Molecular Ions of Transient Species: Vinyl-Alcohol Cation

Vinyl alcohol 1 was prepared by thermolysis of cyclobutanol and its photoelectron spectrum was determined. I = 9.18 eV and I = 9.52 eV were found, the vibrations progression (? = 1400 cm^?1) for this lowest energy transition 1(X)→1⁺(X?) indicating significant skeletal changes in the ion. The question of the relative stability of the syn ( 1 )- vs. anti-ions ( 1 ) is discussed in the light of theoretical calculations. The energy of the second π-state of 1 ⁺ is estimated at 13.6–14.1 eV above the ground state of 1 .     

Molecular Ions of Transient Species: Vinylamine-Cation

Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured. I = 8.20 eV and I = 8.65 eV were found, the dominant vibrational progression (? = 725 cm^?1) indicating that in the course of 1(X)→1 ⁺( X? ) flattening around the N-atom occurs. The Franck-Condon profile of this band, however, suggests that a skeletal mode of ? ≈ 1400 cm^?1 (observed also in the iso-π-electronic systems vinyl-alcohol-cation and allyl radical) may also be excited. Comparison with the data for the isomer acetaldehyde-imine 2 and its cation s ⁺ shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from the neutrals to the cations.     

Probing the ultrafast photoelectron spectra of Br2 molecule

The time‐dependent‐wave‐packet method is applied to study the ionization of Br₂ molecule with four ionization processes. The ground state absorption makes the photoelectron to be left in the three final ionic states: Br (X²∑), Br (A²∏_u), and Br (B²∑), and each population of these ionic states is related with the laser intensities. The information of the dissociation can be got by analyzing the photoelectron features of the transient wave packet, which also suggests that an ionization process occurs during the dissociation, and the Br atoms that mainly resulted from the dissociation of Br₂ (C¹∏_u) are ionized at later time delays as the dissociation is nearly complete. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

An Ab initio theoretical investigation on the geometrical and electronic structures of BAun−/0 (n = 1–4) clusters

An ab initio theoretical investigation on the geometrical and electronic structures and photoelectron spectroscopies (PES) of BAu_n^?/0 (n = 1–4) auroboranes has been performed in this work. Density functional theory and coupled cluster method (CCSD(T)) calculations indicate that BAu (n = 1–4) clusters with n‐Au terminals possess similar geometrical structures and bonding patterns with the corresponding boron hydrides BH. The PES spectra of BAu (n = 1–4) anions have been simulated computationally to facilitate their future experimental characterizations. In this series, the T_d BAu anion appears to be unique and particularly interesting: it possesses a perfect tetrahedral geometry and has the highest vertical electron detachment energy (VDE = 3.69 eV), largest HOMO‐LUMO gap (ΔE_gap = 3.0 eV), and the highest first excitation energy (E_ex = 2.18 eV). The possibility to use the tetrahedral BAu unit as the building block of Li⁺[BAu₄]^? ion‐pair and other [BAu₄]^?‐containing inorganic solids is discussed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Comparison of theory and experiment for excited singlet states of the H2 molecule

This paper presents a survey of published and unpublished ab initio calculations of the vibrational structures of the ten lowest electronic singlet states of the hydrogen molecule up to the H(n = 1) + H(n = 2) dissociation limit. The data are based on adiabatic potential functions (clamped-nuclei electronic energies and nuclear-mass-dependent diagonal corrections). Nonadiabatic coupling has been treated ab initio within the five states. of ¹Λ symmetry (X,EF, GK, HH?) and ¹Σ I.¹Π_g. The accuracies of the theoretical energies are determined by comparisons with experimental data for H₂, HD, and D₂. The level shifts and predissociation probabilities of the excited ¹Σ states, generated by nonadiabatic coupling with the discrete and continuous vibrational structure of the ground state, and radiative properties have also been calculated.     

