Ground State Values Research Articles

Solvatochromic shift and estimation of dipole moment of quinine sulfate

The absorption and fluorescence spectra of quinine sulfate (QS) have been recorded at room temperature in wide range of solvents of different polarities. The ground-state dipole moment of QS was obtained from quantum mechanical calculations and the excited state dipole moment of QS was estimated from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. Higher value of dipole moment has been observed for excited state as compared to the corresponding ground state value and this is attributed to the more polar excited state of QS.

Relativistic mean field inA≈80nuclei and low-energy proton reactions

Relativistic mean-field calculations were performed for a number of nuclei in the mass $A\ensuremath{\sim}80$ region. Ground-state binding energy, charge radius, and charge density values were compared with experiment. The optical potential was generated folding the nuclear density with the microscopic nuclear interaction DDM3Y. $S$ factors for low-energy ($p,\phantom{\rule{-0.16em}{0ex}}\ensuremath{\gamma}$) and ($p,\phantom{\rule{-0.16em}{0ex}}n$) reactions were calculated and compared with experiment.

Theoretical investigations of the physical properties of zircon-type YVO4

The crystal structure, electronic properties, elastic properties, hardness and thermodynamic properties of the laser host material zircon-type YVO4 are studied using the pseudopotential plane wave method within the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated ground state values such as lattice parameter, bulk modulus and its pressure derivative, the band structure and densities of states were in favorable agreement with previous works and the existed experimental data. The elastic constants Cij, the aggregate elastic moduli (B, G, E), Poisson's ratio and elastic anisotropy have been investigated. In YVO4, V–O bonds with shorter bond length and larger Mulliken population make great contribution to hardness than Y–O bonds. Using quasi-harmonic Debye model considering the phonon effects, bulk modulus, heat capacity and thermal expansion coefficient of YVO4 are calculated within a range of 0–6GPa and 0–1200K.

Addition of Hydrocarbons to H–Si(100) in Extra-Mild Conditions: A Novel Mechanism Valid for Single and Multiple C–C Bonds

The establishment of strong C–Si bonds connecting a molecular moiety to the Si surface has been widely reported with different synthetic recipes, but general and reliable reaction mechanisms have not been described yet for the distinct chemical routes. The coupling of a suitable functional group in the molecule with a reactive termination of the Si surface is a prerequisite for the reaction to happen, and the presence of a C–C multiple bond has long been thought to be necessary for an extra-mild attachment, as in the visible light induced organics–Si anchoring reaction. In this paper, the addition of saturated and unsaturated hydrocarbons to the hydrogenated Si(100) surface has been modeled by density functional theory calculations. The aim is to describe a mechanism allowing for the addition of single C–C bonds to Si(100) and the addition of C═C bonds with preservation of the unsaturation. In fact, both these reactions have been observed recently, but they are not explained by radical-initiated hydrosilylation, the more commonly invoked mechanism for this class of processes. The mechanism proposed here is described by computing the reaction path in the ground state and recomputing the energies in the first excited state. Both for saturated hydrocarbons and for unsaturated hydrocarbons we found that the activation barriers in the excited state reduce to about 60–65% of their ground state value. The barrier lowering is explained in terms of the frontier orbital change along the reaction path. These findings can explain why visible light can activate the formation of a C–Si bond, even if it is not energetic enough to break a H–Si bond.

Synthesis, Microwave Spectrum, and Dipole Moment of Allenylisocyanide (H2C═C═CHNC), a Compound of Potential Astrochemical Interest

An improved synthesis of a compound of potential astrochemical interest, allenylisocyanide (H(2)C═C═CHNC), is reported together with its microwave spectrum, which has been investigated in the 8-120 GHz spectral range to facilitate a potential identification in interstellar space. The spectra of the ground vibrational state and of five vibrationally excited states belonging to three different vibrational modes have been assigned for the parent species. A total of 658 transitions with a maximum value of J = 71 were assigned for the ground state and accurate values obtained for the rotational and quartic centrifugal distortion constants. The spectra of five heavy-atom ((13)C and (15)N) isotopologues were also assigned. The dipole moment was determined to be μ(a) = 11.93(16) × 10(-30) C m, μ(b) = 4.393(44) × 10(-30) C m, and μ(tot) = 12.71(16) × 10(-30) C m. The spectroscopic work has been augmented by theoretical calculations at the CCSD/cc-pVTZ and B3LYP/cc-pVTZ levels of theory. The theoretical calculations are generally in good agreement with the experimental results.

