Electron transfer dynamics in the excited state studied by stochastic-Liouville equation

Electron transfer dynamics in the excited state is theoretically investigated by means of the stoschastic-Liouville equation. We evaluate time dependence of the density matrix for the three electronic states, the ground state, locally excited state, and the charge transfer state by solving the equation numerically. We treat the optical transition and electronic interaction in the excited states quantum mechanically to investigate these effects on the reaction dynamics.     

Impact of the Vibrationally Excited States on the Macroscopic Behaviour of the Band-like Electron Beam Discharge Plasma in H/H2-Mixture

The investigation of the impact of the vibrationally excited molecules in the electronic ground state was performed by simultaneously solving a balance equation system for the main charge carriers, the H atoms, the metastable H atoms, the H₂ molecules in the different vibrational states and for the power transfer of the electrons in the beam discharge mixture plasma. The balance equations for the vibrational states include in particular one-quantum step excitation and deexcitation, electronic excitation, dissociation and ionization from each vibrational level in electron collisions as well as the finite life time of these states because of the gas transfer through the band-like plasma. A main finding is that due to the additional impact of vibrationally excited molecules there is a marked enhancement of the resulting dissociation and ionization degree in the beam discharge plasma at medium power input from the turbulent electric field. For discharge parameters of practical interest the ionization and dissociation budget, the population of the vibrational states, the different energy dissipation processes and the energy pumping into the ladder of the vibrational states were calculated and discussed in detail.     

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part II: Theoretical investigation of oxalyl chloride

The structures of the oxalyl chloride molecule (COCl)₂ in the ground and the four lowest (two singlet and two triplet) excited electronic states were investigated by means of the CASPT2(8-6)/cc-pVTZ technique. The equilibrium geometric parameters, harmonic vibrational frequencies, and adiabatic energies of the electronic transitions were determined for all states under investigation. The calculations predicted the existence of the trans- and gauche- conformers in the ground state and the trans- and cis-conformers in all excited states. For the ground electronic state, the conformer energy difference and the barriers to conformational transitions were estimated using extrapolation to the complete basis set within a Valence Focal-Point Analysis procedure. The internal rotation in the excited electronic states was found to be strongly coupled with the non-planar symmetric CCOCl wagging. Two-dimensional potential energy surface sections along internal rotation and non-planar coordinates were constructed, and the corresponding anharmonic vibrational problems for the trans-conformer were solved.     

飞秒激光控制的分子量子动力学研究：(Ⅰ)三维二能级系统

结合MCDTDH方法和优化控制理论，以吡嗪分子为例，模拟了在给定不同的目标态下具有3个振动模两个电子态的分子系统的量子动力学过程. 以电子激发态作为目标态，优化激光场为一个楔形脉冲，它所激发的电子波函数在两个调制模空间中振荡最后达到平衡位置，并有较高的目标态产生率.发现目标态的选择强烈地影响波函数随时间的演变情况，若目标态在各个模的平衡位置，在优化激光场的作用下，电子波函数被直接激发到其平衡位置；若目标态不在振动模的平衡位形，其电子波函数经过强烈的振荡以达到平衡态. 关键词： 优化控制 MCTDH 方法 分子量子动力学     

Br_2分子在360—610 nm的光解离动力学研究

利用包含转动自由度在内的含时薛定谔方程研究了Br_2分子在波长范围为360—610 nm的光解离动力学.通过计算得到了Br_2分子在四个特征波长处的切片解离影像,并经过分析得到了与切片解离影像相对应的动能分布;计算了Br_2分子在波长范围为360—610 nm内总的动能分布,以及从A,B和C三个电子态解离的碎片各自所对应的动能分布;计算了A,B和C三个电子态各自的解离概率以及碎片产物的分支比Γ(Br~*/(Br+Br~*))随波长的变化.     

Energy and Electron Transfer in the Field of Transition Metal Complexes

The bimolecular quenching of an excited state molecule in fluid solution can occur in three fundamental ways:^1–3 (i) chemical reaction between the excited state and the quencher, (ii) electronic energy transfer from the excited state to the quencher, or (iii) deactivation of the excited state by some catalytic action of the quencher. The intimate nature of the quenching mechanism is often difficult to elucidate for a single excited state-quencher couple. More useful information can generally be obtained from correlations of data concerning homogeneous families of excited states and/or quenchers.     

