Potential energy curves for NiH and NiH2

The potential energy curves for the NiH and linear HNiH molecules resulting from the 3d⁸4s² and 3d⁹4s configuration of nickel are calculated using the unrestricted Hartree–Fock and perfect pairing generalized valence bond methods. NiH bonding in the 3d⁸4s² configuration is by means of an sp hybrid orbital which comes from the 4s² shell leaving a singly occupied nonbonding orbital free to bond to another hydrogen atom. The bond to the 3d⁹4s configuration contains primarily the 4s orbital leaving an empty orbital in the nickel 3d shell which in turn bonds very weakly with another hydrogen. These results are compared to similar studies of the hydrogen atom on Sc, Mn and Cu and some implications for hydrocarbon catalysis are considered.     

Potential energy curves of diatomic molecules from the Hill determinant method

The Hill determinant method is shown to be suitable for constructing potential energy curves of diatomic molecules. Both the Dunham and the perturbed Morse oscillator potentials are used to fit spectroscopic data. Results are shown for ionic and covalent molecules.     

Potential energy curves for Li2

A model potential method is used to calculate the potential curves of a large number of states of the lithium molecule and comparisons are made with other theoretical and experimental data. Agreement is generally satisfactory. Several bound states are predicted that have not been identified experimental including a ³Σ^?_g state that dissociates into two excited atoms.     

A simple determination of the potential energy curves and couplings for long-range charge-transfer reactions. Application to the system (ArN2)+

An original method is presented for calculating long-range energies and couplings of the two (non-adiabatic) states A⁺–B and A–B⁺ of a charge-transfer system (AB)⁺. This method is applied to the calculation of the charge-exchange cross sections in the system (ArN₂)⁺. Concerning the reaction from N₂⁺, we show that the errors made in approximating the interaction energy and the couplings do not affect strongly the values of the cross sections, that most transitions are well described by the Demkov model, and that the evolution of the cross section is governed by the radius R_D (where the coupling is equal to the separation of the states) rather than by the transition probability. We have also obtained qualitative information for the reaction from Ar⁺.     

Potential energy curves: A simple and rapid method

The true potential energy curves for different electronic states of diatomic molecules have been constructed by a simplified and modified form of the Jarmain method. To check the validity of this new procedure potential energy curves are constructed for NO⁺, VO, Si₂, AsO, AsO⁺, PF⁺, CO and Bi₂. The results are in good agreement with the Jarmain, RKRV and Lakshman and Rao methods.     

Potential energy curves and calculations of spectroscopic constants for the ground state of AlC and AlN

The density functional theory method with B3LYP/6-311++G(df,pd), B3LYP/6-311++G(2df, 2pd), and B3LYP/6-311++G(3df,3pd) basis sets is used to compute the geometrics and single point energy of aluminum carbide (AlC) and aluminium nitride (AlN) in their ground state. The Level 8.0 program is used to calculate spectroscopic constants and fit the energy potential curves. The effect of a basis set on the spectroscopic constants is discussed. The results show that the calculated potential curve matches well with the Level 8.0 fitting curve, and the calculated values of spectroscopic constants become more reliable with the improvement of the quality of basis sets. The spectroscopic constants are in good agreement with the existing experimental and theoretical values. For the first time, the reliable anharmonicity constant data of AlC are reported, which agrees so well with the experimental value.     

Potential surfaces and nonadiabatic couplings in ionic systems: A study of the (O2H)+ interactions

The adiabatic potential energy surfaces (PES ) which are most likely to be involved in the elementary mechanism presiding over charge-exchange and direct inelastic collisions between O₂ molecules and collimated beams of protons are discussed. The general behavior of Diatomics-in-molecule (DIM ) model interactions is analyzed in great detail as a function of the molecular vibrational coordinate and of the other internal nuclear coordinates. The general features of the lower two PES are discussed, and the corresponding nonadiabatic coupling terms between these surfaces are also computed and analyzed. These model results turn out to provide very useful indications on the specific dynamical features that are to be considered responsible for the inelastic, vibronic transitions observed in the target molecule during collisional experiments.     

