Narrow Results

A combination of density functional theory and multi-reference configuration interaction methods (DFT/MRCI) has been applied to the calculation of electronic absorption spectra in a series of porphyrin-type molecules. The calculated excitation energies and oscillator strengths for free-base porphyrin (PH₂) are in excellent agreement with experiment for both lower and higher excited states which are characterized by a significant contribution of double excitations (>20%). The 4¹B_2u, 4¹B_3u, and 5¹B_2u states are assigned to the L-band and the 7¹B_3u state to the M-band. The results for the hydroporphyrins chlorin (CH₂) and bacteriochlorin (BH₂) are in agreement with the experimentally observed increase in intensity for the Q-bands relative to PH₂. For BH₂ we predict a red shift of the Q_x-band (0.2 eV) and a blue shift of the B-band (0.5–0.7 eV) in comparison to both PH₂ and CH₂. For porphyrazine (PzH₂) and the commercial pigment phthalocyanine (PcH₂) the calculated oscillator strengths of the Q- and B-bands are of comparable size explaining the intense color of PcH₂. For the metalloporphyrins with magnesium (PMg) and zinc (PZn), the x- and y-polarized components of the Q- and B-bands collapse, due to the higher D_4h symmetry of the molecules. The calculations reproduce the slight, experimentally observed increase in the oscillator strength of the Q-band and the decrease for the B-band. These effects are ascribed to the electropositive nature of the metals relative to hydrogen. Except for the Q-bands, which are adequately described by the 'four-orbital model,' it is essential to account for excitations outside the four frontier orbitals as well as double and triple excitations for accurate reproduction of experimental data. We compare our results both with experiment and, where available, recent first-principle SAC-CI, MRMP, and TDDFT calculations.

The excited states of four hemes, c-552, c-554, c-556, and c-559, in a c-type cytochrome subunit of the photosynthetic reaction center (PSRC) of Rhodopseudomonas (Rps.) viridis were studied using the symmetry-adapted cluster (SAC)-configuration interaction (CI) method. c-552 has two imidazole ligands, while the other three hemes have imidazole and methionine ligands. The electronic states of these four hemes are affected significantly by both the ligands and protein and water environments. The ligand effect classifies the four hemes into two groups, while the environmental effect is unique in each heme. The HOMO–LUMO energy separation of c-552 is much smaller than those of the other hemes, and therefore, the low-lying excited states of c-552 are more stable than those of the other hemes. The low-lying excited states and their oscillator strengths of c-559 are significantly modified by the environment when compared with c-556 and c-554. Some observed UV peaks of the PSRC of Rps. viridis were found to have been assigned reasonably to the excited states of these four hemes in a previous report. The calculated linear dichroism angles also supported our assignment.

The properties of N = 41 isotones are investigated systemically by using the nonlinear relativistic mean field theory. It is found that all the calculating binding energies with four different interactions are comparable for the ground and low-lying excited states, and very close to the data available. The calculations show that there exists a neutron halo in the first excited state in ⁶⁹Ni, as well as in the second excited state in ⁶⁹Ni. It is also predicted that there exists a neutron halo in the first excited state in ⁶⁵Cr, ⁶⁶Mn, ⁶⁷Fe and ⁶⁸Co.

The mass spectrum of spin-1/2 baryons in both parity channels is computed using the methods of lattice QCD in the quenched approximation. An anisotropic action with anisotropy a_s/a_t = 3 is employed, using tree-level coefficients with tadpole improvement. Clear splittings from the nucleon ground state are observed with smeared operators and 500 configurations. Methods for extracting the first excited states are investigated. Using the quark mass dependence of the masses, qualitative comparisons are made with previous calculations and experiment.

