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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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Study of the Electronic and Electrical Properties of the C60F18 Polar Molecule on Au(111) Surface
摘要： For adequate description of the adsorption and self-assembly of C60F18 polar molecules on the surface Au(111), quantum-chemical studies of the electronic and electrical properties of a single molecule are performed. Using various procedures of density functional theory, the electric dipole moment of the molecule, distributions of the electrostatic potential, electric-field magnitude and electron density are calculated with controlled accuracy for the first time. An improved value of the electric dipole moment of the C60F18 molecule is obtained in a range from 10 to 11 D. The known approximation of a point dipole for electric-field strength is shown to be fulfilled within an accuracy of 30% even at distances twice greater than the size of the molecule. The structural fragments of the calculated lowest unoccupied and highest occupied molecular orbitals are assigned to their images, which were previously obtained using scanning tunneling microscopy and spectroscopy.
关键词： density functional theory,lowest unoccupied and highest occupied molecular orbitals,electric dipole moment,scanning tunneling spectroscopy,fullerene fluoride
更新于2025-09-23 15:23:52
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Low-frequency dielectric spectroscopy and distinct relaxation modes in smectic phases of liquid crystal dimers
摘要： Low-Frequency (LF~20Hz–10MHz) ac field response and relaxation modes are investigated in layered liquid crystalline (LC) smectic phases exhibited by Hydrogen bonded dimers, viz., nOnBA:MA:nOBA’s with sort spacer moiety and long flexible end chains for n=10,11 and 12. Permittivity (ε') and loss (ε'') determined from capacitance and loss factor. Phase transition temperatures (Tc) are determined. Intra-molecular aromatic interaction and storage capacity are evinced by hysteresis behavior. Data of loss ε''(ω) and permittivity ε'r(ω) recorded in smectic phases infers non-Debye type of asymmetric dispersion. Multiple loss peaks in ε''(ω) is argued to involve distinct time scaled relaxations. Relaxation analyzed by Cole-Davidson method. Re-orientation of longitudinal dipole moment μ to the field analyzed. μ is resolved by rigid core, intra-molecular repulsive and flexible end-chain components. Observed distinct time scale response confirms dipolar components. Trends of relaxation frequency, activation energy, loss maxima, dielectric strength and distribution parameter are analyzed in device perspective. Relaxation and order director fluctuations analyzed. ODF suggest the device utility in high temperature smectic phases far away from critical fluctuations.
关键词： Order Director Fluctuations,Relaxation,Permittivity,Resolved dipole moment,Activation energy,Reorientation,Loss
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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Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations
摘要： Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.
关键词： defects,lithium niobate,dipole moment,spontaneous polarization
更新于2025-09-23 15:22:29
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Solvent effects on the absorption and fluorescence spectra of Zaleplon: Determination of ground and excited state dipole moments
摘要： Solvent effects on the absorption and fluorescence spectra of Zaleplon, a nonbenzodiazepine sedative/hypnotic drug that is mainly used for the short term treatment of insomnia, were investigated in 18 different solvents with diverse polarities. Dipole moments of the ground and excited state (μg and μe) were determined by Lippert–Mataga, Bakhshiev, Reichardt, McRae and Suppan solvatochromic methods. The dipole moment of Zaleplon ground state in the gas phase has been calculated as μg = 10.95 D (TD-DFT) with B3LYP/cc-pVTZ functional. There is a good agreement of theoretical data with Reichardt, McRae, and Suppan correlations, while some dissidence with Lippert–Mataga and Bakhshiev equations is suggesting the occurrence of specific solute–solvent interactions. Additionally, multiple linear regression analyses with Kamlet–Taft and Catalan solvatochromic models was applied to solute–solvent interactions. Dominant property of the solvent that affects the absorption band and Stokes shifts of Zaleplon is polarity of the solvent while the emission band is influenced mainly by solvent basicity.
关键词： Solvatochromic methods,Dipole moment,Stokes shift,MLR analysis,Zaleplon
更新于2025-09-23 15:22:29
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Time Domain Modelling of Pulse Wave Scattering on Small Metal Spheres
摘要： We consider a short pulse plane wave incident on a small metal sphere. The scattered field from the sphere can be presented as a multipole expansion over spherical harmonics. For small spheres (compared to the signal duration) the scattered field will be mainly presented by the dipole component. So we find in a closed form and analyze the convolution operator that relates the induced dipole moment (both electric and magnetic dipoles are considered) to the incident electric field waveform. The numerical approach to calculate scattering from several such spheres is described.
关键词： transient electric dipole,discrete dipole approximation,induced dipole moment,closed-form solution,transient diffraction
更新于2025-09-23 15:21:21
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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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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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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