Chemically Produced Excited States

Electronically excited states of organic molecules are formed in many chemical reactions. Such chemically produced excited states are (with one exception) identical to light produced excited states, and they undergo the molecular transformations expected of such states (“photochemistry without light”). The excited states can also be used in energy transfer experiments. This review covers the generation of chemically produced excited states, the chemical reactions they undergo, and the possible role of chemically produced excited states in biology.     

The operations of quantum logic gates with pure and mixed initial states

The implementations of quantum logic gates realized by the rovibrational states of a C(12)O(16) molecule in the X((1)Σ(+)) electronic ground state are investigated. Optimal laser fields are obtained by using the modified multitarget optimal theory (MTOCT) which combines the maxima of the cost functional and the fidelity for state and quantum process. The projection operator technique together with modified MTOCT is used to get optimal laser fields. If initial states of the quantum gate are pure states, states at target time approach well to ideal target states. However, if the initial states are mixed states, the target states do not approach well to ideal ones. The process fidelity is introduced to investigate the reliability of the quantum gate operation driven by the optimal laser field. We found that the quantum gates operate reliably whether the initial states are pure or mixed.     

Ground and valence-excited states of SF: a multireference configuration interaction with single and double excitations+Q study

Ab initio calculations on the ground and valence-excited states of the sulfur monofluoride radical have been performed using entirely uncontracted all-electron augmented correlation consistent polarized valence quintuple zeta basis sets and the internally contracted multireference configuration interaction with single and double excitations method and Davidson correction (+Q). Potential-energy curves of all valence electronic states and the spectroscopic constants of several bound states are fitted. It is the first time that the entire 27-omega states generated from the 12 valence lambda-S states which come from the S(3P(g)) and F(2P(u)) atomic states of SF radical have been studied theoretically. The effects of spin-orbit coupling and the avoided crossing rule between omega states of the same symmetry are analyzed. The calculated results reproduce well the available experimental values and predict the properties of several bound excited states that have never been observed in experiment. The transition properties of the dipole-allowed transitions from bound excited states to the ground state are predicted for the first time, including the transition dipole moments, the Franck-Condon factors, and the radiative lifetimes.     

Probing Rapidly‐Ionizing Super‐Atom Molecular Orbitals in C60: A Computational and Femtosecond Photoelectron Spectroscopy Study

Super‐atom molecular orbitals (SAMOs) are diffuse hydrogen‐like orbitals defined by the shallow potential at the centre of hollow molecules such as fullerenes. The SAMO excited states differ from the Rydberg states by the significant electronic density present inside the carbon cage. We provide a detailed computational study of SAMO and Rydberg states and an experimental characterization of SAMO excited electronic states for gas‐phase C₆₀ molecules by photoelectron spectroscopy. A large band of 500 excited states was computed using time‐dependent density functional theory. We show that due to their diffuse character, the photoionization widths of the SAMO and Rydberg states are orders of magnitude larger than those of the isoenergetic non‐SAMO excited states. Moreover, in the range of kinetic energies experimentally measured, only the SAMO states photoionize significantly on the timescale of the femtosecond laser experiments. Single photon ionization of the SAMO states dominates the photoelectron spectrum for relatively low laser intensities. The computed photoelectron spectra and photoelectron angular distributions are in good agreement with the experimental results.     

Control of wave packets in Li(2) by shaping the pump and probe pulses for a state-selected pump-probe analysis of the ionization continuum

Wave packet signals in Li(2) prepared by shaped pump pulses are also detected with state-selected shaped probe pulses in the ionization continuum. The results show that the final states are discrete Rydberg states instead of continuum states. Final autoionizing states in the continuum are observed and characterized. By selecting specific resonant rovibrational electronic transitions from the superposition states prepared in the wave packets to the final autoionizing states with the pulse shaping system, the modulation depths of the wave packet signals are increased by as much as 5.20+/-0.03 times. Control of the wave packets is also realized by shaping the probe pulses to select specific resonant transitions between the states in the wave packets and the highly excited Rydberg states. The detected amplitude ratio of one specific vibrational quantum beat to one specific rotational quantum beat can be decreased by ten times.     

Extensive ab initio study of the electronic states of SCl including spin-orbit coupling

The effect of different basis sets for calculation of the spectroscopic constants of the ground state of sulfur monochloride (SCl) was analyzed using scalar relativistic multireference configuration interaction with single and double excitations plus Davidson correction. Then the generally contracted all-electronic correlation-consistent polarized valence quintuple zeta basis sets were selected to compute the electronic states of SCl including 12 valence and 9 Rydberg lambda-S states. The spin-orbit coupling effect was calculated via the state interaction approach with the full Breit-Pauli Hamiltonian. This effect splits these lambda-S states into 42 omega states. Potential-energy curves of all these states are plotted with the help of the avoided crossing rule between the electronic states of the same symmetry. The structural properties of these states are analyzed. Spectroscopic constants of bound excited states that have never been observed in experiment are obtained. The transition dipole moments and the Franck-Condon factors of several transitions from low-lying bound excited states to the ground state were also calculated.     

