Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>To investigate the collision processes of proton with the water dimer (H<jats:sub>2</jats:sub>O)<jats:sub>2</jats:sub> at 50 eV, the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied. Six specific collision orientations with various impact parameters are considered. The reaction channels, the mass distribution and the fragmentation mass spectrum are explored. Among all launched samples, the probability of the channel of NCT and CT is about 80%, hinting that the probability of fragmentation is about 20%. The reaction channel of PE2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions, the respective distance, the number of loss of electrons and the evolution of the electron density. The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments, the fragment with mass 36 has the highest relative abundance of 65%. The relative abundances of fragments with mass 1, 35 and 34 are 20%, 13% and 1.5%, respectively. For the total electron capture cross section, good agreement has been achieved between the present calculations and the available measurements and calculations over the energy range of 50 eV to 12 keV.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules that requires very few readily accessible input data, including the ground-state polarizability, elemental composition, ionization potential, and spin multiplicities of excited and ground states. This very simple model formulated in a semiclassical framework is based on a number of observed trends in polarizability of electronically excited compounds. To adjust the model, both accurate theoretical predictions and reliable measurements previously reported elsewhere for a broad range of multielectron species in the gas phase are utilized. For some representative compounds of general concern that have not yet attracted sufficient research interest, the results of our multireference second-order perturbation theory calculations are additionally engaged. We show that the model we developed has reasonable (given the considerable uncertainties in the reference data) accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation energy. These findings can be useful for many applications, where there is a need for inexpensive and quick assessments of the static gas-phase polarizability of excited electronic states, in particular, when building the complex nonequilibrium kinetic models to describe the observed optical refractivity (dielectric permittivity) of nonthermal reacting gas flows.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we investigate the coupled modified nonlinear Schrödinger equation. Breather solutions are constructed through the traditional Darboux transformation with the nonzero plane-wave solutions. To obtain the higher-order localized wave solution, <jats:italic>N</jats:italic>-fold generalized Darboux transformation is given. Under the condition that the characteristic equation admits a double-root, we present the expression of first-order interactional solution. Then we graphically analyze the dynamics of breather and rogue wave. Due to the simultaneous existence of nonlinear and self-steepening terms in the equation, there presents different profile in two components for the breathers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Impact of amplified spontaneous emission (ASE) noise on the stimulated Raman scattering (SRS) threshold of high-power fiber amplifiers is demonstrated numerically through a spectral evolution approach. The simulation results confirm that ASE noise among the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly. As for ASE noise originated the main amplifier, it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm. As for ASE noise originated from the seed laser, it reduces the SRS threshold at different operation wavelength on the condition that the Raman ratio is over -90 dB in the seed laser. The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-quality superconducting Ca$_{1-x}$Na$_x$Fe$_2$As$_2$ single crystals have been successfully grown by the NaAs-flux method, with sodium doping level $x$ = 0.4 - 0.64. The typical sizes of these crystals are more than 10 mm in $ab$-plane and $\sim$ 0.1 mm along $c$-axis in thickness. X-ray diffraction, resistance and magnetization measurements are carried out to characterize the quality of these crystals. While no signature of magnetic phase transitions is detected in the normal state, bulk superconductivity is found for these samples, with a sharp transition at $T_c$ ranging from 19.8 K ($x$ = 0.4) to 34.8 K ($x$ = 0.64). The doping dependence of the $c$-axis parameter and $T_c$ are consistent with previous reports, suggesting a possible connection between the lattice parameters and superconductivity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We demonstrate an experimental method for the <jats:italic>in situ</jats:italic> temperature measurement of atomic vapor using saturated absorption spectrum. By separately manipulating the frequency of pump beam and probe beam, the position of crossover peaks can move along the spectrum. Different velocity classes of atoms contribute to the crossover during the movement. We study the relationship between the intensity change of peaks and vapor temperature. Our experimental result around room temperature shows a deviation of less than 0.3 K. Compared with traditional thermometry using absorption spectroscopy, higher accuracy can theoretically be achieved for real-time thermometry.