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<jats:p>Thermally activated delayed fluorescence (TADF) molecules have attracted great attention as high efficient luminescent materials. Most of TADF molecules possess small energy gap between the first singlet excited state (S<jats:sub>1</jats:sub>) and the first triplet excited state (T<jats:sub>1</jats:sub>) to favor the up-conversion from T<jats:sub>1</jats:sub> to S<jats:sub>1</jats:sub>. In this paper, a new TADF generation mechanism is revealed based on theoretical simulation. By systematic study of the light-emitting properties of SOBF-OMe in both toluene and in aggregation state, we find that the single SOBF-OMe could not realize TADF emission due to large energy gap as well as small up-conversion rates between S<jats:sub>1</jats:sub> and T<jats:sub>1</jats:sub>. Through analysis of dimers, we find that dimers with intermolecular hydrogen bond (H-bond) are responsible for the generation of TADF, since smaller energy gap between S<jats:sub>1</jats:sub> and T<jats:sub>1</jats:sub> is found and the emission wavelength is in good agreement with experimental counterpart. The emission properties of SOBF-H are also studied for comparison, which reflect the important role of H-bond. Our theoretical results agree ith experimental results well and confirm the mechanism of H-bond induced TADF.</jats:p>

<jats:p>We report elastic cross sections for low-energy electron scattering with formamide-(H<jats:sub>2</jats:sub>O)<jats:sub> <jats:italic>n</jats:italic> </jats:sub> complexes (<jats:italic>n</jats:italic> = 1, 2) in the energy region of 0.01–8 eV. The scattering calculations are performed using the <jats:italic>R</jats:italic>-matrix method in the static-exchange (SE) approximation. We consider three structures of formamide–H<jats:sub>2</jats:sub>O and six structures of formamide–(H<jats:sub>2</jats:sub>O)<jats:sub>2</jats:sub> in the present work. Our purpose is to investigate effects of water molecules hydrogen-bonding to formamide. We focus on the influence of microsolvation on the <jats:italic>π</jats:italic> <jats:sup>*</jats:sup> and <jats:italic>σ</jats:italic> <jats:sup>*</jats:sup> resonances of formamide. The scattering result for complexes shows that the position of <jats:italic>π</jats:italic> <jats:sup>*</jats:sup> resonance appears at lower or higher energies in the cluster than in the isolated formamide depending on the complex structure and the water role in the hydrogen bonding. We explain this behavior according to the net charge of the solute. It is found that the microsolvation environment has a substantial effect on the width of <jats:italic>π</jats:italic> <jats:sup>*</jats:sup> resonance. Our results indicate that surrounding water molecules may affect the lifetime of the resonances, and hence the process is driven by the anion state, such as the dissociative electron attachment.</jats:p>

<jats:p>By using the three-dimensional classical ensemble model, the recollision dynamics in nonsequential double ionization (NSDI) of Ar by 780-nm laser pulses at (6–1.2) ×10<jats:sup>14</jats:sup> W/cm<jats:sup>2</jats:sup> was extensively studied. We revealed the picture of multiple-recollision in the double ionization events at the laser intensity region below the recollision-ionization threshold. Via tracing the NSDI trajectories, it was found that the contribution of these multiple-recollision events increases as the laser intensity decreases. In this low intensity region, many multiple-recollision induced NSDI trajectories occur through the doubly excited states. The decay speed of the doubly excited state decreases with the decreasing laser intensity.</jats:p>

<jats:p>Based on a new global potential energy surface of <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{SiH}}}_{2}^{+}({{\rm{X}}}^{2}{{\rm{A}}}_{1})$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">SiH</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mi mathvariant="normal">X</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:msub> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>1</mml:mn> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_12_123403_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, the exact quantum dynamical calculation for the H(<jats:sup>2</jats:sup> S) + SiH<jats:sup>+</jats:sup>(X<jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup>) → H<jats:sub>2</jats:sub> + Si<jats:sup>+</jats:sup> reaction has been carried out by using the Chebyshev wave packet method. The initial state specified (<jats:italic>ν</jats:italic> <jats:sub>i</jats:sub> = 0, <jats:italic>j</jats:italic> <jats:sub>i</jats:sub> = 0) probabilities, integral cross sections (ICS) and thermal rate constants of the title reaction are calculated. All partial wave contributions up to <jats:italic>J</jats:italic> = 90 are calculated in exact quantum calculation including the full Coriolis coupling (CC) effect. The dynamical behaviors of probabilities, ICSs and rate constants are found to be in accord with an exothermic reaction without potential barrier. By comparing the probabilities of CC with the corresponding centrifugal sudden (CS) approximation ones, it can be concluded that neglecting CC effect will decrease the collision time, increase the amplitude of oscillation and lead to overestimation or underestimation of the reaction probability. For ICSs and rate constants, it is found that the deviation of CC and CS ICSs is small in the most of collision energy range except for the range of 0 eV–0.05 eV, while the deviation of both rate constants is considerable in the temperature range of 16 K–1000 K.</jats:p>