Infrared spectra of acetylene dimers and acetylene–nitrogen: (DCCD) 2, H-bonded DCCD–HCCH, and DCCD–NN in the 4.1 μm region

Infrared spectra of the weakly-bound T-shaped acetylene dimers DCCD–DCCD and DCCD–HCCH are studied in the region of the DCCD ν 3 fundamental (∼2440 cm −1) using a pulsed supersonic slit-jet expansion and a tunable diode laser probe. The K a = 0 ← 1 and 1 ← 0 subbands, corresponding to the vibration of the DCCD monomer at the “top” of the T, are analyzed. Compared to the analogous spectrum of HCCH–HCCH, the present results are much less perturbed. The tunneling splitting for (DCCD) 2 in the excited state is determined to be 141 MHz, a big reduction from the previously determined ground state value of 424 MHz. The dimer A rotational constants show a large apparent increase upon vibrational excitation, and we discuss whether this increase is real. The linear DCCD–NN complex is also observed as an impurity in the spectrum, and it too is found to be unperturbed, in contrast with HCCH–NN.

Photochemical Properties and Reactions with Biomolecules of 4'-N-Acetyl Derivative of Norfloxacin

Abstract The photochemical properties of 4'-N-acetyl derivative of norfloxacin (ANFX) were investigated in different solutions. Both UV-Vis absorption and the quantum yields of excited states are pH-dependent, and pK a value of ground state for the protonation of 3-carboxylic group was determined to be 6.5 ± 0.2. Pulse radiolysis and laser flash photolysis experiments were carried out to characterize transient species of ANFX and to investigate reactions with tryptophan (TrpH) and 2'-seoxyguanosine-5'-monophosphoric acid disodium salt (dGMP). The ANFX undergoes the photoejection of electron by a mixed mechanism of one-photon and two-photon processes. Under moderate laser energy conditions, two-photon process is predominantly. The ANFX radical dianion (ANFX(–H)·2−) formed in reaction with eaq − is characterized by the absorption around 370 nm, and the rate constant was determined to be 1.2 × 1010 dm3 mol−1 s−1. The 3ANFX(–H)−∗ is able to oxidize TrpH and dGMP with bimolecular rate constants of 5.4 × 108 and 9.5 × 106 dm3 mol−1 s−1, respectively. The ANFX(–H)·2− and the oxidized radicals of TrpH and dGMP were observed directly. Under aerobic conditions, the photo-oxidations involve both type I and type II mechanisms.

Effect of positional substitution of amino group on excited state dipole moments of quinoline

The effect of positional substitution of amino group on the ground and excited state dipole moments of quinoline ring has been investigated using solvatochromic shift methods. The excited state dipole moments of 5aminoquinoline (5AQ) and 3aminoquinoline (3AQ) have been estimated from the spectral data in different non-polar, polar aprotic and polar protic solvents using Bakhshiev and Kawski–Chamma–Viallet equations. It has been observed that both grounds as well as excited state dipole moments for 5AQ are higher than those for 3AQ by approximately a factor of two. Higher values of the excited state dipole moments for both 3AQ and 5AQ as compared to corresponding ground state values have been attributed to intramolecular charge transfer processes. The role of specific solute–solvent interaction on excited state dipole moment in addition to the general solvent effects has been discussed.

Effect of Roasting Conditions on Hardness, Moisture Content and Colour of Pistachio Kernels

Roasting of whole-kernels is an important step in the production of pistachio paste. The effect of hot air roasting temperatures (90-190°C) and times (5-65 min) on the hardness, moisture content and colour attributes (‘L’, ‘a’ and ‘b’ values and yellowness index) of both whole-kernel and ground-state were investigated using response surface methodology (RSM). Increases in roasting temperature and time caused a decrease in all the responses except for ‘a’ value of ground-state. The interaction and quadratic models sufficiently described the changes in the hardness and colour values, respectively. The result of RSM analysis showed that hardness and colour attributes (‘L’ and ‘b’ values, yellowness index) of kernels and ‘a’ value of ground-state could be used to monitor the roasting quality of whole-kernels. This study showed that the recommended range of roasting temperature and time of whole-kernel for the production of pistachio paste were 130-140°C and 30-40 min, respectively.