Thermal radiation from C(N)+ and La@C(N)+

The radiative cooling of positively charged fullerene and endohedral fullerene fragments of C60, C70, C84, and La@C82 has been measured in a time-of-flight mass spectrometer. The radiative cooling is measured via its influence on the metastable decay. The emissivity extracted from the data is between 4x10(-4) and 13x10(-4). These values agree fairly well with the emissivity calculated from considering the low-energy tail of the surface plasmon. No major difference is found in the emission behavior of empty and endohedral fullerenes.     

Diagrammatic perturbation theory: Potential curves for the ground state of the carbon monoxide molecule

Diagrammatic many-body perturbation theory is used to calculate the potential energy function for the X¹ σ+ state of the CO molecule near the equilibrium nuclear configuration. Spectroscopic constants are derived from a number of curves which are obtained from calculations taken through third order in the energy. By forming [2/1] Padé approximants to the constants we obtain: r_e = 1.125 Å (1.128 Å), B_e = 1.943 cm^?1 (1.9312 cm^?1), a^B_e = 0.0156 cm^?1 (0.0175 cm^?1), W_e = 2247 cm^?1 (2170 cm^?1), W_eX_e = 12.16 cm^?1 (13.29 cm^?1), where the experimental values are given in parenthesis.     

Electronic structure of the radicals NF and NCI. I. Potential energy curves for NF

Large-scale MRD CI calculations are employed to determine the potential energy curves for the 1π⁴2π², 1π³2π³ and 5σ1π⁴2π³, 1π⁴2π6σ states of NF as well as that of the lowest state of the positive NF⁺ ion. Vertical transition energies to states up to 10 eV are given. In contrast to OZ the ;(5a → 2π) and ³(2π -> 6a) states are found below those arising from the 1π³2π³ configuration. Numerous avoided crossings between states occur, primarily at larger internuclear separations, which cause, for example, a barrier to WE' dissociation and a distinct minimum in the 1¹Σ⁺ curve.     

Electronic structure of the radicals NF and NCI. II. Potential energy curves for NCI

Large-scale MRD CI calculations are employed to determine the potential energy curves for the three lowest X³Σ⁻, a¹Δ and b¹Σ⁺ states of NCl with π^*2 configuration, for the higher states arising from σ → π^*, π → σ^* and π → π* excitation and for the ²Π ion. Numerous avoided crossings are found to occur between curves in the region of internuclear separations treated. A comparison with the corresponding curves for the radicals NF, O₂ and SO is undertaken and the basic similarities and distinctions are discussed. The curves in NF and NCl are quite similar, with generally lower energy gaps in the second-row radical; they can to a large extent be constructed from the homonuclear counterpart by mixing of g and u symmetry and by taking into account the different multiplicities in the dissociation products N + Cl or F and O + O or S.     

Potential use of the activation energy value calculated from the thermoluminescence glow curves to detect irradiated food

We herein report on the calculation of the activation energy (E _a) from the thermoluminescence (TL) glow curves performed by the initial rise method that allows us to discriminate between irradiated and non-irradiated sesame seeds. E _a values of natural TL (0.68 ± 0.03 eV) and gamma-induced TL (never lower than 0.82 ± 0.02 eV) appear as a complementary criterion to be used differentiating between irradiated and non-irradiated foodstuffs with the position and the intensity of the main peak of the TL emission. In addition, E _a values taken from irradiated sesame samples at different doses (1, 5 and 10 kGy) and stored up to 15 months after being processed were compared to a ‘positive’ Spanish blend (i.e. at least one component was commercially irradiated).     

