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Abstract: The primary exciton dynamics of colloidal indirect bandgap AlP nanocrystals are characterized with ultrafast transient absorption spectroscopy. A 400-nm excitation results in a high yield formation of an emissive exciton with a ∼1-ns lifetime and a 50-nm bandwidth red-shifted emission. Multi-wavelength target analysis is used to decompose the measured signals into sequential and parallel models, which interpret the measured data as an emissive exciton with a 1.2-ns decay time and a dark exciton which is attributed to surface trapping. Reconstructed nonlinear absorption spectra resolve a broad optical gain persisting for >1ns. The 15% emission yield demonstrates that colloidal AlP nanocrystals are useful as a potential broadband, high efficiency optoelectronics material. [Copyright &y& Elsevier]

Abstract: Absorption and emission spectra of supramolecular complexes (SC) placed in the proximity of a metal nanoparticle (MNP) are computed using a microscopic model. Concerning the absorption of a J-aggregate type SC the treatment predicts a remarkable rearrangement of Frenkel-exciton oscillator strength where all exciton levels become visible. Time and frequency resolved emission spectra display a SC–MNP coupling dependent line-shift, directly reflecting the MNP-induced electron-vibrational level renormalization. [Copyright &y& Elsevier]

Abstract: A theoretical analysis of molecular excitons in crystalline p-Nitro-Aniline (PNA) is presented. The approach is general and can be straightforwardly extended to the calculation of the exciton structure of other molecular crystals or aggregates. Based on the evaluation of transition density matrices (TDM), the method allows to easily classify the excited states of interacting molecules on the basis of those of the constituent molecules. Exciton couplings of selected dimers within the PNA crystal have been evaluated and the exciton dispersion has been determined. The experimental absorption spectrum of PNA powders can be analysed in details based on the exciton density of states. [ABSTRACT FROM AUTHOR]

Abstract: The dimol absorption of O2 at 630nm was performed to generate O2 a1Δg in the gas phase. The pure collision-induced phosphorescence spectrum was recorded around 1260nm at the O2 pressure of 130atm. The excitation spectrum, recorded by measuring the near-IR emission intensity, had the same spectral shape as that of the dimol absorption spectrum in 620–640nm. The quadratic pressure dependence of the phosphorescence intensity evidenced that the emission was induced by collision. The self-quenching rate constant of O2 a1Δg has been estimated to be (1.7±0.2)×10−18 cm3 molecule−1 s−1. [Copyright &y& Elsevier]

Abstract: The temperature dependence of the position of the so-called anomalous band peaked at in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results. [Copyright &y& Elsevier]

Abstract: The structures of heterobinuclear complex, [AuIPtII(CN)2(PH2CH2PH2)2]+ (2), in the ground and lowest-energy triplet excited states were optimized by the MP2 and unrestricted MP2 methods, respectively. The metal-localized transition shortens the Au–Pt distance about 0.321Å in the excited state with respect to 2.912Å one in the ground state. This is further evident in the calculated stretching frequencies and bond orders of Au–Pt. The experimental absorption spectra are well reproduced by the time-dependent density functional theory (TD-DFT) calculations. The present investigation was compared with the previous results of the homobinuclear (1) and (3). [Copyright &y& Elsevier]

Abstract: The title cobalt(III) complexes have been investigated by polarized absorption and Raman spectroscopies of the single crystals. The symmetry properties of the d-electron orbitals and of the vibrational modes attributable to the Raman bands of trans(Cl2)-[CoCl2(NH3) n (H2O)4−n ]Cl complexes (n =2,3, or 4) were examined to elucidated the peculiar observation that ligand substitution causes no splitting of the 15200-cm−1 absorption band and the 250-cm−1 Raman band. Effects of replacing the NH3 ligand with H2O on the electronic structure, atom–atom force constants and vibrational modes of these complex ions are briefly described. [Copyright &y& Elsevier]