The high hydrostatic pressure effect on shallow donor binding energies in GaAs–(Ga, Al)As cylindrical quantum well wires at selected temperatures

We have presented the behavior of a shallow donor impurity with binding energy in cylindrical-shaped GaAs/Ga 0.7Al 0.3As quantum well wires under high hydrostatic pressure values. Our results are obtained in the effective mass approximation using the variational procedures. In our calculations, we have not considered the pressure related Γ−X crossover effects. The hydrostatic pressure dependence on the expectation value of ground state binding energy is calculated as a function of wire radius at selected temperatures. We have also discussed the effects of high hydrostatic pressure and temperature on some physical parameters such as effective mass, dielectric constant, and barrier height. A detailed analysis of these calculations has proved that the effective mass is the most important parameter, which explains the dependency of donor impurity binding energies on the high hydrostatic pressure values.

Rovibrational spectrum and potential energy surface of the N 2–N 2O van der Waals complex

The rovibrational spectrum of the N 2–N 2O van der Waals complex has been recorded in the N 2O ν 1 region (∼1285 cm −1) using a tunable diode laser spectrometer to probe a pulsed supersonic slit jet. The observed transitions together with the data observed previously in the N 2O ν 3 region are analyzed using a Watson S-reduced asymmetric rotor Hamiltonian. The rotational and centrifugal distortion constants for the ground and excited vibrational states are accurately determined. The band-origin of the spectrum is determined to be 1285.73964(14) cm −1. A restricted two-dimensional intermolecular potential energy surface for a planar structure of N 2–N 2O has been calculated at the CCSD(T) level of theory with the aug-cc-pVDZ basis sets and a set of mid-bond functions. With the intermolecular distance fixed at the ground state value R = 3.6926 Å, the potential has a global minimum with a well depth of 326.64 cm −1 at θ N 2 = 11.0° and θ N 2 O = 84.3° and has a saddle point with a barrier height of 204.61 cm −1 at θ N 2 = 97.4° and θ N 2 O = 92.2°, where θ N 2 ( θ N 2 O ) is the enclosed angle between the N–N axis (N–N–O axis) and the intermolecular axis.

Synthesis and Application of New Ruthenium Complexes Containingβ-Diketonato Ligands as Sensitizers for Nanocrystalline TiO2Solar Cells

Five heteroleptic ruthenium complexes having differentβ-diketonato ligands, [Ru(tctpy)(dppd)(NCS)] (1), [Ru(tctpy)(pd)(NCS)] (2), [Ru(tctpy)(tdd)(NCS)] (3), [Ru(tctpy)(mepd)(NCS)] (4), and [Ru(tctpy)(tmhd)(NCS)] (5), where tctpy = 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine, pd = pentane-2,4-dione, mepd = 3-methylpentane-2,4-dione, tmhd = 2,2,6,6-tetramethylheptane-3,5-dione, tdd = tridecane-6,8-dione, and dppd = 1,3-diphenylpropane-1,3-dione, were synthesized and characterized. These heteroleptic complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range extending up to 950 nm. The low-energy absorption bands and theE (Ru3+/2+) oxidation potentials in these complexes could be tuned to about 15 nm and 110 mV, respectively, by choosing appropriateβ-diketonate ligands. Molecular orbital calculation of complex1shows that the HOMO is localized on the NCS ligand and the LUMO is localized on the tctpy ligand, which is anchored to the TiO2nanoparticles. Theβ-diketonato-ruthenium(II)-polypyridyl sensitizers, when anchored to nanocrystalline TiO2films for light to electrical energy conversion in regenerative photoelectrochemical cells, achieve efficient sensitization to TiO2electrodes with increasing activity in the order5<4<3≈2<1. Under standard AM 1.5 sunlight, the complex1yielded a short-circuit photocurrent density of 16.7 mA/cm2, an open-circuit voltage of 0.58 V, and a fill factor of 0.64, corresponding to an overall conversion efficiency of 6.2%. A systematic tuning of HOMO energy level shows that an efficient sensitizer should possess a ground-state redox potential value of >+.53 V versus SCE.