Searching of potential energy curves for the benzene dimer using dispersion-corrected density functional theory

The present work aims to establish the utility of dispersion-corrected density functional theory for potential energy curves of the benzene dimer, a problem that has received significant attention for a long time. The interaction energies of parallel-stacked, T-shaped and parallel-displaced benzene dimer configurations have been evaluated using both dispersion- and normal gradient-corrected Perdew-Burke-Ernzerhof functionals along with Dunning's augmented correlation-consistent polarized valence triple-zeta (aug-cc-pVTZ) basis functions and compared with explicit correlation methods. The potential energy curves for the parallel-stacked and parallel-displaced benzene dimers are in excellent agreement with highly accurate coupled cluster (CCSD(T)) results, while for the T-shaped benzene dimer the dispersion-corrected results show a distinct deviation, being closer in that case to the MP2 level of results. The overestimation of interaction energy in the T-shaped dimer may be attributed to the presence of a permanent dipole moment in this configuration and indicates a structural dependence of the dispersion-corrected density functional method.     

Potential energy curves and photochemical cis-trans isomerism in styrene

Cis-trans photoisomerism of styrene is investigated from a theoretical point of view. Curves of the potential energy as a function of the rotation angle (ω) around the ethylenic bond were obtained for the ground state and a few excited states by the CIPSI PCILO method. The potential surface of the lowest excited singlet is found to have both an absolute minimum at ω = π/2 and a small relative minimum at ω = 0. These findings are consistent with the singlet mechanism for the direct cis-trans photoconversion. The origin of the two energy minima in the S₁ potential surface is explained in terms of weights of the local excitations in the zero-order wavefunction.     

Potential energy curves for ground and excited states of NaLi from ab initio calculations with effective core polarization potentials

Sixteen low-lying electronic states of NaLi are investigated by SCF/valence Cl calculations including core polarization effects by means of an effective potential. Spectroscopic constants are obtained with estimated uncertainties of ΔR_e ? 0.01 Å, Δω_e ? 0.6 cm^?1 and ΔD_e ? 80 cm^?1. From a comparison of experimental and theoretical G(υ) values, we suggest a ground-state dissociation energy of 7093 ± 5 cm^?1. Using our rovibrational energies and recently measured excitation lines, we are able to improve the T_e values and dissociation energies of five excited states to an accuracv of ±8 cm^?1.     

Potential energy surface for the Pd-H2 system: Comparison with matrix isolation experiments

Summary We present here those aspects of the Pd-H₂ potential energy surface that are most directly related to the questions raised by matrix isolation experiments for the formation of Pd(¹-H₂) and Pd(²-H₂) complexes. 125 points of this potential energy surface were obtained at a CI level using the CIPSI Scheme and including the order of 10⁵ configurations. Relativistic effects are included and shown not to be crucial in understanding the main features of the surfaces. The theoretical results serve to explain many features of the low-temperature experiments on the Pd-H₂ reaction, especially those concerning the spectroscopic changes observed when different noble gas supports, Kr or Xe, are utilized.On Sabbatical leave from Instituto de Física, UNAM     

Potential energy curves and spectral properties for electronic states of F2 and F+2

Potential energy (PE) curves for the Rydberg states of F₂, and for the ground and lowest two electronic states each of symmetry ²Π_g,u, ²Δ_g,u and ²Σ^±_g,u of F⁺₂, have been obtained using modest-sized configuration-interaction calculations. These PE curves have been used to calculate spectroscopic constants for the electronic states and the results agree reasonably well with the limited experimental and theoretical results previously reported. The theoretical PE curves for the Rydberg states of F₂ are found to be strongly perturbed by valence-Rydberg-ionic interactions and these perturbations appear to be responsible for certain features in recently reported electron energy-loss spectra in F₂. The corresponding electronic wavefunctions have been used to calculate the electronic transition moment, as a function of the internuclear distance, for dipole-allowed transitions between the lowest excited electron state of each symmetry and the appropriate ground electronic state. The radiative emission probabilities, natural lifetimes, and absorption oscillator strengths, for each band system, are also reported here. The predicted lifetimes for vibrational levels of the A ²Π_u of electronic state in F⁺₂ vary from 1.3–1.5 μs and agree reasonably well with the single available set of measurements. The predicted radiative lifetimes for the higher electronic states of F⁺₂ are substantially longer and fall into the range 5–100 ms.