Abstract: The spectrophotometric evaluation of NAD(P) dehydrogenase enzymatic activity is very popular as the reduced form (NAD(P)H) absorbs at 340nm, while the aromatic oxidised form does not. In this joint theoretical and experimental investigation, we identify the chromophoric unit of both the NAD(P)+ and NAD(P)H forms. Rather than a modification of size or shape of the frontier orbitals, the sharp variation in the absorption upon reduction is mainly related to the stabilisation of the occupied orbitals due to the positive charge. In addition, TD-DFT nicely reproduces the experimental wavelengths. [Copyright &y& Elsevier]

Abstract: We show that, within the coherent exciton scattering (CES) approximation, both the measured exponential band-tail and the detailed shape of the J-band region of the absorption spectrum of pseudoisocyanine aggregates can be reproduced with high accuracy, using only a single free parameter. Our numerical studies confirm analytical results that the J-band width depends crucially on the monomer absorption strength in the energy region where the J-band peak occurs. [Copyright &y& Elsevier]

Abstract: We fabricated organic photovoltaic cells by using hexadecafluorophthalocyaninatocopper (F16CuPc) as electron acceptor material and para-sexiphenyl (p-6P) as electron donor material. F16CuPc has wide absorption spectrum from 550nm to 850nm, which covers the maximum of solar photo flux. The measurement of their external quantum efficiency (EQE) demonstrated that the photocurrent comes from the excitons created in F16CuPc, which were separated into free electrons and holes at heterojunction interface of p-6P and F16CuPc. Moreover, F16CuPc with excellent air-stability improved the environmental stability of photovoltaic cells, and the unencapsulated cells exhibited the shelf lifetime of exceeding a week. [Copyright &y& Elsevier]

Abstract: Density and time-dependent density functional theory have been used to simulate the vibronic structure of the emission and absorption spectra of a typical trimethine cyanine dye. This approach combines the BH and HLYP exchange-correlation functional with the Doktorov scheme to evaluate the Franck–Condon factors. The absorption and emission spectra present a dominant band and a shoulder, which nicely reproduce the experimental data. The theoretical calculations demonstrate that the simplicity of the shape results from rather small geometry relaxations in the first excited state, though many vibrational normal modes contribute to it. [Copyright &y& Elsevier]

Abstract: The performance of ab initio calculations for the ground and excited states of the Pt(saloph) complex is examined in detail. The S0–S i and T1–T i absorption spectra are calculated, and the transition between the ground S0 state and the excited S1 state involves the HOMO-2, HOMO-1, HOMO and LUMO. Moreover, calculations show that the emissive singlet is of mixed MLCT/LLCT characteristic. On the other hand, the molecular geometry of the complex is nearly planar in the ground state while the geometry is obviously nonplanar in the excited state of S1(π, π∗) in the gas phase. [Copyright &y& Elsevier]

Abstract: ZnS nanoparticles of diameters of 3–4nm were self-assembled to form dense nanospheres of sizes ∼100nm by a colloidal precipitation method using PVP as the stabilizing agent. Studies indicated that the ZnS nanoparticles maintained their individual properties inside the nanospheres. Optical absorption spectra of the samples demonstrated the effect of quantum confinement in the ZnS nanocrystals. Room temperature photoluminescence measurements showed a sharp UV emission at ∼370nm, attributed to sulfur vacancies. [Copyright &y& Elsevier]

Abstract: The lowest excited triplet (T1) state of tri-tert-butylpyridinotribenzotetraazaporphinatozinc (ZnPcPy) has been investigated using transient absorption and phosphorescence measurements. The excited-state absorption spectrum of the self-assembled dimer ((ZnPcPy)2) exhibits two sharp absorption bands (658 and 694nm) in the Q band region, in addition to triplet-triplet absorption at 500nm. This is the first observation of the Q band of the T1 phthalocyanine dimer. [Copyright &y& Elsevier]

Abstract: Using wavefunction and density-based ab initio approaches, we have evaluated the structural parameters and the electronic absorption spectra of three para disubstituted trans azobenzene derivatives: 4,4′-Cl, 4,4′-NO2, and 4,4′-NMe2. These calculations were performed in both gas-phase and ethanol, and large basis set effects have been unravelled at the second-order Møller–Plesset level. All three derivatives are found to present a planar azobenzene core. [Copyright &y& Elsevier]

