Vibronic effect study of ^(1)A_(2) state of H_(2)O and D_(2)O

The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effect.It is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer region.The present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.

Determination of Coordination Configuration of Rare Earth Ions with Aminoacids in Solutions with Cooperative Vibronic Spectroscopy

The use of cooperative vibronic spectroscopy to measure coordination numbers of the ligands surrounding rare earth ions in solutions was proposed and demonstrated. It is shown that the time-resolved cooperative vibronic spectroscopy is a very useful technique for the determination of the ligand type and ligand number for different coordination groups. Coordination configuration of arginine with Tb3+ in solutions with different pH values was studied. It demonstrates that the carboxy1 of arginine can replace H2O to coordinate with Tb3+ and the coordination number of carboxyl increases with the increase of pH value of the solutions.

DFT Study on Structural Distortion and Vibronic Coupling of Vanadyl Porphyrin Anion and Cation

The geometries of one-electron reduced/oxidized species （[TOP]-/[VOP] ＋） of vanadyl por- phyrin （VOP） have been calculated with PBE1PBE method. The results show that for both [VOP]- and [VOP]＋ the ground states are triplet, in which one of the two unpaired electron occupies the dxy orbital of the V atom while the other occupies the n-orbital of porphyrin ring. Thus both [VOP]- and [VOP]＋ can be considered as n-radicals. The ground state of neutral VOP molecule is doublet with the unpaired electron occupying dxy orbital of V atom. In contract to the C4v symmetry of neutral VOP molecule, [VOP]- anion has a ＂rectangular＂ distorted C2v structure due to Jahn-Teller effect. The linear vibronic coupling constants for the Jahn-Teller active modes of [TOP]- were evaluated and the node patterns of frontier KS orbitals are used to explain the reason why the distortion occurs along specific modes. The ground state [VOP]＋ has a porphyrin ring with pronounced bond length alternation due to pseudo-Jahn-Teller effect, causing its symmetry declined from C4v to Ca. The bond length alternation is well explained with the node patterns of re-constructed frontier KS orbitals.

Multiphonon-assisted continuous-wave tunable vibronic laser in Yb:LuScO_(3)crystal

In this work,we demonstrate the phonon-assisted vibronic lasing of a Yb-doped sesquioxide Yb:LuScO_(3)crystal.The electron–phonon coupling process was analyzed and the Huang-Rhys factor S was calculated to be 0.75 associated with the fluorescence spectrum at room temperature.By a rational cavity design to suppress lasing below 1100 nm,a continuously spectral tunability from 1121 to 1136 nm was realized in a Yb:LuScO_(3)laser,which represents the longest achievable wavelength in the Yb-doped sesquioxide lasers.Moreover,the Raman spectrum indicated that the Egphonon mode with a frequency of 472 cm^(-1)was mainly devoted to the phonon-assisted transition process.This work broadens the achievable laser spectrum of Yb-doped sesquioxide,and suggests that the multiphonon–electron coupling strategy should be universal for other laser materials.

Determination of coordination environment of rare earth ions with cooperative vibronic spectroscopy

WITH the explosion of world population, food has become a crucial problem already. It

Charge-Transfer and SERS Coupling on TiO2

We report the SERS enhancements of Raman forbidden surface modes of TiO2 in different sized TiO2 crystals. This current study utilizes the relationship between the vibronic coupling and the degree of charge-transfer to explain the differences of Surface Enhanced Raman Scattering (SERS) enhancements. Our study shows a direct correlation between the degree of charge-transfer and vibronic coupling. This relationship suggests that charge-transfer between the N-719 dye and TiO2 due to vibronic coupling plays a fundamental role in SERS enhancements. Furthermore, this study shows a strong dependence of the enhancements of the N-719 dye molecular modes to that of the surface modes. This indicates that the mechanism that governs the enhancements of the surface modes in TiO2 crystals most likely also dictates the enhancements of the N-719 dyes.

Long-Lived Coherence Originating from Electronic-Vibrational Couplings in Light-Harvesting Complexes

We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear photon echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same system, the coherence time and relaxation time of excitonic states are short, however, if the couplings of electronic and intra-pigment vibrational modes are considered, the coherence time and relaxation time of this vibronic states are greatly extended. It means that the couplings between electronic and vibrational modes play important roles in keeping long-lived coherence in light-harvesting complexes. Particularly, by using the method we can fix the transition path of the energy transfer in bio-molecular systems.

Pseudo Jahn-Teller Effect in Puckering and Planarization of Heterocyclic Compounds

The goal of this brief partly review paper is to summarize the results of the works published over the last few years regarding the origin of the out-of-plane distortions (puckering) of heterocyclic compounds. In all the papers devoted to this problem, it is shown that the instability of planar configurations of heterocyclic molecules leading to symmetry breaking and distortions is induced by the pseudo Jahn-Teller effect (PJTE). Special attention in this work is paid to the mechanism of suppression and enhancement of the PJTE distortions of heterocycles by oxidation, reduction, and chemical substitutions. It is demonstrated that oxidation of 1,4-dithiine containing compounds leads to suppression of the PJTE and to restoration of their planar nuclear configurations. An example of a dibenzo[1,2]dithiine molecule is used to demonstrate the mechanism of enhancement of the PJTE by reduction. It is shown that the reduction of the neutral C12H8S2 molecule up to the dianion (C12H8S2)2- enhances the PJTE, followed by the S-S bond cleavage and significant structural distortions of the system. The change of the PJTE by chemical substitutions, accompanied either by puckering or by planarization of heterocyclic compounds, is discussed using as examples 1,4-ditinine and its S-oxygenated derivatives.