Extension of the Local Approach to excited states of molecules

The Local Approach for the calculation of electronic correlation energies in molecules is generalized to excited states. Within the Local Approach correlated states are obtained by applying a local projection operator on the Hartree-Fock ground state or simple reference states, which are used as zeroth order approximations for the excited states, respectively. In the case of excited states one has in addition to require the correlated states to be orthogonal on the states lower in energy. This is done by using Schmidt's orthogonalization. The method is applied to a simple model of the H₆-ring for which an exact solution is available. The results obtained are of comparable quality as for the ground state.     

The single-determinant approximation with a local potential for excited states

The specific features of the calculations of the electronic structure in the approximation of a local exchange potential that is identical for all the electrons involved are considered. An optimized effective potential method is proposed for calculating the energies of excited electronic states of the same symmetry. A single-particle Schrö dinger equation is derived for an excited state whose orbitals are described by a single-determinant wave function orthogonal to the ground state. The equations determining the local potential for excited states are obtained within the variational approach. The solution to these equations is analyzed in the framework of the parameterized representation of the effective potential. The efficiency of the proposed method is demonstrated by calculating the energies of three excited states of the same symmetry for a HeH molecule. The difference between the results obtained by the Hartree-Fock method and the method proposed in this paper is equal, on average, to 0.05%. A comparison with the results obtained from precise calculations based on the configuration interaction method shows that the accuracy in determining the energy of the excited states by the optimized effective potential method is comparable to the accuracy in calculating the energy of the ground state.     

Theory of the resonance electronic Raman effect

The behaviour of electronic Raman scattering, excited under resonance conditions, is discussed in relation to molecular properties of the ground electronic state, the resonant excited state and the final electronic state. It is shown how the intensity distribution within vibronically structured electronic Raman bands depends on differences of molecular geometry and force field between these states.     

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part III: Theoretical investigation of oxalyl fluoride

We present a theoretical investigation of oxalyl fluoride (COF)₂ in the ground and the four lowest excited (two singlet and two triplet) electronic states of the n,π∗-type mainly with the CASPT2(8-6)/cc-pVTZ method. Geometries, vibrational frequencies, potential energy functions of internal rotation, and adiabatic electronic transition energies were obtained. The conformer energy difference and the barrier to internal rotation in the ground electronic state were extrapolated to the complete basis set limit. The planar trans and cis conformations were the most stable configurations for all five electronic states under study. We found that the allowed electronic transition of the cis conformer has a transition energy that is significantly higher than that predicted in previous studies. For the excited states, the internal rotation was found to be accompanied by significant non-planar distortion of both carbonyl fragments, indicating strong coupling between these molecular motions.     

Direct observation of the dynamics of electronic excitations in molecules and small clusters

Femtosecond time-resolved photoelectron spectroscopy is applied to study relaxation paths of excited states of mass-selected negatively charged clusters. As a first example, the lifetime of an excited state of the carbon trimer anion is measured directly. In addition, the mechanism of the decay, i.e., the configurations of the participating electronic states, is determined from the photoelectron spectra. In general, this method can be used to study all kinds of electronic excitation and relaxation processes in mass-selected nanoparticles.     

A theoretical study of potential energy curves and spectroscopic constants of VC

Potential energy curves for the various low-lying electronic states of VC have been studied using complete active space multi-configuration self-consistent field (CASMCSCF) followed by first-order and multireference singles and doubles configuration interaction (FOCI, MRSDCI) calculations. The MRSDCI calculations included up to 6 million configurations. Two very low-lying electronic states are found as candidates for the ground state of VC, namely a high spin state ⁴Δ and a low-spin ²Δ state, which is favoured at higher levels. A number of low-lying excited electronic states of VC are predicted, which are yet to be observed. The low-lying electronic states of VC are found to be ionic as inferred from the dipole moments and the charge density calculations. Electron donation and the back-donation process are suggested to be operative in the V-C bond formation.     

