Radiationless decay in exciplexes with variable charge transfer

Rate constants for radiative decay, radiationless decay, and intersystem crossing are reported for a series of excited states formed by reaction of cyanoanthracene acceptors with alkylbenzenes as donors in several solvents of moderate to low polarity. The excited states have widely varying degrees of charge transfer, from essentially pure electron transfer states to pure locally excited states. The data illustrate the fundamental factors that control the contrasting relative efficiencies of radiative and radiationless processes in electron transfer compared to locally excited states. The radiationless decay rate constants can be described quantitatively as a function of the extent of charge transfer using weighted contributions from a locally excited decay mechanism and a pure electron-transfer type mechanism. The factors that control the rate constants for radiationless decay in excited states with intermediate charge-transfer character are discussed.     

Representing and selecting vibrational angular momentum states for quasiclassical trajectory chemical dynamics simulations

Linear molecules with degenerate bending modes have states, which may be represented by the quantum numbers N and L. The former gives the total energy for these modes and the latter identifies their vibrational angular momentum jz. In this work, the classical mechanical analog of the N,L-quantum states is reviewed, and an algorithm is presented for selecting initial conditions for these states in quasiclassical trajectory chemical dynamics simulations. The algorithm is illustrated by choosing initial conditions for the N = 3 and L = 3 and 1 states of CO2. Applications of this algorithm are considered for initial conditions without and with zero-point energy (zpe) included in the vibrational angular momentum states and the C-O stretching modes. The O-atom motions in the x,y-plane are determined for these states from classical trajectories in Cartesian coordinates and are compared with the motion predicted by the normal-mode model. They are only in agreement for the N = L = 3 state without vibrational angular momentum zpe. For the remaining states, the Cartesian O-atom motions are considerably different from the elliptical motion predicted by the normal-mode model. This arises from bend-stretch coupling, including centrifugal distortion, in the Cartesian trajectories, which results in tubular instead of elliptical motion. Including zpe in the C-O stretch modes introduces considerable complexity into the O-atom motions for the vibrational angular momentum states. The short-time O-atom motions for these trajectories are highly irregular and do not appear to have any identifiable characteristics. However, the O-atom motions for trajectories integrated for substantially longer period of times acquire unique properties. With C-O stretch zpe included, the long-time O-atom motion becomes tubular for trajectories integrated to approximately 14 ps for the L = 3 states and to approximately 44 ps for the L = 1 states.     

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.     

Theory of lone pairs. IV. Molecular ion hole states of ten-electron hydrides. Molecular ionization potentials and proton affinities by direct SCF calculations

Closed-shell SCF calculations on the ground states and direct SCF calculations on the ionized doublet states were carried out for a series of ten-electron hydrides. The correlation of ionization potentials with the degree of protonation and the nuclear charge has been studied for hole states derived from excitation out of both the core and valence molecular orbitals. Calculated proton affinities of the ground states and hole states derived from a given symmetry orbital show a similar trend to that of the ionization potentials.     

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.     

Multireference configuration interaction studies on the ground and excited states of N2O2: the potential energy curves of N2O2 along N-N distance

In this paper, the ground and excited states of N2O2 were studied at the multireference configuration interaction (MRCI) level of theory with Dunning's [J. Chem. Phys. 90, 1007 (1985); 96, 6796 (1992)] correlation consistent basis sets augo-cc-pVDZ and aug-cc-pVTZ. The geometry optimizations were performed for the ground state of N2O2. The vertical excitation energies and transition moments were calculated for the low-lying singlet states of N2O2 including the lowest three 1A1 states, two 1B1 states, one 1B2 state, and two 1A2 states at the MRCI level of theory with Dunning's correlation consistent basis sets aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ. Furthermore, for the first time, the potential energy curves were calculated at the complete active space self-consistent-field and MRCI levels of theory for as many as 12 N2O2 singlet electronic states along the N-N distance. The dissociation asymptotes of these 12 N2O2 singlet electronic states were discussed.     

Transition intensities and fluorescence lifetimes for regular and chaotic states of LiCN

Transition intensities for the excitation of ground state LiCN to many vibrational levels, including ones previously predicted to be chaotic, are calculated. This direct excitation is found to be efficient for stretching excitations but unlikely to be useful for populating chaotic states as they require significant bending excitation. The fluorescence lifetimes for these vibrationally excited states are computed and show a remarkable structure. The regular states all lie in progressions labelled by a single stretching quantum number while the lifetimes of chaotic levels show no structure. Fluorescence spectra are found to be sharp for regular and diffuse for chaotic states. It is thus suggested that fluorescence properties could provide a useful experimental probe in the search for chaotic vibrational states.     

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.     