Correlated n1,3S states for coulomb three‐body systems

n^1,3S (n = 1 ? 4) states for atomic three‐body systems are studied with the Angular Correlated Configuration Interaction method. A recently proposed angularly correlated basis set is used to construct, simultaneously and with a single diagonalization, ground and excited states wave functions which: (i) satisfy exactly Kato cusp conditions at the two‐body coalescence points; (ii) involve only linear parameters; (iii) show a fast convergency rate for the energy; and (iv) form an orthogonal set. The efficiency of the method is illustrated by the study a variety of three‐body atomic systems [m m m] with two negatively charged light particles, with diverse masses m and m, and a heavy positively charged nucleus m. The calculated ground 1¹S and excited n^1,3S (n = 2 ? 4) state energies are compared with those given in the literature, when available. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Explicit expression of the franck–condon factors in terms of the potentials of the two states

The calculus of the overlap integral for two states represented by the vibrational wave functions ψ and ψ is reduced to that of the Franck–Condon integral ?(0, x) = ∫ ψψ (t) dt. It is proved that for “numerical potentials” (as well as for a Dunham potential), this integral is given on each interval by a simple analytic expression in terms of the two potentials. The Franck–Condon factors are well determined by “coupling constants” related uniquely to the coordinates of the turning points of the potentials. An application to the band system BII? XΣ of Nα₂ is compared with the usual numerical methods.     

Charge stripping C

Measurements of the translational energy loss accompanying the charge-stripping reactions M⁺+N→M²⁺+N+e⁻ and M²⁺+N→M³⁺+N+e⁻ have been performed for C, C and C, C respectively. The energy nesessary to remove the second electron from Buckminsterfullerene was determined, Q=IE(C→C=12.25±0.5 eV.     

Reaction mechanism of cysteine proteases model compound HSH with diketone inhibitor PhCOCOCH3−nXn, (X = F,Cl, n = 0, 1, 2)

Caspases are a family of cysteine proteases, which play a crucial role in apoptosis and inflammation. The reaction mechanisms involving the cysteine proteases model compound HSH with diketone (PhCOCOCH_3‐nX_n, (X = F, Cl, n = 0, 1, 2) substrate have been studied using B3LYP/6‐311+G* level of density functional theory method. The harmonic vibrational frequencies were calculated at the same level of theory used for the characterization of stationary points and zero‐point vibrational energy corrections. The condensed Fukui functions have been calculated to find the favorable reactive site for the electrophilic (f), nucleophilic (f), and radical (f) attacks in the reactants. The transition states were connected with reactants, intermediate, and products, and the minimum energy paths have been confirmed through intrinsic reaction coordinate calculation. The potential energy barrier between each step of the reactions has been calculated to find the most favorable reaction path. The binding nature of cysteine model compound with diketone substrate has been studied through the interaction energies, bond lengths, electron density, natural bond orbital, and atoms in molecules theory analysis. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Franck-Condon simulation of the photoelectron spectrum of AsCl₂ and the photodetachment spectrum of AsCl ₂⁻ employing UCCSD(T)-F12a potential energy functions: IE and EA of AsCl₂

The currently most reliable theoretical estimates of the adiabatic ionization energies (AIE₀) from the X?²B₁ state of AsCl₂ to the X?¹A₁ and ã³B₁ states of AsCl, and the electron affinity (EA₀) of AsCl₂, including ΔZPE corrections, are calculated as 8.687(11), 11.320(23), and 1.845(12) eV, respectively (estimated uncertainties based on basis‐set effects at the RCCSD(T) level). State‐of‐the‐art ab initio calculations, which include RCCSD(T), CASSCF/MRCI, and explicitly correlated RHF/UCCSD(T)‐F12x (x = a or b) calculations with basis sets of up to quintuple‐zeta quality, have been carried out on the X?²B₁ state of AsCl₂, the X?¹A₁, ã³B₁, and ùB₁ states of AsCl, and the X?¹A₁ state of AsCl. Relativistic, core correlation and complete basis‐set (CBS) effects have been considered. In addition, computed UCCSD(T)‐F12a potential energy functions of relevant electronic states of AsCl₂, AsCl, and AsCl were used to calculate Franck–Condon factors, which were then used to simulate the valence photoelectron spectrum of AsCl₂ and the photodetachment spectrum of AsCl, both yet to be recorded. Lastly, we have also computed the AIE and EA values for NCl₂, PCl₂, and AsCl₂ at the G4 level and for SbCl₂ at the RCCSD(T)/CBS level. The trends in the AIE and EA values of the group V pnictogen dichlorides, PnCl₂, where Pn = N, P, As, and Sb, were examined. The AIE and EA of PCl₂ were found to be smaller than those of AsCl₂, contrary to the order expected from the IE values of P and As. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Multi‐channel coupling effects for electronic excitations leading to the b3∑, a3∑, and c3∏u states of H2