Heating or cooling of gases with tunable laser radiation

A scheme for cooling or heating of gases using radiation from a tunable laser is proposed. Essentially the scheme consists of pumping of vibrational levels of an excited electronic state followed by reradiation to the vibrational states of a ground electronic state.     

基态和单态第一激发态的联氨单分子分解反应的密度泛函研究

本文运用密度泛函B3LYP/6-311+G(3df,2p)方法研究了联氨分子的电子结构和能量,并系统分析了联氨分子的分解反应,计算绘制了单分子联氨在基态和单态第一激发态下沿N-N分解反应的势能曲线。本文计算发现联氨分子在这两种电子态下的离解能分别是：基态58.8 kcal/mol,单态第一激发态495.5 kcal/mol。基态分子分解反应是吸热反应,而单态第一激发态分解反应是放热反应。计算发现单态第一激发态的激发能是554.2 kcal/mol。结合这两种电子态下联氨分子的红外振动频率分析,本文认为,在非强制断键的情况下,联氨分子沿N-N键均裂而生成两个NH2自由基的可能性很小。     

Electron and exciton excited states of the neutral donor in Zn Te

We have determined experimentally the electronic structure of the neutral donor in Zn Te. We see 5 different excited states which correspond to a bound exciton. Recombination of these excitons can leave the donor in an electronic excited state up to the n = 4 state. The structure seen in the n = 2 is discussed in term of configuration interaction.     

基态和单态第一激发态的联氨单分子分解反应的密度泛函研究

本文运用密度泛函B3LYP/6-311+G(3df,2p)方法研究了联氨分子的电子结构和能量,并系统分析了联氨分子的分解反应,计算绘制了单分子联氨在基态和单态第一激发态下沿N-N分解反应的势能曲线。本文计算发现联氨分子在这两种电子态下的离解能分别是：基态58.8 kcal/mol,单态第一激发态495.5 kcal/mol。基态分子分解反应是吸热反应,而单态第一激发态分解反应是放热反应。计算发现单态第一激发态的激发能是554.2 kcal/mol。结合这两种电子态下联氨分子的红外振动频率分析,本文认为,在非强制断键的情况下,联氨分子沿N-N键均裂而生成两个NH2自由基的可能性很小。     

A Spectroscopic Model for the Study of Preferential in the Ground and Excited Electronic States.

The preferential solvation of a solute molecule in mixed solvents is analysed in terms of the spectral solvent shifts. A spectroscopic model is developed in order to know the preferential solvation degree in the ground electronic state as well as in the first excited electronic state by measuring the absorption and fluorescence spectra respec tively.

Triphenylene was found to be a good model probe molecule in n-butanol/carbon tetrachloride mixtures for both electronic states. Furthermore Tryphenylene in its ground electronic state was studied in chloroform/methanol mixtures.     

What is so mysterious about the electronic states of SCI?

The 15 lowest lying doublet electronic states of the molecule SCI have been investigated theoretically at a high level of correlation treatment (MRCI). For the ground state (X ²II), spectroscopic constants were obtained from a set of eight vibrational intervals. This result extends our knowledge about this state beyond the experimentally known data that presently were derived from only two bands. Spin-orbit constants, transition probabilities and radiative lifetimes complement its spectroscopic characterization. For the excited electronic states, a global view of the doublet states is presented that can help us understand the scarcity of experimental data on electronic transitions for this system and also the difficulty of assigning the only two transitions so far recorded. Most of these states are repulsive, and for the few high lying bound ones, of Rydberg character, avoided crossings restrict the number of accessible vibrational states. Crossing by repulsive states and predissociation is also a factor that can prevent further emissions. Two new bound excited states, ²δ and ²Σ, predicted in this study, are of direct relevance to an interpretation of the limited experimental data available on electronic transitions.     

Energy levels of the Fröhlich polaron in a spherical quantum dot

The one-phonon variational state is suitably applied to describe the ground state and excited states of the Fröhlich polaron bound to a quantum dot. A general analytical expression for the electronic energy spectra and the polaron binding energy for different electronic subband bound states in a quantum dot is presented and discussed with reference to the parameters of a real solid.