstract The resonance stabilized C 4 H 5 radicals (CH 3 CCCH 2 , 2-C 4 H 5 ; CH 2 CHCCH 2 , i -C 4 H 5 ; CH 3 CHCCH, 12-C 4 H 5) are among the most important precursors of benzene in hydrocarbon flames. Previous studies have revealed that i -C 4 H 5 mainly reacts with acetylene to produce fulvene which promptly transforms to benzene, while the contribution from 2-C 4 H 5 and 12-C 4 H 5 remains unclear due to the obscure composition of these isomers in flames and the lack of accurate rate constants for related reactions. In the present work, we first calculated the cross sections of the resonance stabilized C 4 H 5 radicals to quantify their composition in hydrocarbon flames (Hansen et al., 2006). The ratio of i -C 4 H 5 /(12-C 4 H 5 + 2-C 4 H 5) in the flame zone is deduced as 0.8-1.2 in fuel-rich allene, propyne, cyclopentene or benzene flames, and 2-C 4 H 5 constitutes more than 70% in the sum of 2-C 4 H 5 and 12-C 4 H 5. We further studied the reaction kinetics of 2-/12-C 4 H 5 with acetylene. Similar to i -C 4 H 5 , 2-/12-C 4 H 5 tends to produce fulvene rather than directly form benzene when reacting with acetylene. However, the reaction rates of C 2 H 2 + 2-/12-C 4 H 5 are ∼one magnitude lower than that of i -C 4 H 5 under combustion conditions. The role of the reaction between 2-/12-C 4 H 5 and acetylene is controlled by the combined effect of concentration and reaction rates. By including above computational results into kinetic modeling, we finally conclude that although the concentration of 2-/12-C 4 H 5 is comparable to that of i -C 4 H 5 , their contribution to the first aromatic ring in hydrocarbon flames from acetylene addition is limited. However, considering the noticeable concentration and the resonance stabilized structure, these species still have potential to generate aromatics. [ABSTRACT FROM AUTHOR]

This work reports on theoretical investigation of the temperature and hydrostatic pressure effects on the confined donor impurity in a AlGaAs-GaAs hollow cylindrical core-shell quantum dot. The charges are assumed to be completely confined to the interior of the shell with approximately rigid walls. Within the framework of the effective-mass approximation and by using a variational approach, we have computed the donor binding energies as a function of the shell size in order to study the behavior of the electron-impurity attraction for a very small thickness under the influence of both temperature and hydrostatic pressure. Our results show that the temperature and hydrostatic pressure have a significant influence on the impurity binding energy for large shell quantum dots. It will be shown that the binding energy is more pronounced with increasing pressure and decreasing temperature for any impurity position and quantum dot size. The photoionization cross section is also analyzed by considering only the in-plane incident radiation polarization. Its behavior is investigated as a function of photon energy for different values of pressure and temperature. The opposite effects caused by temperature and hydrostatic pressure reveal a big practical interest and offer an alternative way to tuning of correlated electron-impurity transitions in optoelectronic devices. [ABSTRACT FROM AUTHOR]

A review on the saturation technique is presented which has made utilized extensively for the absolute measurements of the photoionization cross section of the atomic excited states. This technique employed two step photoionization, in first step the state whose photoionization cross section to be measured is excited and in second step the excited state is photoionized. The energy of the exciting laser kept fixed and that of the ionizing laser is varied until the photo-ion signal gets saturated. Least square fitting of the photo-ion signals verses the ionizing laser energy density yields the photoionization cross section. Different experimental methodologies in combination with saturation technique have been employed for the measurement of photoionization cross section. These include heat cell with capacitive electrodes, atomic beam apparatus, thermionic diode ion detector, magneto optical traps (MOT), atomic beam-time of flight (TOF) mass spectrometer and DC/RF glow discharge cell. Thermionic diode ion detector and DC discharge cell offer an additional advantage of the measurement of photo absorption cross section (oscillator strength) of the atomic excited states. In addition, the availability of intense tunable dye laser made it possible to probe different region of continuum i.e. to search the regions of copper minima. [ABSTRACT FROM AUTHOR]

Within the framework of the effective-mass approximation and by using a variational method, the Stark shift of on-center and off-center donor impurity binding energies and photoionization cross section under a z -direction electric field in a prolate (oblate) core/shell ellipsoidal quantum dot has been studied. We have calculated the Stark shift as a function of the core and shell sizes and shapes, electric field, and impurity position. We also discuss the photoionization cross section as a function of photon energy with different core and shell sizes and shapes, electric field strengths, and impurity positions. The results show that the Stark shift depends strongly on the impurity position, it could be positive or negative. The core and shell sizes and shapes also have a pronounce influence on the Stark shift, and the Stark shift changes with them is non-monotonic, especially when the impurity is located at the – z -axis, the situation will become complicated. In addition, the core and shell sizes and shapes, impurity position, and electric field also have an important influence on the photoionization cross section. In particular, the photoionization cross section will vanish when the impurity is located at center of spherical core with spherical or prolate shell case at zero field. [ABSTRACT FROM AUTHOR]

We show that the theoretical predictions on high energy behavior of the photoionization cross section of fullerenes depend crucially on the form of the function V ( r ) which approximates the fullerene field. The shape of the high energy cross section is obtained without solving the wave equation. The cross section energy dependence is determined by the analytical properties of the function V ( r ) . [ABSTRACT FROM AUTHOR]

Presented here are the photoionization cross sections and parameters of the photoelectron angular distribution for atomic subshells with binding energies lower than 1.5 keV of all elements with 1 ≤ Z ≤ 100 in the photon energy range 1.5–10 keV. The calculations were performed in an effort to provide handy theoretical data for experimental studies by hard X-ray photoelectron spectroscopy (HAXPES). We used the relativistic treatment of atomic photoeffect and the Dirac–Fock method with proper consideration of the electron exchange for computing the electron wave functions. The photoionization cross sections were determined including all multipoles of the radiative field while the photoelectron angular distribution parameters were obtained within the quadrupole approximation. The effect of the hole resulting in the atomic subshell after photoionization was taken into account by the use of the frozen orbital model. [ABSTRACT FROM AUTHOR]

Hydrogen-like donor impurity states in strongly oblate ellipsoidal quantum dot have been studied. The hydrogen-like donor impurity states are investigated within the framework of variational method. The trial wave function constructed on the base of wave functions of the system without impurity. The dependence of the energy and binding energy for the ground and first excited states on the geometrical parameters of the ellipsoidal quantum dot and on the impurity position have been calculated. The behavior of the oscillator strength for different angles of incident light and geometrical parameters have been revealed. Photoionization cross-section of the electron transitions from the impurity ground state to the size-quantized ground and first excited states have been studied. The effects of impurity position and the geometrical parameters of the ellipsoidal quantum dot on the photoionization cross section dependence on the photon energy have been considered. [ABSTRACT FROM AUTHOR]