Abstract: Absorption spectra of molecular dimers are calculated within the reflection approximation which ignores the kinetic energy operators in the respective Hamiltonians. In treating a single vibrational degree-of-freedom for each monomer unit, it is found that band positions and band shapes are excellently reproduced as compared to the numerically exact calculation. In particular, it is shown that the spectra originating from the coupled electronically excited states can be related to the probability density of the initial wave function in the ground electronic state along a single center-of-mass coordinate. [Copyright &y& Elsevier]

Abstract: First-principles calculations of the phonon modes of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate in the terahertz region were performed using periodic density functional calculations. The calculated far-infrared (FIR) spectrum estimated from the phonon modes of the crystal did not correspond to the sum of the calculated spectra of the constituent cation and anion. The intramolecular modes of the methyl and sulfone group torsions and of π-bridge bends were confirmed, including in-plane and out-of-plane intramolecular bending, with the intermolecular modes contributing to the FIR absorption of the collective peaks. The assignment of FIR-active modes provides fruitful ideas for the design and synthesis of promising derivatives. [Copyright &y& Elsevier]

Abstract: The CRDS technique has been used to record CaBr and CaI absorption spectra at temperatures (about 350K) much lower than the spectra observed previously with the traditional techniques (T =1300–2000K). For the CaBr A2Π–X2Σ+ transition, the bandhead intensity distributions of the CRD and LIF spectra are similar. In contrast, one observes a significant intensity weakening of the C2Π3/2–X2Σ+ heads in the LIF spectrum of CaI. This is further manifestation of a spin–orbit selective pre-dissociation of the Ω =3/2 component of the C2Π state, confirming the recent observation of its anomalously short lifetime. [Copyright &y& Elsevier]

Abstract: We found a linear correlation between the theoretically predicted shifts and experimentally observed absorption spectra for various mutants of photoactive yellow protein, a photosensory receptor. Excitation energies of mutants were evaluated by the combination of the high level ab initio calculation for the chromophore inside and the low level ab initio calculation for the surrounding protein environment. Importantly, the electronic states of these two regions were treated both as variables and they are solved consistently to each other. The protein–chromophore interaction has been accurately reproduced by this method. [Copyright &y& Elsevier]

Abstract: Despite spin Hamiltonian parameters measured at T=77K for elongated centres in Ag2+ doped KCl and NaCl are nearly identical the transition temperature, T t, for observing an isotropic EPR spectrum is however quite different. This puzzling situation is solved through CASPT2 calculations which lead to the same value of the equatorial Ag2+–Cl− distance in both systems but to a 15pm difference between axial distances. This fact implies a strong reduction of the barrier among equivalent minima and T t on going from KCl to NaCl. The optical absorption spectrum of KCl:Ag2+ is also explained through present calculations. [Copyright &y& Elsevier]

Abstract: We investigated vibrational population relaxation for the anti-symmetric stretching mode of the thiocyanate ion (SCN−) in various polar solvents by ultrafast infrared spectroscopy. In aprotic solvents, vibrational population relaxation of SCN− takes place about 2–2.5 times more slowly than in protic solvents. We found that the vibrational relaxation rates and linewidths of the absorption spectra in protic solvents were larger than those in aprotic solvents. We discuss possible mechanisms of vibrational population relaxation and the relationship between relaxation rate and linewidth. [Copyright &y& Elsevier]

Abstract: The transient absorption spectra of N3 dye in the near-IR wavelength range were studied. To clarify the origin of the absorption peaks, the dependence of the spectra on the pH of solutions and on ligand substitution was examined, and the peak position was found to be sensitive to the aggregation state. [Copyright &y& Elsevier]