In this paper, we first derive two QCD sum rules QCDSR I and QCDSR II which are, respectively, used to extract observable quantities of the ground states and the first radially excited states of the D-wave vector $\rho$ and $\varphi$ mesons. In our calculations, we consider the contributions of vacuum condensates up to dimension-7 in the operator product expansion. The predicted masses for $1^3{D}_1$$\rho$ meson and $2^3{D}_1$$\varphi$ meson are consistent well with the experimental data of $\rho$($1700$) and $\varphi$($2170$), respectively. Besides, our analysis indicates that it is reliable to assign the recent reported $Y$($2040$) state as the $2^3{D}_1$$\rho$ meson. Finally, we obtain the decay constants of these states with QCDSR I and QCDSR II. These predictions are helpful not only to reveal the structure of the newly observed $Y$($2040$) state, but also to establish $\varphi$ meson and $\rho$ meson families.

The effect of laser on the nonparabolicity of the conduction band for hydrogenic donor states like 1s, 2s, 2p_± and 2p₀ in a GaAs/Al_xGa_1-xAs quantum well have been computed in a finite barrier model using variational principle in the effective mass approximation. The limiting values of the ground state and few excited state binding energies for a laser dressed-donor have been obtained. The results are presented and discussed.

Measurements of emission cross sections for the ${\mathrm{\text{O}}}^{+}-{\mathrm{\text{N}}}_2$ collision system with the incident beam of 1–10 keV ${\mathrm{\text{O}}}^{+}$ in the ground ${\mathrm{\text{O}}}^{+}{(}^{4}S$) and metastable ${\mathrm{\text{O}}}^{+}{(}^{2}D)$ and ${\mathrm{\text{O}}}^{+}{(}^{2}P)$ states are reported. The emission cross section induced by incident ions in the metastable state ${\mathrm{\text{O}}}^{+}{(}^{2}P)$ is much larger than that for the ground ${\mathrm{\text{O}}}^{+}{(}^{4}S)$ state. The emission cross section of ${\mathrm{\text{N}}}_2^{+}$ ion for $(0,0)$, $(0,1)$, and $(1,2)$ bands system is measured and the ratio of intensities for these bands is established as $10:3:1.$ It is shown that the cross sections for the ${\mathrm{\text{N}}}^{{+}^{\ast }}$ ions emissions in the dissociative charge exchange processes increase with the increase of the incident ion energy. The energy dependence of the emission cross section of the band $(0,0)$$\lambda =391.4$ nm of the first-negative band system of the ${\mathrm{\text{N}}}_2^{+}$ and degree of linear polarization of emission in ${\mathrm{\text{O}}}^{+}-{\mathrm{\text{N}}}_2$ collision are measured for the first time. An influence of an admixture of the ion metastable state on a degree of linear polarization is revealed. The mechanism of the processes realized during collisions of ground and metastable oxygen ions on molecular nitrogen have been established. It is demonstrated that for ${\mathrm{\text{O}}}^{+}-{\mathrm{\text{N}}}_2$ collision system the degree of linear polarization by metastable ${\mathrm{\text{O}}}^{+}{(}^{2}P)$ ions is less compared to those that are in the ground ${\mathrm{\text{O}}}^{+}{(}^{4}S)$ state and the sign of emission of degree of linear polarization of excited molecular ions does not change.

We have investigated quantum entanglement for two interacting ultracold bosonic atoms in one-dimensional harmonic traps. The effective potential is modeled by delta interaction. For this two-atom system, we have investigated quantum entanglement properties, such as von Neumann entropy and linear entropy for its ground state and excited states. Using a computational scheme that is different from previously employed, a total of the lowest 16 states are studied. Here we show the dependencies of entanglement properties under various interacting strengths. Comparisons for the ground state entanglement are made with earlier results in the literature. New results for the other 15 excited states are reported here.

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat universe. Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). Thus direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper, we study transitions to the excited states, focusing on the first excited state at 50 keV of Iodine A=127. We find that the transition rate to this excited state is ≼10 percent of the transition to the ground state. So, in principle, the extra signature of the gamma ray following its de-excitation can be exploited experimentally.

