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Radiative transition probabilities between low-lying electronic states of N <sub/>2</sub>
摘要： This work mainly investigates the transition dipole moments (TDMs) and radiative transition probabilities of dipole-allowed transitions between the b1Σu+, a''1Σg+, 13Σg-, 23Σg-, C'3Σu+, B'3Σu-, W3Δu, 23Σu+ and H3Υu states of N2. Many of these transition properties are previously unknown. For completeness, another 14 electronic states that correlate to four lowest dissociation limits are also calculated. The potential energy curves (PECs) are calculated at the valence internally contracted multireference configuration-interaction (icMRCI) level of theory, along with the Davidson correction, the core-valence (CV) correction and the scalar relativistic correction, as well as the basis-set extrapolation. These corrections, especially the CV correction, greatly improve the accuracy of the PECs, as shown by the excellent agreement of the fitted spectroscopic parameters with the available experimental data. In order to verify the accuracy of transition properties, we calculate the Einstein coefficients of the extensively studied B3Σg- - A3Σu+, C3Σu+ - B3Σg-, W3Δu - B3Σg-, B'3Σu- - B3Σg-, C'3Σu+ - B3Σg-, w1Δu - a1Σg+, a1Σg+ - a'1Σg- and b1Σu+ - X1Σg+ band transition systems and compute the radiative lifetimes of N2 B3Σg-, C3Σu+ and W3Δu states, which are in good agreement with the experimental data. Similar accuracy can be assumed for the previously undetermined 13Σg- - B'3Σu-, 23Σg- - B'3Σu-, 23Σg- - C'3Σu+, 23Σu+ - B3Σg- and b1Σu+ - a''1Σg+ band transition systems. The large Einstein coefficients of these band systems can provide guidelines for observing such newly predicted band transitions in the appropriate spectroscopy experiments.
关键词： radiative lifetime,Spectroscopic parameter,radiative transition probability,transition dipole moment,N2
更新于2025-09-23 15:23:52
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Electronic transition dipole moment and radiative lifetime calculations of lithium dimer ion-pair states
摘要： We present here a computational study of the lifetimes of the ion-pair n1Rt g , n = 3–6, states of lithium dimer. The lifetimes are calculated using ab initio electronic transition dipole moment functions and combination of experimental and ab initio potential curves. The ab initio calculations are carried out using the full configuration-interaction method. The lifetime calculations include the radiative contributions of all the allowed bound–bound and bound-free transitions to lower electronic states. In addition, to test the computational methods used in this work, we have calculated the lifetimes of levels of the lowest excited singlet, A1Rt u , state of lithium dimer.
关键词： Electronic transition dipole moment,Lithium dimer,Lifetime,Ion-pair states
更新于2025-09-23 15:22:29
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Simple molecular-engineering approach for enhancing orientation and out-coupling efficiency of thermally activated delayed fluorescent emitters without red-shifting emission
摘要： The inclusion of a tetraphenylbenzene (4Ph) unit in thermally activated delayed fluorescence (TADF) emitters is demonstrated as a novel strategy for greatly enhancing the horizontally oriented alignment of the emitters without shifting the emission spectrum to longer wavelengths. Doping of blue-emitting 4PhOXDDMAC or greenish-blue-emitting 4PhOXDPXZ into o-DiCbzBz host layers yielded much higher degrees of horizontally oriented alignment for the emitter (up to 92%) compared to when the 4Ph unit was excluded (69% and 75%, respectively). The enhanced alignment results in high out-coupling efficiencies of 24% and 35% in organic light-emitting diodes based on 4PhOXDDMAC and 4PhOXDPXZ, respectively, and boosts the external quantum efficiencies to values (8.8% and 29.2%, respectively) that are higher than would be expected for randomly oriented emitters (out-coupling efficiency of 20%). These enhancements are achieved while avoiding the red-shift that often occurs using the common strategy of increasing molecular length, and, thereby, conjugation, to increase orientation.
关键词： transition dipole moment,thermally activated delayed fluorescence,light out-coupling factor,molecular orientation,organic light-emitting diodes
更新于2025-09-23 15:21:21
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High-resolution cw-cavity ring-down spectroscopy of allowed (??4??+????5)0 and forbidden (??4??+????5)2 bands of C2H2 using external-cavity quantum cascade laser
摘要： In this paper, we measured the absolute line intensities and air broadening coefficients of several rotationally resolved lines in the P and R branches of the allowed (ν4+ν5)0 and forbidden (ν4+ν5)2 vibrational combinational bands of C2H2 at room temperature 296K. These measurements were performed using an external-cavity quantum cascade laser (EC-QCL) operating at 7.5 μm coupled with high-sensitive cavity ring-down spectroscopy (CRDS). Rotational level-dependent pressure-broadening coefficients of the resolved spectral lines of the selected transitions from (ν4+ν5)0 band are reported here. The air broadening coefficients for 5 rotational lines from P-branch of (ν4+ν5)2 band were also obtained first time with better than 3% uncertainty. The vibrational transition dipole moment squared values of the rotational lines and empirical Herman-Wallis coefficients were also quantified from experimental data. Finally, experimentally obtained all spectroscopic parameters were rigorously compared with previous studies. The new experimental data including several spectroscopic parameters will be useful for atmospheric and astrophysics applications.