Abstract: We investigate the resonant character of the laser desorption of polycyclic aromatic hydrocarbons (PAH) in the 3.3μm range by exciting the C–H stretching with a tunable pulsed LiNbO3 optical parametric oscillator. A perfect match is obtained between the desorption yield and the optical absorption spectra of naphthalene, acenaphtene, and phenanthrene. The plume dynamics is probed by varying the delay between the desorption and ionization laser pulses. Simple calculations using Beer–Lambert and Hertz–Knudsen equations account for the absence of phase explosion mechanism and for the long desorption times observed. Analytical and technological openings of this resonant technique are discussed. [Copyright &y& Elsevier]

Abstract: Quantum calculations are performed for an anion water cluster representing the first hydration shell of the solvated electron in solution. The absorption spectra from the ground state, the instant excited states and the relaxed excited states are calculated including CI-SD interactions. Analytic expressions for the nonadiabatic relaxation are presented. It is shown that the 50fs dynamics recently observed after s→p excitation is best accounted for if it is identified with the internal conversion, preceded by an adiabatic relaxation within the excited p state. In addition, transient absorptions found in the infrared are qualitatively reproduced by these calculations. [Copyright &y& Elsevier]

Abstract: X-ray absorption spectra of small formic acid clusters, (HCOOH) n , n =1–4, were examined theoretically within the framework of density functional theory. For monomer, assignment of the first peak around 532eV was consistent with the experiment, whereas the second peak around 535eV was assigned to a mixture of three bands, O1s(C sp="0.25" />→σ*(OH), O1s(OH)→π*(OH), and O1s(OH)→σ*(OH) excitations. For the dimer, relative intensities of the oscillator strengths of O1s(Cce:hsp sp="0.12" />1s(OH)→σ*(OH) excitations decrease due to strong hydrogen bond formation, whereas those of O1s(Cce:hsp sp="0.12" />1s(OH)→π*(Ctions are insensitive to the dimerization. [Copyright &y& Elsevier]

Abstract: We have determined the absorption coefficients of the IR-active vibrational modes in solid dipicolinic acid (DPA) at 300K and observed, for the first time, the DPA absorption lines corresponding to vibrational overtones. Applications of obtained results to coherent Raman spectroscopy are discussed. [Copyright &y& Elsevier]

Abstract: We present a combined experimental and computational density functional theory (DFT)/time-dependent DFT study of the geometry, electronic structure and optical absorption spectrum of the solar-cell sensitizers cis-[Ru(4,4′-COO−-2,2′-bpy)2(X)2]4− (X=NCS, Cl) in water solution. The experimentally observed red-shift of the spectrum upon substitution of NCS-by Cl-is well reproduced by our theoretical model and appears to be related to stabilization of the t2g–π∗ HOMOs in the NCS− complex. The π∗ LUMOs of the Cl complex are destabilized by a smaller extent with respect to the HOMOs, due to the increased π-back bonding interactions with the bipyridine ligands. [Copyright &y& Elsevier]

Abstract: The absorption spectra and the photovoltaic effect in thin films consisting of a blend of p-type poly(3-hexylthiophene) and n-type acceptor [6,6]-phenyl C60 butyric acid methyl ester have been studied and a decrease in inter-band absorption in the wavelength range of 450–600nm is observed. This absorption quenching is attributed to the disordering of the poly(3-hexylthiophene) chains and a charge transfer between poly(3-hexylthiophene) and [6,6]-phenyl C60 butyric acid methyl ester, as evidenced by FTIR and X-ray photoelectron spectra. Finally, photovoltaic cells were fabricated utilizing the blend as the active layer and the device characteristics were studied. [Copyright &y& Elsevier]

Abstract: Electronic absorption spectra were recorded at room temperature in solutions of carotenoids having different numbers of conjugated double bonds, n =8–13, including a spheroidene derivatives, neurosporene, spheroidene, lycopene, anhydrorhodovibrin and spirilloxanthin. The vibronic states of , , (0) and (0) were clearly identified. The arrangement of the four electronic states determined by electronic absorption spectroscopy was identical to that determined by measurement of resonance Raman excitation profiles [K. Furuichi et al., Chem. Phys. Lett. 356 (2002) 547] for carotenoids in crystals. [Copyright &y& Elsevier]