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Anisotropy is an important feature of the layered material, at which a large anisotropy is usually related to the two dimensional characteristics. We investigated the anisotropy of the layered transition metal dicalcogenide 2$H$-NbSe$_2$ at the superconducting and charge density wave (CDW) states by using magnetotransport measurements. In the superconducting state, the normalized $H_{\mathrm{c2}}^{||c}/H_p$ is independent of the thickness of 2$H$-NbSe$_2$, while $H_{\mathrm{c2}}^{||ab}/H_p$ increases significantly with decreasing the thickness, where $H_p$ is the Pauli limiting magnetic field, and $H_{\mathrm{c2}}^{||c}$ and $H_{\mathrm{c2}}^{||ab}$ are the upper critical field at $c$ and $ab$ directions, respectively. It is found that the superconducting anisotropy parameter $\gamma_{Hc2}=H_{\mathrm{c2}}^{||ab}/H_{\mathrm{c2}}^{||c}$ increases with reducing the thickness of 2$H$-NbSe$_2$. %from 4.65 in the bulk sample to 17.7 in the ultrathin sample ($5-10$ layers). In the CDW state, the angular ($\theta$) dependent of magnetoresistance $R(H,\theta)$ scales with $H(\cos^2\theta+\gamma_{CDW}^{-2}\sin^2\theta)^{1/2}$, which decreases with increasing the temperature and disappears at about 40 K. It is found that the CDW anisotropy parameter $\gamma_{CDW}$ is much larger than the effective mass anisotropy but does not change a lot for the ultrathin and bulk samples. Our results suggest the three-dimensional superconductivity and quasi-two dimensional CDW in the bulk 2$H$-NbSe$_2$.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The electron transport layer (ETL) plays an important role on the performance and stability of perovskite solar cells (PSCs). Developing double ETL is a promising strategy to take the advantages of different ETL materials and avoid their drawbacks. Here, an ultrathin SnO<jats:sub>2</jats:sub> layer of ~ 5 nm deposited by atomic layer deposit (ALD) was used to construct a TiO<jats:sub>2</jats:sub>/SnO<jats:sub>2</jats:sub> double ETL, improving the power conversion efficiency (PCE) from 18.02% to 21.13%. The ultrathin SnO<jats:sub>2</jats:sub> layer enhances the electrical conductivity of the double layer ETLs and improves band alignment at the ETL/perovskite interface, promoting charge extraction and transfer. The ultrathin SnO<jats:sub>2</jats:sub> layer also passivates the ETL/perovskite interface, suppressing nonradiative recombination. The double ETL achieves outstanding stability compared with PSCs with TiO<jats:sub>2</jats:sub> only ETL. The PSCs with double ETL retains 85% of its initial PCE after 900 hours illumination. Our work demonstrates the prospects of using ultrathin metal oxide to construct double ETL for high-performance PSCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This research argues that using an electron beam with high kinetic energy to pump perovskite quantum dots can significantly boost the efficiency of low-frequency photon radiation conversion. Firstly, we measure the random lasing threshold and luminescence threshold of CsPbX<jats:sub>3</jats:sub> films pumped by an electron beam. Then, we simulate the spatial distribution of electron beams in CsPbX<jats:sub>3</jats:sub> films. Combined with the above data, a low-frequency photon radiation conversion model based on electron pumped perovskite quantum dots is presented. This could be a way to create a terahertz source with a high-power output or to multiply terahertz power.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This study demonstrated the influence of Ag<jats:sup>+</jats:sup>/PO<jats:sub>4</jats:sub> <jats:sup>3-</jats:sup> ratio in precursor solution on the crystal structural formation, morphology, physical properties, and photocatalytic performance of Ag<jats:sub>3</jats:sub>PO<jats:sub>4</jats:sub> photocatalyst fabricated by facile precipitation method from AgNO<jats:sub>3</jats:sub> and Na<jats:sub>2</jats:sub>HPO<jats:sub>4</jats:sub>.12H<jats:sub>2</jats:sub>O. The material characterizations were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR) absorption, Raman scattering, X-ray photoelectron spectroscopy (XPS), UV-vis absorption, and photoluminescence (PL). The results show that Ag<jats:sub>3</jats:sub>PO<jats:sub>4</jats:sub> crystallizes better when the excess PO<jats:sub>4</jats:sub> <jats:sup>3-</jats:sup> content increases, the lattice parameters decrease slightly while the crystal diameter and the particle size increase. This change is also observed in the Raman scattering and FTIR spectra with the increase in the vibration frequency of the [PO<jats:sub>4</jats:sub>] group. The compression of the [PO<jats:sub>4</jats:sub>] unit was also confirmed in the XPS spectra with the shift of P 2p peaks toward to higher binding energy. The photocatalytic results showed that the samples synthesized from excess PO<jats:sub>4</jats:sub> <jats:sup>3-</jats:sup> solution exhibited higher photocatalytic performance comparing to sample with Ag<jats:sup>+</jats:sup>/PO<jats:sub>4</jats:sub> <jats:sup>3-</jats:sup> ratio of 3:1. Sample prepared from the precursor solution with Ag<jats:sup>+</jats:sup>/PO<jats:sub>4</jats:sub> <jats:sup>3-</jats:sup> ratio of 3:1.5 was optimal for RhB decomposition under both visible light and natural sunlight, completely decomposing RhB 10 ppm after 15 minutes of Xenon lamp irradiation and after 60 minutes under solar light irradiation. This is attributed to the high crystallinity, small particle size and low electron-hole recombination rate of sample.</jats:p>