The vibron dressing in α-helicoidal macromolecular chains

We present a study of the physical properties of the vibrational excitation in α-helicoidal macromolecular chains, caused by the interaction with acoustical and optical phonon modes. The influence of the temperature and the basic system parameters on the vibron dressing have been analyzed by employing the simple mean-field approach based on the variational extension of the Lang-Firsov unitary transformation. The applied approach predicts a region in system parameter space where one has an abrupt transition from a partially dressed （light and mobile） to a fully dressed （immobile） vibron state. We found that the boundary of this region depends on system temperature and the type of bond among structural elements in the macromolecular chain.

Transitional Description of Diatomic Molecules in U（4） Vibron Model

U(3)-O(4) transitional description of diatomic molecules in the U(4) vibron model is studied by usingthe algebraic Bethe ansatz, in which the O(4) limit is a special case of the theory. Vibrational band-heads of sometypical diatomic molecules are fitted by both transitional theory and the O(4) limit within the same framework. Theresults show that there are evident deviations from the O(4) limit in description of vibrational spectra of some diatomicmolecules.

Selective conformer detection of short-lived base pair tautomers: A computational study of the unusual guanine-cytosine pairs using ultrafast resonance Raman spectroscopy

Base pair mismatch has been regarded as the main source of DNA point mutations, where minor shortlived tautomers were usually involved. However, the detection and characterization of these unnatural species pose challenges to existing techniques. Here, by using systematic structural and ultrafast resonance Raman(RR) spectral analysis for the four possible conformers of guanine-cytosine base pairs, the prominent marker Raman bands were identified. We found that the hydrogen bonding vibrational region from 2300 cm^(-1) to 3700 cm^(-1) is ideal for the identification of these short live species. The marker bands provide direct evidence for the existence of the tautomer species, thus offering an effective strategy to detect the short-lived minor species. Ultrafast resonance Raman spectroscopy would be a powerful tool to provide direct evidence of critical dynamical details of complex systems involving protonation or tautomerization.

Observation of electron–phonon coupling and linear dichroism in PL spectra of ultra-small CsPbBr_(3) nanoparticle solution

Blue-emission(~480 nm)CsPbBr_(3) nanoparticles with ultra-small size(~2.1 nm)are synthesized using the liquid nitrogen freezing with the ligand of dodecylbenzene sulfonic acid(DBSA).Asymmetric narrow emissions at the low energy side,with the full width at half-maximum of~20 nm,are observed in solution and film at room temperature.The spectral asymmetry is mainly ascribed to phonon vibronic replica with averaged phonon energy of~40 meV.Moreover,exciting this CsPbBr_(3) nanoparticles solution using linearly polarized 6 ns pulsed laser at 355 nm,we observe polarized emission with polarization degree(P_(PL))of~7%,and P_(PL) decreases more than 20%in the vibronic progression.However,the P_(PL) goes to zero in frozen solutions as well as in films.Thus we speculate the polarized emission is due to the photoinduced re-alignment of nanoparticles,and the diminished P_(PL) at the phonon side band may be due to the non-adiabatic electronic-to-vibronic transitions.The novel phenomena from the ultra-small CsPbBr_(3) nanoparticle demonstrated in this work may provide fundamental insights into its photophysics with direct implications for optoelectronics.

Investigation of electronic excited states in single-molecule junctions

The investigation of electronic excited states in single-molecule junctions not only provides platforms to reveal the photophysical and photochemical processes at the molecular level,but also brings opportunities for the development of single-molecule optoelectronic devices.Understanding the interaction mechanisms between molecules and nanocavities is essential to obtain ondemand properties in devices by artificial design,since molecules in junctions exhibit unique behaviors of excited states benefited from the structures of metallic nanocavities.Here,we review the excitation mechanisms involved in the interplay between molecules and plasmonic nanocavities,and reveal the influence of nanostructures on excited-state properties by demonstrating the differences in excited state decay processes.Furthermore,vibronic transitions of molecules between nanoelectrodes are also discussed,offering a new single-molecule characterization method.Finally,we provide the potential applications and challenges in single-molecule optoelectronic devices and the possible directions in exploring the underlying mechanisms of photophysical and photochemical processes.

Theoretical Simulation of the Vibrationally Resolved UV Absorption Spectrum of Acryloyl Fluoride

Acryloyl fluoride is an ideal molecule for investigating the phenomenon of hindered internal rotation.In concert with recently acquired high-resolution UV absorption spectrum of acryloyl fluoride,in this study,the absorption spectra of the s-trans and s-cis isomers of acryloyl fluoride were theoretically simulated.The simulated spectra were convoluted by a Gaussian function with displacement,distortion,Franck-Condon,Herzberg-Teller,and Duschinsky effects in the framework of the time-independent model.The statistical vibronic transition analysis reveals the unity of the spectrum transition property,the relevant normal modes,and the primary geometrical variations,enriching the understanding of the experimental observation.The discrepancy between the theoretical and experimental spectra was interpreted clearly.