Abstract: The transient difference absorption spectrum of a substituted α-linked oligothiophene 13-mer was measured by sub 5-fs pump–probe spectroscopy. This molecule is the longest oligothiophene studied under time-resolved investigation. The spectrum observed in the sub-ps range exhibited a feature of the dynamic Stokes shift. A simple numerical calculation based on the Franck–Condon (FC) overlaps induced by molecular vibration reproduced the modulation on the difference absorption spectrum. These results verify the time-dependent FC overlap in this molecule. [Copyright &y& Elsevier]

Abstract: In this Letter, we investigated the dimerization behavior of the red-absorbing oxazine derivative MR121. Thereby a new method to determine absorption spectra of pure non-fluorescent H-type dye dimers is presented. Therefore, the amino acid lysine is doubly labeled with the fluorescent dye in order to obtain an absorption spectrum mainly caused by dimers. By subtracting the fraction arising from monomeric dye, the dimer spectrum is generated. The extinction coefficient at absorption maximum (608nm) was estimated to be 86000±2000M−1 cm−1 per dye. Furthermore, the equilibrium constant K D for the dimerization reaction is determined to be 3300±300M−1. [Copyright &y& Elsevier]

Abstract: Picosecond transient absorption spectra of hypericin in solution have been recorded over the 350–850nm spectral range under excitation fluences, respectively, 3/4 and four times the saturation fluence. At low fluence only a weak sub-100ps decay component is detected, superimposed to the main nanosecond decay of the excited state. At high fluence a sub-10ps rising component, comparable to that of earlier reports, is observed. This novel observation is discussed within the context of the state-of-the-art theory of hypericin photophysics, involving intramolecular excited-state H atom transfer. A cooling process in the S1 state after biphotonic absorption is proposed as an alternative explanation. [Copyright &y& Elsevier]

Abstract: This work is a two-dimensional study of the photodissociation of a HCl molecule adsorbed on a proton ordered hexagonal ice surface. We apply the multi-configuration time-dependent Hartree method to study the dynamics of the hydrogen photofragment. The calculated absorption spectrum exhibits structures which are related to a temporary trapping of the hydrogen between the Cl atom and the ice surface. The angular distribution of the emitted hydrogen shows structures which are attributed to a surface rainbow effect. Moreover the results indicate that the photodissociation of HCl can lead to a diffusion of the hydrogen fragment into an ice cavity. [Copyright &y& Elsevier]

Abstract: In the reaction center (RC) of Photosystem II in photosynthesis, neighboring pigments are nearly equidistantly separated at 8–10 A center-to-center. This fact has let many people consider that excited states in the pigment assembly therein may be multimers covering more than four pigments. In reality, however, the excited states are dimeric on the central pair (P) of chlorophylls, while monomeric on other pigments. Such characterization was derived from their energy broadening which was obtained by fitting the absorption spectrum of RC, based on recent mutagenesis studies clarifying that P* is not lowest in RC differently from other photosystems. [Copyright &y& Elsevier]

Abstract: The action spectrum of tetracene photooxygenation was measured in air-saturated carbon tetrachloride in the wavelength range of 1220–1290 nm using a wavelength-tunable forsterite laser. The data show that the photoreaction occurs due to laser excitation of the transition in oxygen molecules. The molar absorption coefficient (ϵ1273) and the cross section of light absorption (σ1273) corresponding to the spectral maximum of this transition were calculated from the observed photoreaction rates. The obtained values ε1273=0.003 M−1 cm−1 and σ1273=10−23 cm2 (±20%) reasonably correlate with those extrapolated from the high-pressure oxygen absorption spectra. [Copyright &y& Elsevier]

Abstract: Triplet state properties including transient triplet absorption spectrum, intersystem crossing yields in solution at room temperature and phosphorescence spectra, quantum yields and lifetimes at low temperature as well as singlet oxygen yields were obtained for poly(N-vinylcarbazole) (PVK) in 2-methyl-tetrahydrofuran (2-MeTHF), cyclohexane or benzene. The results allow the determination of the energy value for the lowest lying triplet state and also show that triplet formation and deactivation is a minor route for relaxation of the lowest excited singlet state of PVK. In addition, they show the triplet state is at higher energy than reported heavy metal dopants used for electrophosphorescent devices, such that if this is used as a host it will not quench their luminescence. [Copyright &y& Elsevier]