In this work we use the unitarized distorted wave method to study the effect of multi‐channel coupling on the calculated electronic excitation cross sections in H₂. Specifically, such an effect for electronic excitations leading to the excited states b³∑, a³∑, and c³∏_u for incident energies varying from 15 to 60 eV is studied. Our results have shown that converged cross sections can be obtained with the inclusion of only triplet intermediate states, except for energies near the excitation thresholds, where the inclusion of singlet intermediate states is important. Also, convergence improves with increasing energies for all excitations considered. Comparison of our calculated cross sections with available experimental and other theoretical results is encouraging. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Density functional theory study of geometry and stability of small Zrn (n = 2–10) clusters

Geometric structures, electronic properties, and stabilities of small Zr_n and Zr (n = 2–10) clusters have been investigated using density functional theory with effective core potential LanL2DZ basis set. For both neutral and charged systems, several isomers and different multiplicities were studied to determine the lowest energy structures. Many most stable states with high symmetry were found for small Zr_n clusters. The most stable structures and symmetries of Zr clusters are the same as the neutral ones except n = 4 and 7. We found that the clusters with n > 3 possess highly compact structures. The clusters are inclined to form the caged‐liked geometry containing pentagonal structures for n > 8, which is in favor of energy. From the formation energy and second‐order energy difference, we obtained that 2‐, 5‐, 7‐atoms of neutral and 4‐, 7‐atoms cationic clusters are the magic numbers. Furthermore, the highest occupied molecular orbital‐lowest unoccupied molecular orbital gaps display that the Zr₃, Zr₆, Zr, and Zr are more stable in chemical stability. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Density functional calculations of structures and ionization energies for heavy group V cluster anions

The structure and electronic structure of heavy-group V cluster anions (Sb, Bi) are calculated with density functional methods within the local spin density approximation (LSDA ). The influence of gradient corrections of the exchange and correlation energy is investigated. The calculated vertical and adiabatic ionization energies are in very good agreement with data from photoelectron spectroscopy (PES ) for Sb, whereas the relatively large deviations for Bi can be reduced by the consideration of relativistic effects in a scalar-relativistic manner. Concerning the structures, a strong similarity to the corresponding P clusters was found. In particular, the negatively charged pentamers are planar rings (with similarities to the aromatic [C₅H₅]^? anion) with especially high ionization energies. © 1995 John Wiley & Sons, Inc.     

The formation of highly excited H in the reaction H2+(v) + H2 → H + H

A quasiclassical trajectory surface hopping method has been used to study H(v) + H₂ → H + H for v = 0, 3, 7, 10, 13, and 17 with an emphasis on determining the H internal energy and angular momentum distributions for high v. For v = 13 and 17, significant cross sections are found for producing H at energies above its dissociation energy. An average metastable H lifetime of 11.5 ps for v = 13 and 4.7 ps for v = 17 is found, but there is also a much longer lived component to the lifetime distributions that is more important for v = 13 than for v = 17. Some of the longer lived metastables correspond to high angular momentum orbiting states of H, but other sources of metastability are also present.     

Incidence of the relativistic corrections in electronic properties of 5d compounds: MS–Xα Calculations on hexachloroiridates (III and IV) and tungsten trioxide

Multiple-scattering–X_α (MS –X_α) calculations have been performed on IrCl, IrCl, and WO clusters. Relativistic calculations have been performed by the inclusion of the approximation of Wood and Boring in the MS –X_α method, i.e., mass–velocity and Darwin terms are taken into account self-consistently, while the effects of the spin–orbit operator are estimated by first-order perturbation theory. The strong contraction of s and p orbitals can be seen on selected displays of radial wave functions and significant changes in the energy diagrams between the nonrelativistic and the relativistic calculations can be obtained. The comparison with photoemission spectra clearly shows the necessity of including relativistic corrections in the calculations. The calculated spin–orbit parameters are in agreement with experiment for core levels, while a strong dependence of the spin–orbit parameters on the one electron energies is pointed out; this dependance is unconnected from the atomic contributions to the molecular orbitals.     