Muonic atoms formation in excited states is investigated. Using the two-state approximation (TSA), differential cross-sections for charge-transfer reaction as a(1s)+μ^-(a = H, D, T) collisions are calculated in the energy range from 0.001 eV to 1 eV. Our results indicate that the distribution of the principal quantum number n for captured muons has a peak around n = 14. It is also shown that the dependence of the differential cross-section on l diminishes with increase of energy. The results are in agreement with other calculations.

Two 0⁺ excited states of ⁴⁰Ca have been investigated by the potential energy surface (PES) obtained from both adiabatic and diabatic constrained approaches, combined with the relativistic mean field (RMF) theory. A well-defined second minimum appears on the diabatic PES that does not exists on the adiabatic PES. The configurations of these two 0⁺ excited states are determined as 4p–4h and 8p–8h excitation from their counterparts at the spherical configuration. The excited energies were reduced by microscopic correction for the center-of-mass motion, and a gap at 18 appears in their single particle diagrams.

Excited states of ¹¹⁷Sn have been populated using the fusion-evaporation reaction ¹¹⁴Cd(⁷Li, 1p3n) at a beam energy of 48MeV. A total of nine new transitions have been identified and added into the level scheme of ¹¹⁷Sn. Based on the systematical comparisons with the neighboring Sn isotopes and the configuration-fixed constrained triaxial relativistic mean-field (RMF) calculations, a collective structure and two isomers are proposed to exist in ¹¹⁷Sn. The phenomenon of shape coexistence has been extended to A = 117 in odd-A Sn isotopes for the first time.

Based on the framework of the modified potential cluster model (MPCM), with orbital states classified using Young diagrams, we consider the possibility of prediction absentee of experimental data for the total cross-sections of the radiative neutron capture on ${}^{11}$B to the first excited state of ${}^{12}$B at 0.95314MeV (2${}^{+}$), to the second excited state of ${}^{12}$B at 1.67365MeV (2⁻), and prediction absentee of experimental data for the total cross-sections to the third and fourth excited states of ${}^{12}$B at 2.6208MeV (1⁻) and 2.723MeV (0${}^{+}$), for a reaction energy of 10meV to 7MeV. We calculate the reaction rate for a temperature range of 0.01–10.0 $T_9$ on the basis of the obtained cross-sections, which take into account resonances up to 5MeV. We then demonstrate that low-lying resonances have a significant impact on the reaction rate of capture. An approximation for the calculated reaction rate is derived based on an analytical formula.

The influence of Γ–X band crossing due to the applied hydrostatic pressure on the diamagnetic susceptibility (χ_dia) of a donor in low-lying excited states like 2s, 2p₀, 2p_± in a GaAs/Al_xGa_1-xAs Quantum Well has been investigated in the effective mass approximation by considering the nonparabolicity of the conduction band. We notice that the effect of Γ–X band mixing is significant on χ_dia of a donor lying in excited states. Moreover, the effect of non-parabolicity on χ_dia is also predominant for lower well width region. The results are presented and discussed.

New global ab initio potential energy surfaces (PES) are presented for the low-lying 1¹A′, 1¹A′′ and 2¹A′ electronic states which are correlated to O(¹D) + HCl. These potential energy surfaces are computed by using the multi-reference configuration interaction method with the Davidson correction (MRCI+Q). The reference functions are constructed by the complete active space self-consistent field (CASSCF) calculations using the quadruple zeta + polarization basis set augmented with diffuse functions. The computations are carried out at about 5000 molecular conformations on each three-dimensional potential energy surface. The high accuracy of the computations is confirmed by a comparison with the available most accurate data for the ground state 1¹A′; thus the present work is the first report of the accurate potential energy surfaces for the two excited states. Three low-lying transition states on the excited surfaces, two (TS2 and TS4) on 1¹A′′ and one (TS3) on 2¹A′, are found. Since TS2 and TS3 are as low as 0.07 eV and 0.28 eV, respectively, and correlate to the OH(²Π) + Cl(²P) product, these excited surfaces are expected to play quite important roles in the reaction dynamics. Possible effects of nonadiabatic couplings among the three PESs are also briefy discussed, although the nonadiabatic couplings have not yet been estimated. The quantum reaction dynamics on these three PESs are discussed in the second accompanying paper, Paper II.