关键词： Cavity ring-down spectroscopy,Absolute measurement of line intensities and air broadening coefficients,Transition dipole moment,Ro-vibrational allowed and forbidden transition,Quantum cascade laser,Infrared spectra of Acetylene
更新于2025-09-23 15:21:01
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Cooper minimum of high-order harmonic spectra from an MgO crystal in an ultrashort laser pulse
摘要： Cooper minimum structure of high-order harmonic spectra from atoms or molecules has been extensively studied. In this paper, we demonstrate that the crystal harmonic spectra from an ultrashort midinfrared laser pulse also exhibit the Cooper minimum characteristic. Based on the accurate band dispersion and k-dependent transition dipole moment (TDM) from the ?rst-principles calculations, it can be found that the harmonic spectra from the MgO crystal along the (cid:2)-X direction present a dip structure in the plateau, which is originated from the valley of TDM by examining the distribution of the harmonic intensity at the k space. The Cooper minimum feature in crystal high-order-harmonic generation (HHG) will pave a new way to retrieve the band information of solid materials by using HHG from the ultrashort midinfrared laser pulse.
关键词： transition dipole moment,ultrashort laser pulse,Cooper minimum,MgO crystal,high-order harmonic generation
更新于2025-09-23 15:21:01
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Deep Learning for Optoelectronic Properties of Organic Semiconductors
摘要： Atomistic modeling of the optoelectronic properties of organic semiconductors (OSCs) requires a large number of excited-state electronic-structure calculations, a computationally daunting task for many OSC applications. In this work, we advocate the use of deep learning to address this challenge and demonstrate that state-of-the-art deep neural networks (DNNs) are capable of accurately predicting various electronic properties of an important class of OSCs, i.e., oligothiophenes (OTs), including their HOMO and LUMO energies, excited-state energies and associated transition dipole moments. Among the tested DNNs, SchNet shows the best performance for OTs of different sizes, achieving average prediction errors in the range of 20-80meV. We show that SchNet also consistently outperforms shallow feed-forward neural networks, especially in difficult cases with large molecules or limited training data. We further show that SchNet could predict the transition dipole moment accurately, a task previously known to be difficult for feed-forward neural networks, and we ascribe the relatively large errors in transition dipole prediction seen for some OT configurations to the charge-transfer character of their excited states. Finally, we demonstrate the effectiveness of SchNet by modeling the UV-Vis absorption spectra of OTs in dichloromethane and a good agreement is observed between the calculated and experimental spectra.
关键词： optoelectronic properties,organic semiconductors,transition dipole moment,SchNet,oligothiophenes,deep learning,UV-Vis absorption spectra
更新于2025-09-23 15:19:57
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Orientation‐Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： transition dipole moment,Cocrystal,polymorphs,two-dimensional photonics,anisotropic optical waveguides
更新于2025-09-16 10:30:52
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Morphology‐Dependent Luminescence and Optical Waveguide Property in Large‐Size Organic Charge Transfer Cocrystals with Anisotropic Spatial Distribution of Transition Dipole Moment
摘要： Organic cocrystals exhibiting active optical waveguide behaviors are strongly related to the total internal reflection, molecule stacking modes, and the spatial distribution of transition dipole moment (μ) in crystals. However, organic charge transfer (CT) cocrystals as new materials that exhibit optical waveguide property responses to anisotropic spatial distribution of μ are still unknown. Herein, prepared is a novel organic CT cocrystal 9AC-TCNB (9AC = 9-anthracene carboxylic acid, TCNB = 1,2,4,5-tetracyanobenzene) with a mixed stacking structure of donor (D) and acceptor (A) along two different orientations on the same lattice plane. According to various spectroscopic analyses, two direction-oriented asymmetric light propagate in the cocrystal derived from the anisotropic spatial distribution of μ have been confirmed. Photo luminescence (PL) microscopic images and spatial resolution PL spectra of 1D and 2D 9AC-TCNB cocrystals further demonstrate that the CT cocrystals possess morphology and color-dependent optical waveguide properties with anisotropy, which confirms the principle theory of light propagation. This result can open new potential applications of organic cocrystals in large-scale optical waveguide devices and integrated optics.
关键词： large-size organic cocrystals,charge transfer,optical waveguide,transition dipole moment
更新于2025-09-12 10:27:22
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Orientation-Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： two-dimensional photonics,anisotropic optical waveguides,Cocrystal,polymorphs,transition dipole moment
更新于2025-09-12 10:27:22
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Theoretical study on the low-lying electronic excited states and laser cooling feasibility of AuH molecule
摘要： To evaluate characteristics of the low-lying electronic states and the feasibility of the laser cooling of the AuH molecule, we investigate the potential energy curves (PECs), the vibrational and rotational characteristics of the ground and low-lying excited electronic states based on ab initio calculations. The PECs of the X1Σ+, A1Σ+, B1Σ+, a3Σ+, b3Σ+, e3Σ+, C1П, D1П, c3П and d3П states and the transition dipole moments among these states are calculated with the multi-reference configuration interaction method with Davidson correction and all-electron basis sets. Based on the obtained PECs, the Schr?dinger equations of nuclear movement are solved to obtain the rotational and vibrational energy levels of the electronic states. The spectroscopic parameters are obtained by fitting the obtained rotational and vibrational levels with Dunham series expansion. The matrices of the Franck-Condon factors (FCFs) dependent on the vibrational quantum numbers are obtained. The feasibility of laser cooling is explored. The FCF of the D1П (v′ = 0) ? X1Σ+ (v″ = 0) transition is 0.9862, which implies that the AuH molecule is feasible but not the much better ones for laser cooling and more pumping lasers are needed. The optical laser cooling scheme is suggested and the Einstein coefficient and the recoil temperature are calculated to evaluate the effect of the cooling scheme.
关键词： Franck-Condon factor,recoil temperature,laser cooling scheme,transition dipole moment,low-lying excited states
更新于2025-09-11 14:15:04