Stepwise laser photolysis studies of beta-bond cleavage in highly excited triplet states of biphenyl derivatives having C-O bonds

Photochemical profiles of beta-bond dissociation in highly excited triplet states (Tn) of biphenyl derivatives having C-O bonds were investigated in solution, using stepwise laser photolysis techniques. The lowest triplet states (T1) were produced by triplet sensitization of acetone (Ac) upon 308-nm laser photolysis. The molar absorption coefficients of the T1 states were determined using triplet sensitization techniques. Any photochemical reactions were absent in the T1 states. Upon 355-nm laser flash photolysis of the T1 states, they underwent fragmentation, because of homolysis of the C-O bond in the Tn states from the observations of the transient absorption of the corresponding radicals. The quantum yields (Phidec) for the decomposition of the T1 states upon the second 355-nm laser excitation were determined. Based on the Phidec values and the bond dissociation energies (BDEs) for the C-O bond fission, the state energies (ERT) of the reactive highly excited triplet states (TR) were determined. It was revealed that (i) the Phidec was related to the energy difference (DeltaE) between the BDE and the ERT, and (ii) the rate (kdis) of beta-cleavage in the TR state was formulated as being simply proportional to DeltaE. The reaction mechanism for beta-bond cleavage in the TR states was discussed.     

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.     

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.     

Natural states of interacting systems and their use for the calculation of intermolecular forces.: I. General theory of the natural states of interacting systems

The theory of the primitive function of a supersystem consisting of interacting subsystems is concisely reviewed and the subsystem density matrices and the natural states of the interacting subsystems are defined. Integro-differential equations for the natural states are derived and the physical meaning of these states - which differ basically from spectroscopic states - is discussed.     

Non-Born-Oppenheimer variational calculation of the ground-state vibrational spectrum of LiH+

Very accurate, rigorous, variational, non-Born-Oppenheimer (non-BO) calculations have been performed for the fully symmetric, bound states of the LiH(+) ion. These states correspond to the ground and excited vibrational states of LiH(+) in the ground (2)Sigma(+) electronic state. The non-BO wave functions of the states have been expanded in terms of spherical N-particle explicitly correlated Gaussian functions multiplied by even powers of the internuclear distance and 5600 Gaussians were used for each state. The calculations that, to our knowledge, are the most accurate ever performed for a diatomic system with three electrons have yielded six bound states. Average interparticle distances and nucleus-nucleus correlation function plots are presented.     

He2+和He2++分子离子基态和激发态的特性研究

采用SAC/SAC-CI方法在CC-PV5Z基组下, 计算研究了He2+、He2++的基态及低激发态的分子特性, 给出了其基态和一些激发态的势能函数和光谱数据(Be、αe、ωe和ωeχe). 从群论出发推导了相应状态的离解极限；与已有实验结果的He2+(X2Σu+)相比, 计算结果令人满意. 还计算了激发态2Πu、4Σu+和4Πg的结构与光谱数据. 对于He2++, 计算的九个电子态中只有三个态(X1Σg+、1Σg+和1Σu+)属束缚态, 并得到了其光谱常数. 用价键理论模型的不相交规则对He2++基态的势能曲线极大点产生的原因做了较好的分析.     

Electronic Structure and Catalysis on （001） Polar Surface of Cubic Zirconia

The electronic structure of (001) polar surface of cubic zirconia was studied by GGA(WC) approximation. We found the cubic lattice near (001) surface showed an intensive tendency to transfer to tetragonal lattice. The metallic state appeared on both the terminations. For O-termination, some O2p states were vacated and hole carriers concentrated on surface oxygen-ions. For Zr-ermination, some Zr4d states became partial occupied for the loss of O2p states. We observed the hole states were mainly localized at the corresponding ions on surface for both the terminations, while the charge states on Zr-termination were dispersed on surface.     

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.     

The Role of Surface States in the Oxygen Evolution Reaction on Hematite

Hematite (α‐Fe₂O₃) is an extensively investigated semiconductor for photoelectrochemical (PEC) water splitting. The nature and role of surface states on the oxygen evolution reaction (OER) remain however elusive. First‐principles calculations were used to investigate surface states on hematite under photoelectrochemical conditions. The density of states for two relevant hematite terminations was calculated, and in both cases the presence and the role of surface states was rationalized. Calculations also predicted a Nerstian dependence on the OER onset potential on pH, which was to a very good extent confirmed by PEC measurements on hematite model photoanodes. Impedance spectroscopy characterization confirmed that the OER takes place via the same surface states irrespective of pH. These results provide a framework for a deeper understanding of the OER when it takes place via surface states.     

Theoretical investigation of the ground and low-lying excited states of nickel carbide, NiC

The electronic structure and bonding of 19 states of the diatomic nickel carbide (NiC) has been studied by multireference methods. Potential energy curves have been constructed for all states, whereas for the three lowest states of symmetries X (1)Sigma(+), a (3)Pi, and A (1)Pi well separated from the rest of the states, special attention was paid through the use of very large basis sets and the calculation of core-valence correlation and scalar relativistic effects. The recommended binding energies for these states are 91, 67, and 54 kcal/mol with respect to the ground state atoms. Our results in general can be considered in fair agreement with the limited experimental findings.