Extensive ab initio study of the valence and low-lying Rydberg states of BBr including spin-orbit coupling

The electronic states of the BBr molecule, including 12 valence states and 12 low-lying Rydberg states, have been studied at the theoretical level of MR-CISD+Q with all-electron aug-cc-pVQZ basis sets and Douglas-Kroll [Ann. Phys. (N.Y.) 82, 89 (1974)] scalar relativistic correction. The spin-orbit coupling effect in the valence states was calculated by the state interaction approach with the full Breit-Pauli Hamiltonian. This is the first multireference ab initio study of the excited electronic states of BBr. Potential energy curves of all states were plotted with the help of the avoided crossing rule between electronic states of the same symmetry. The structural properties of these states were analyzed. Computational results reproduced most experimental data well. The transition properties of the a (3)Pi(0(+) ), a (3)Pi(1), and A (1)Pi(1) states to the ground state X (1)Sigma(0(+) ) (+) transitions were obtained, including the transition dipole moments, the Franck-Condon factors, and the radiative lifetimes. The evaluated radiative lifetime of the a (3)Pi(0(+) ), and a (3)Pi(1) states are near 1 ms, much longer than that of the A (1)Pi(1) state.     

本体柱状的线形嵌段共聚物在受限状态下的自组装结构

综述了使用计算机模拟方法研究在本体状态下形成柱状结构的线形二嵌段和三嵌段共聚物在平行板间和纳米圆孔内的自组装结构.研究发现,嵌段共聚物体系在受限状态下自组装可以得到与本体状态下不同的纳米结构,调整受限状态的物理化学性质可以调控受限体系的相行为,从而诱导体系形成特定的结构.模拟研究还发现不同相分离强度和链结构的体系,在相同的受限状态下表现出不同的相行为.因此在制备纳米结构材料的研究中,人们要根据嵌段共聚物体系的特定性质,选择相应的受限环境,才能够实现有效的控制.     

Two states and two more in the mechanisms of hydroxylation and epoxidation by cytochrome P450

Past studies have shown that oxidation reactions by P450 Compound I (Cpd I) can be described by two competing quartet and doublet spin states, which possess three unpaired electrons, hence tri-radicals. One electron excitation from the delta orbital to sigma* xy generates two states that possess five unpaired electrons, so-called penta-radicals, in sextet and quartet situations, and which were shown by theory to lie only approximately 12-14 kcal/mol higher in energy than the tri-radical ground states (ref 7). The present study focuses on the C-H hydroxylation and C=C epoxidation of propene by these penta-radical states. It is shown that the initial energy differences, between the penta-radical and tri-radical states, diminish along the reaction pathway, due to the favorable and cumulative exchange stabilization of the more open-shell species. Furthermore, theory suggests that hydrogen bonding to the thiolate ligand, and general polarity of the environment, reduce these gaps further, thereby making the penta-radical states accessible to ground-state reactivity. The interconversion between the tri-radical and penta-radical states along the reaction coordinate will depend on the dynamics of spin-flips and energy barriers between the states. Especially interesting should be the region of the reaction intermediates; for both epoxidation and hydroxylation, this region is typified by a dense manifold of spin states and electromeric states (that differ by the oxidation state of iron), such that the total reactivity would be expected to reflect the interplay of these states, giving rise to multistate reactivity.     

Study on the C_(60)-Caged States of H_2 and N_2

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The construction of the Gilmore–Perelomov coherent states for the Kratzer–Fues anharmonic oscillator with the use of the algebraic approach

By applying the algebraic approach and the displacement operator to the ground state, the unknown Gilmore–Perelomov coherent states for the rotating anharmonic Kratzer–Fues oscillator are constructed. In order to obtain the displacement operator the ladder operators have been applied. The deduced SU(1, 1) dynamical symmetry group associated with these operators enables us to construct this important class of the coherent states. Several important properties of these states are discussed. It is shown that the coherent states introduced are not orthogonal and form complete basis set in the Hilbert space. We have found that any vector of Hilbert space of the oscillator studied can be expressed in the coherent states basis set. It has been established that the coherent states satisfy the completeness relation. Also, we have proved that these coherent states do not possess temporal stability. The approach presented can be used to construct the coherent states for other anharmonic oscillators. The coherent states proposed can find applications in laser-matter interactions, in particular with regards to laser chemical processing, laser techniques, in micro-machinning and the patterning, coating and modification of chemical material surfaces.     