Length dependence of the optical transition energies of the exactly solvable Hubbard model for linear polyenes

Some accurate results on the length dependence of the excitation energies from the ground state to ionic excited states in the Hubbard model of linear polyenes are obtained based on the method of Lieb and Wu. To this end, it is first shown that singly ionic excited states with “plus” alternancy symmetry in the Hubbard model are described by the wave functions in which the two electron operator [∑(?)ⁿCC] is acted on (N ? 2)-electron covalent eigenstates. Then by solving the Lieb-Wu equations the exact excitation energies of the lowest ionic state, which corresponds to the E state in this model, are calculated for systems with up to 50 electrons. The result, together with a correction for the end effect, indicates that the excitation energies do not decrease as 1/N but converge to the limiting value more rapidly when the number of electrons N becomes large.     

The spin-density-functional formalism for quantum mechanical calculations: Test on diatomic molecules with an efficient numerical method

We have applied the spin-density-functional (SDF ) formalism with the local-spin-density (LSD ) approximation to a number of small molecules with the primary aim of testing the approximation for molecular applications. A new numerical method to solve the one-electron wave equation is developed, utilizing the special features of the SDF formalism. We have calculated energy curves, dissociation energies, and equilibrium distances for some diatomic molecules [H (²Σ, ²Σ), H₂(¹Σ, ³Σ), He (¹Σ), and He₂(¹Σ)] and the vibrational frequencies of H₂. The deviations from the experimental results are typically 1/2 eV for the energies and ≤ 0.1 Å for the distances. We discuss the LSD approximation using the concept of an exchange-correlation hole and make predictions about the applicability to other molecules. The LSD approximation is compared with the Hartree-Fock and multiple-scattering-Xα methods and some difficulties in the latter methods are pointed out. It is argued that the SDF formalism within the LSD approximation has physical advantages compared to the Hartree-Fock and Xα methods and that it should provide a simple and useful method for a broad range of applications.     

Role of anions in the polymerization of 2,5‐dimethoxyaniline in the presence of poly(styrene sulfonic acid)

Poly(2,5‐dimethoxyaniline) (PDMA)–Ag composites were successfully obtained through the oxidative polymerization of 2,5‐dimethoxyaniline in poly(styrene sulfonic acid) with CH₃SO₃Ag and AgNO₃ as oxidants. In situ ultraviolet–visible spectroscopy results showed that the growth rate of PDMA was strongly affected by CH₃SO and NO. The coupling reaction of PDMA and NO was proposed to explain the lower growth rate of PDMA with AgNO₃ as the oxidant in comparison with CH₃SO₃Ag. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to validate the proposed coupling reaction through the monitoring of the side products and oxidized state of PDMA. The results showed that there were more side products and lower oxidized states for the composite structure in the presence of NO than in the presence of CH₃SO, and this agreed with the proposal. Transmission electron microscopy showed that the Ag nanoparticles had almost the same size, regardless of the anions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6624–6632, 2006     

Ab initio characterization of several states of nitroxylium (NO). Comparison of fragmentation energies of nitroxylium,nitroxyl (NO3), and nitrate

Ab initio calculations have been performed at the self-consistent field (HF) level, and its perturbative extensions up to fourth-order (MPn), for several electronic states of nitroxylium (NO) as well as for a large number of reference species. Geometries are optimized at the HF/DZ and HF/DZP levels (double zeta and double zeta plus polarization bases). The ground state is found to be the D_3h ¹A₁′ state, with the C_2v ¹A₁ (closed Y) state higher by 0.94 eV. The relationship between adding electrons or oxygen atoms to NO⁺ and NO is explored, especially in relation to fragmentation energies of NO (q = 0 or 1). A comparison is drawn between NO and two isoelectronic species, CO₃ and C(CH₂)₃, where no surprises are found.     

Perturbational calculation of the exchange forces in the two lowest states of the hydrogen molecule

The interaction energies in the ground (X¹Σ) and the first excited (b³Σ)states of the hydrogen molecule were calculated using the modified Jansen and Byers Brown perturbation method. Calculations were performed for nine values of the internuclear distance R in the range 5 a.u. ≦ R ≦ 9 a.u. The present results were compared with the interaction energies calculated by four other perturbation methods as the expectation values of the H – E⁰ operator with the function accurate up to the first order. The results show that the method can give satisfactory values of the interaction energies.