A Scheme for Calculating Atomic Structures beyond the Spherical Approximation

We present a scheme for calculating atomic single-particle wave functions and spectra with taking into ac-count the nonspherical effect explicitly. The actual calculation is also performed for the neutral carbon atom within the Hartree-Fock-Slater approximation. As compared with the conventional atomic structure of the spherical approximation, the degenerate energy levels are split partially. The ground state values of the total orbital and spin angular momenta are estimated to be both about unity, which corresponds to the term P3PP in the LS-multiplet theory. This means that the nonspherical effect may play an essential role on the description of the magnetization caused by the orbital polarization.

Self-assembled decanuclear NaI2MnII4MnIII4 complexes: from discrete clusters to 1-D and 2-D structures, with the MnII4MnIII4 unit displaying a large spin ground state and probable SMM behaviour

The synthesis, magnetic characterization and X-ray crystal structures are reported for five new manganese compounds, [Mn(III)(teaH(2))(sal)]·(1/2)H(2)O (1), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(4)]·6MeOH (2), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·7MeOH (3), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·2MeOH·Et(2)O (4) and [K(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(H(2)O)(2)](n)·5MeOH (5). Complex 1 is a mononuclear compound, formed via the reaction of Mn(NO(3))(2)·4H(2)O, triethanolamine (teaH(3)) and salicylic acid (salH(2)) in a basic methanolic solution. Compound 2 is a mixed-valent hetero-metallic cluster made up of a Mn(8)Na(2) decanuclear core and is formed via the reaction of sodium azide (NaN(3)) with 1. Compounds 3-5 are isolated as 1- or 2-D coordination polymers, each containing the decanuclear Mn(8)M(2) (M = Na(+) or K(+)) core building block as the repeating unit. Compound 3 is isolated when 1 is reacted with NaN(3) over a very short reaction time and forms a 1-D coordination polymer. Each unit displays inter-cluster bridges via the O-atoms of teaH(2-) ligands bonding to the sodium ions of an adjacent cluster. Increasing the reaction time appears to drive the formation of 4 which forms 2-D polymeric sheets and is a packing polymorph of 3. The addition of KMnO(4) and NaN(3) to 1 resulted in compound 5, which also forms a 1-D coordination polymer of the decanuclear core unit. The 1-D chains are now linked via inter-cluster potassium and salicylate bridges. Solid state DC susceptibility measurements were performed on compounds 1-5. The data for 1 are as expected for an S = 2 Mn(III) ion, with the isothermal M vs. H data being fitted by matrix diagonalization methods to give values of g and the axial (D) and rhombic (E) zero field splitting parameters of 2.02, -2.70 cm(-1) and 0.36 cm(-1) respectively. The data for 2-5, each with an identical Mn(II)(4)Mn(III)(4) metallic core, indicates large spin ground states, with likely values of S = 16 (±1) for each. Solid state AC susceptibility measurements confirm the large spin ground state values and is also suggestive of SMM behaviour for 2-5 as observed via the onset of frequency dependent out-of-phase peaks.

Synthesis, spectrophotometric pH titrations and DNA binding properties of a cyclometalated iridium(III) complex of tetrapyrido[3,2- a:2′,3′- c:3″,2″- h:2‴,3‴- j]phenazine

A new cyclometalated iridium(III) complex [Ir(ppy) 2(tpphz)]Cl {Hppy = 2-phenylpyridine and tpphz = tetrapyrido[3,2- a:2′,3′- c:3″,2″- h:2‴,3‴- j]phenazine} has been synthesized and characterized. The pH effects on UV–vis absorption spectra have been studied, and three ground-state acidity ionization constant values have been derived. The calf thymus (ct) DNA binding properties of the complex have also been investigated with UV–vis absorption spectrophotometric titrations, DNA competitive binding with ethidium bromide, DNA melting experiments, viscosity measurements, and density functional theory calculations. The complex was demonstrated to act as a DNA intercalator with a binding constant of (9.29 ± 1.26) × 10 5 M −1 more than one order of magnitude greater than that previously reported for DNA intercalator of [Ir(ppy) 2(dppz)] +.