Symmetry-dependent vibrational excitation in N 1s photoionization of N2: experiment and theory

We have measured the vibrational structures of the N 1s photoelectron mainline and satellites of the gaseous N2 molecule with the resolution better than 75 meV. The gerade and ungerade symmetries of the core-ionized (mainline) states are resolved energetically, and symmetry-dependent angular distributions for the satellite emission allow us to resolve the Sigma and Pi symmetries of the shake-up (satellite) states. Symmetry-adapted cluster-expansion configuration-interaction calculations of the potential energy curves for the mainline and satellite states along with a Franck-Condon analysis well reproduce the observed vibrational excitation of the bands, illustrating that the theoretical calculations well predict the symmetry-dependent geometry relaxation effects. The energies of both mainline states and satellite states, as well as the splitting between the mainline gerade and ungerade states, are also well reproduced by the calculation: the splitting between the satellite gerade and ungerade states is calculated to be smaller than the experimental detection limit.     

H原子在Ru(1121)台阶面上的吸附位和吸附态

利用原子和表面簇合物相互作用的五参数Morse势方法(简称5-MP)研究了H-Ru(1121)台阶面吸附体系,并利用推广的LEPS方法研究了2H-Ru(1121)体系,探讨了表面吸附态之间的相互作用.研究结果表明,H原子在开放的Ru(1121)台阶面表面上的晶胞存在4种不等价的表面三重吸附态.还存在两类与表面有直接扩散通道的内层吸附态.理论分析表明,TDS实验出现的α态是与内层吸附态有强相互作用的强排斥表面吸附态,β态为弱排斥表面吸附态,而γ态为与内层吸附态无相互作用的表面吸附态.实验上将α态归属为四重吸附态的推测没有获得理论结果的支持.     

A re-interpretation of the UV-photoelectron spectra of dewar benzene,norbornadiene and barrelene by ab initio configuration interaction calculations

Ab initio configuration interaction calculations of the ground and cationic states of Dewar benzene, norbornadiene and barrelene have enabled a firm assignment of the uv-photoelectron spectra in the range 8–16 eV to be made. Many of the states are of Koopman's one-electron process type, and the order of states is close to that of the SCF double zeta ground state calculations. A number of shake-up doublet states were computed, and for barrelene at least, these appear from about 12 eV onwards; the lowest lying triplet and singlet states for barrelene were computed at 3.82 and 6.04 eV, respectively, and most of the low-lying shake-up states are related to this HOMO—LUMO pair of transitions.     

Electronic states at the silicon-silicon dioxide interface

Localized electronic states at the silicon/silicon dioxide interface are reviewed, and the current knowledge of interface states and fixed oxide charges, and how they influence the characteristics of the MOS structure, is summarized. Experimental results on the properties of these two classes of localized states are presented and discussed. General trends of properties over a very extensive amount of data are noted and an overall picture of these states is given. Various phenomenological models for these electronic states are reviewed and critically discussed. It is pointed out that the current understanding of localized states is, in general, far from satisfactory, and a complete picture is lacking. Theoretical efforts on computing the energy levels of these electronic states are summarized. Most of these approaches are based on highly simplified structures, such as a simple unit cell with an atom missing. While they have been moderately successful, more realistic approaches are still needed. Finally, some theoretical techniques are introduced, in the hope that they may have applications to these problems, and the need for more measurements of non-electrical properties of these states is emphasized.     

Dynamics of highly excited nitroaromatics

Although the photodissociation of nitroaromatics in low excitation electronic states has been extensively studied in recent decades, little is known about the highly excited electronic states. The fragmentation dynamics of three nitroaromatics, nitrobenzene, o-nitrotoluene, and m-nitrotoluene, in highly excited states, populated by the absorption of two photons at 271 nm, are studied with time-of-flight mass spectrometry. The temporal evolutions of the highly excited states are monitored by one-photon ionization at 408 nm. The transients of parent and fragment ions exhibit two ultrafast deactivation processes. The first process is ultrafast internal conversion from the initial excitation to Rydberg states in tens of femtoseconds. The second one is conversion from the Rydberg states to the vibrational manifold in the ground electronic states within hundreds of femtoseconds. The internal conversion process is accelerated by methyl substitution. In o-nitrotoluene, the two processes become much faster due to the hydrogen transfer from the CH(3) to the NO(2) group (ortho effect).     

Particles and holes in the unitary group method

Based on the definition for complementary Gel'fand states, we proved the simple relationship between the matrix elements of particle states and those of hole states by unitary calculus.