Abstract: Thermoluminescence and additional absorption spectra were investigated to study color centers and valence changing of uranium in as-grown and irradiated U3+:CaF2 crystals. Glow curve of the former has only peak, while the latter has two. The trap parameters associated with individual peaks were estimated by both peak profile and curve fitting methods. A model was established to explain the U4+ reduction mechanism. Based on the model, two kinds of complexes of were tentatively supposed to be present in the as-grown U3+:CaF2. All the processes during fast heating and γ-irradiation were also illuminated. [Copyright &y& Elsevier]

Abstract: The optical absorption spectrum of the Ti8C12 and V8C12 Met-Cars is calculated using time-dependent density functional theory within a real-space, real-time scheme. Other ground-state quantities are also calculated, such as the ionization potential and the electronic affinity. The broad absorption features of the calculated absorption spectrum are related to experimental results about delayed ionization and delayed ion emission phenomena that have been observed in these structures. [Copyright &y& Elsevier]

Abstract: UV absorption spectra of benzene have been measured over the wide range of temperature and pressure from the ambient state to the supercritical state (T=400 °C and P=40 MPa). The analysis of the spectral shift of benzene in water relative to that in the gas indicates that at T=380 and 390 °C the local solvent density around benzene is likely to be depressed below the bulk density for densities near the critical density. It is found that π-hydrogen bond between benzene and water becomes evident with lowering temperature below T=340 °C. [Copyright &y& Elsevier]

UV absorption spectra of molecular oxygen were measured at pressure up to 1.5 GPa and temperature between 17 and 297 K. In the supercritical phase, an absorption band was observed in a UV region between 4.5 and 7 eV and showed an appreciable enhancement in the intensity with pressure. The absorption cross-section, σeff, of the UV band at 1.5 GPa, estimated from the molar volume obtained by present X-ray diffraction experiments, reached three orders of magnitude of previous one measured at 1.0 MPa. The observed UV absorption of high-density oxygen was attributed to the two-molecule process by an antiferromagnetic O2 pair. [Copyright &y& Elsevier]

The time-resolved absorption spectra of all-trans-spirilloxanthin (n=13) in tetrahydrofuran solution were recorded by sub-5-fs pump–probe spectroscopy in the 500–750 nm region. The difference absorption spectra and the lifetimes of the four singlet states involved were separately determined from the two-dimensional data (delay time vs. probe frequency) analyzed by the singular-value decomposition method followed by global fitting, using the title sequential model. The 1Bu+, 3Ag-, 1Bu-, and 2Ag- states were identified, and the lifetimes of the former three states were determined to be ≈10, 25 ± 2, and 140 ± 30 fs, respectively. [Copyright &y& Elsevier]

We present a combined density functional/time-dependent density functional study of the electronic structure and optical absorption spectrum of the charge-transfer sensitizer cis-[Ru(4,4′-COOH-2,2′-bpy)2(NCS)2] in water solution. To simulate the effect of different pH values, calculations have been performed for both the title complex and the corresponding tetra-deprotonated species, cis-[Ru(4,4′-COO-2,2′-bpy)2(NCS)2]4−. The experimentally observed blue-shift of the spectrum at high pH is well reproduced by our theoretical model and appears to be related to destabilization of the bipyridines π* LUMOs as a result of the increased electron density on the deprotonated carboxylic groups. [Copyright &y& Elsevier]

The microscopic model used previously for interpreting the low-energy electro-absorption (EA) spectrum of the fullerene crystal is applied to reproduce theoretically the corresponding signal at 4.5 eV. It is demonstrated that the spectral feature observed at that energy, in spite of its shape resembling that located at 3.7 eV and attributed to CT excitons, is in fact due to a Frenkel state. [Copyright &y& Elsevier]