Laser effects in excitons in a quantum wire

AbstractWe investigate the effects of laser field intensity over the ground state binding energy of light and heavy hole excitons confined in GaAs/Ga1−xAlx As cylindrical quantum wire. We have applied the variational method using 1s‐hydrogenic wave functions, in the framework of the single band effective mass approximation with the spatial dielectric function. The polaronic effects are included in the calculation to compute the exciton binding energy as a function of the wire radius for different field of laser intensity. The valence‐band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. The dressed laser donor binding energies are calculated and compared with the results of binding energy of excitons. The results show that (i) the binding energy is found to increase with decrease with the wire radius, and decrease with increase with the value of laser field amplitude, (ii) the heavy‐hole exciton in a cylindrical quantum wire is more strongly bound than the light‐hole exciton, (iii) the values of ground state binding energy for the laser field amplitude α0 = 10 Å resemble with the values of heavy hole exciton binding energy, and (iv) the binding energy of the impurity for the narrow well wire is more sensitive to the laser field amplitude. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Effect of anisotropic and isotropic solvent on the dipole moment of coumarin dyes

The ground state ( μ g) and the excited state ( μ e) dipole moments of two coumarin laser dyes, coumarin 440 and 460, were studied at room temperature in various solvents, viz., general solvents, alcohols and liquid crystals at 298 K. In this work, we report dipole moment of laser dyes in different anisotropic (liquid crystal) and isotropic environments for understanding the effects of environments on the molecular dipole moment and comparing them. Ground and excited state dipole moments of coumarin dyes were evaluated by means of solvatochromic shift method. It was observed that dipole moment values of excited states ( μ e) were higher than the corresponding ground state values ( μ g) in all media.

The high-resolution, jet-cooled infrared spectrum of pentafluoroethane

The jet-cooled spectrum of pentafluoroethane (C 2HF 5) has been recorded between 1100 and 1325 cm −1 at a resolution of 0.0022 cm −1. A rotational temperature of approximately 10 K was achieved by expanding 50 Torr of C 2HF 5 in 500 Torr of helium. Transitions belonging to five different fundamental vibrations have been assigned and fit to a Watson Hamiltonian: the ν 3 band at 1309.880494(189) cm −1, ν 4 at 1200.734645(67) cm −1, ν 5 at 1142.78147(33) cm −1, ν 13 at 1223.334098(115) cm −1, and ν 14 at 1147.394185(163) cm −1. The fit of the ν 4 band has an rms deviation of 0.000436 cm −1 compared to the uncertainty in the experimental line position of 0.0002 cm −1. Satisfactory fits were achieved for the other four bands ( ν 3, ν 5, ν 13, ν 14) at this cold temperature, with most of the centrifugal distortion constants fixed at the ground state values. Joint fits with previous work were attempted for the ν 4 and ν 13, successfully in the former case and unsuccessfully in the latter.

Solvent effects and photophysical studies of ADS560EI laser dye

The ground state (μg) and the excited state (μe) dipole moments of a laser dye ADS560EI is estimated in various solvents by Lippert, Backshieve, Kawski-Chamma-Viallet, McRae and Suppan equations using the variation of stokes shift with the solvent dielectric constant and refractive index. The excited state dipole moments were also calculated by using the variation of stokes shift with microscopic solvent polarity parameter (). It was observed that the dipole moment values of excited state (μe) were higher than corresponding ground state values (μg), indicating a substantial redistribution of the π-electron densities in a more polar excited state than the ground state. The rotational reorientation of this probe molecule has also been examined in various solvents. It is observed that the increase in viscosity of the solvent is responsible for the increase in the rotational relaxation time of the probe molecule. Key words: Stokes shift, excited state, ground state, dipole moment, reorientation time.

ChemInform Abstract: Torsion-Rotation Absorption Line Assignments in the Symmetric CH- Stretch Fundamental of Methanol.

Abstract The symmetric CH-stretch fundamental band of methanol vapor has been examined between 2800 and 2880 cm −1 by means of a 1.25-m path difference Fourier transform spectrometer. Ten parallel-type subbands have been identified—eight of these arise from torsional states with principal quantum number n = 0 and two with n = 1. Most of these subbands exhibit strong rotational perturbations. An approximate analysis of the subband origins yields a band center at 2843.39 cm −1 and a hindering potential barrier height in the excited state of 379 cm −1 as compared with the ground state value of 373 cm −1 .