<jats:p>We theoretically study the stationary entanglement of two charged nanomechanical oscillators coupling via Coulomb interaction in an optomechanical system with an additional Kerr medium. We show that the degree of entanglementbetween two nanomechanical oscillators is suppressed by Kerr interaction dueto photon blockade and enhanced by Coulomb coupling strength. We also show other parameters for adjusting and obtaining entanglement, such as the driving power and the frequencies of the two oscillators, and the entanglement is robust against temperature. Our study proves a way for adjusting stationary entanglement between two optomechanical oscillators by Coulomb interaction and Kerr medium.</jats:p>

<jats:p>We demonstrate a broad gain, continuous-wave (CW) operation InP-based quantum cascade laser (QCL) emitting at 11.8 μm with a modified dual-upper-state (DAU) and diagonal transition active region design. A 3 mm cavity length, 16.5 μm average ridge wide QCL with high-reflection (HR) coatings demonstrates a maximum peak power of 1.07 W at 283 K and CW output power of 60 mW at 293 K. The device also shows a broad and dual-frequency lasing spectrum in pulsed mode and a maximum average power of 258.6 mW at 283 K. Moreover, the full width at half maximum (FWHM) of the electroluminescent spectrum measured at subthreshold current is 2.37 μm, which indicates a broad gain spectrum of the materials. The tuning range of 1.38 μm is obtained by a grating-coupled external cavity (EC) Littrow configuration, which is beneficial for gas detection.</jats:p>

<jats:p>The dependence of Brillouin gain spectrum (BGS) characteristics, including the Brillouin frequency shift (BFS) and the BGS bandwidth, on germanium concentration in large-mode-area Ge-doped passive fibers is investigated theoretically and experimentally. The simulation results show that the BFS is inversely proportional to GeO<jats:sub>2</jats:sub> concentration, and the BGS bandwidth initially increases with the augment of GeO<jats:sub>2</jats:sub> concentration, and then decreases. The BGSs of four fibers with core diameters of 10μm and 20μm for different GeO<jats:sub>2</jats:sub> concentrations are compared experimentally. Experimental results demonstrate that with the same core diameter, the variations of BFS and BGS bandwidths with GeO<jats:sub>2</jats:sub> concentration accord with the simulation results. Additionally, the BGS characteristics of three large-mode-area passive fibers with diameters of 10μm, 25μm, and 30μm are measured, which confirm that the increasing of the fiber diameters will cause the BGS bandwidth to broaden. We believe that these results can provide valuable references for modulating the high-power narrow-linewidth fiber lasers and Brillouin fiber amplifiers.</jats:p>

<jats:p>We investigate the properties of fundamental, multi-peak, and multi-peaked twisted solitons in three types of finitewaveguide lattices imprinted in photorefractive media with asymmetrical diffusion nonlinearity. Two opposite soliton self-bending signals are considered for different families of solitons. Power thresholdless fundamental and multi-peaked solitons are stable in the low power region. The existence domain of two-peaked twisted solitons can be changed by the soliton self-bending signals. When solitons tend to self-bend toward the waveguide lattice, stable two-peaked twisted solitons can be found in a larger region in the middle of their existence region. Three-peaked twisted solitons are stable in the lower (upper) cutoff region for a shallow (deep) lattice depth. Our results provide an effective guidance for revealing the soliton characteristics supported by a finite waveguide lattice with diffusive nonlocal nonlinearity.</jats:p>

<jats:p>Based on the index-induced mode coupling between the higher-order mode in core and the fundamental mode in cladding tubes, the single-mode operation can be realized in any antiresonant fibers (ARFs) when satisfying that the area ratio of cladding tube and core is about 0.46:1, and this area ratio also should be modified according to the shape and the number of cladding tubes. In the ARF with nodal core boundary, the mode in core also can couple with the mode in the wall of core boundary, which can further enhance the suppression of high-order mode. Accordingly, an ARF with conjoint semi-elliptical cladding tubes realizes a loss of higher-order mode larger than 30 dB/m; simultaneously, a loss of fundamental mode loss less than 0.4 dB/m.</jats:p>

<jats:p>We report a diode-pumped rod-type Yb:YAG laser amplifier operating at 1 kHz.Cryogenic cooling method was adopted to make the Yb:YAG crystal work with four-level behavior. A single-frequency fiber laser acts as the seed in an actively <jats:italic>Q</jats:italic>-switched Yb:YAG oscillator. The resonator delivers 5.75-mJ pulses at 1 kHz with a pulse duration of approximately 40 ns. The pulses were amplified to 61 mJ in a four-pass rod-type Yb:YAG amplifier with optical-to-optical efficiency of 24% in the main amplifier. The <jats:italic>M</jats:italic> <jats:sup>2</jats:sup> parameter of the output laser is &lt; 1.4.</jats:p>