Using the accurate global potential energy surfaces for the 1¹A′, 1¹A′′, and 2¹A′ states reported in the previous sister Paper I, detailed quantum dynamics calculations are performed for these three adiabatic surfaces separately for J = 0 (J: total angular momentum quantum number). Overall reaction probabilities for O + HCl → OH + Cl and H + ClO, the branching ratio between the two reactions, effects of the initial rovibrational excitation, and product rovibrational distributions are evaluated in the total energy region E_tot ≤ 0.9 eV. Significant contributions to the overall reaction dynamics are found from the two excited 1¹A′′ and 2¹A′ potential energy surfaces, clearly indicating the insufficiency of the dynamics only on the ground 1¹A′ surface. The detailed dynamics on the excited surfaces are reported in the third paper of this series.

Using the accurate global potential energy surfaces for the 1¹A′′ and 2¹A′ states reported in the previous sister Paper I, detailed quantum dynamics calculations are performed for these adiabatic surfaces separately for J = 0 (J: total angular momentum quantum number). In addition to the significant overall contributions of these states to the title reactions reported in the second Paper II of this series, quantum dynamics on these excited potential energy surfaces (PES) are clarified in terms of the PES topographies, which are quite different from that of the ground PES. The reaction mechanisms are found to be strongly selective and nicely explained as vibrationally nonadiabatic transitions in the vicinity of potential ridge.

Extensions of traditional molecular dynamics to excited electronic states and non-Born–Oppenheimer dynamics are reviewed focusing on applicability to chemical reactions of large molecules, possibly in condensed phases. The latter imposes restrictions on both the level of accuracy of the underlying electronic structure theory and the treatment of nonadiabaticity. This review, therefore, exclusively deals with ab initio "on the fly" molecular dynamics methods. For the same reason, mainly mixed quantum-classical approaches to nonadiabatic dynamics are considered.

We have implemented the Coupled-Cluster Equation of Motion (CC-EOM) with single and double excitations coupled with semiempirical parameterizations, Pariser–Parr–Pople model and INDO Hamiltonians, to investigate the optical and nonlinear optical properties, electronic structures and the excited states properties for the conjugated polymers. The semiempirical parameters allow us to study the conjugated systems with extensive sizes. Firstly, by comparing with the quasi-exact Density Matrix Renormalization Group theory for the 1D conjugated chain, we find that the CC-EOM approach can give satisfactory results for both the ground state and the excited states energies. We demonstrate that our approach can be adopted to evaluate linear and nonlinear response. We find that both the real and imaginary parts of the third-order polarizability can be solved either for static and dynamic responses. Then we apply the CC-EOM approach to study the optical signatures for the polarons in conjugated polymers. We have established a solid relationship between the rigidity of a polymer and its optical signature of the polarons.

Thioanalogues of nucleic-acid bases have been shown to be the place of preferential charge or energy localization when incorporated in the system of respective regular bases. Most evidence of such behavior is based on experiments using γ-ray or other ionizing radiation. Here time dependent density functional theory (TDDFT) has been applied to investigate singlet and triplet excited state spectra of thioanalogues and some oxo-derivatives of nucleic-acid bases and compare the spectra to the calculated spectra of the regular bases as well as to the existing experimental data. It has been shown that thioanalogues have lower excitation singlet and triplet energies than are the respective energies in the regular bases. Energy localization on thioanalogues and their spectroscopic properties are related to the effect of sulfur substitution in such systems.