Journal of Chemical Physics
1089-7690
0021-9606
Mỹ
Cơ quản chủ quản: American Institute of Physics , AIP PUBLISHING
Lĩnh vực:
Medicine (miscellaneous)Physical and Theoretical ChemistryPhysics and Astronomy (miscellaneous)
Các bài báo tiêu biểu
<i>Ab initio</i> study on the ground and low-lying excited states of cesium iodide (CsI) Potential energy curves (PECs) for the ground and low-lying excited states of the cesium iodide (CsI) molecule have been calculated using the internally contracted multireference configuration interaction calculation with single and double excitation method with the relativistic pseudopotentials. PECs for seven Λ-S states, XΣ+1, 2Σ+1, Σ+3, Π1, and Π3 are first calculated and then those for 13 Ω states are obtained by diagonalizing the matrix of the electronic Hamiltonian Ĥel plus the effective one-electron spin-orbit (SO) Hamiltonian ĤSO. Spectroscopic constants for the calculated ground X0+-state PEC with the Davidson correction are found to agree well with the experiment. Transition dipole moments (TDMs) between X0+ and the other Ω states are also obtained and the TDM between X0+ and A0+ is predicted to be the largest and that between X0+ and B0+ is the second largest around the equilibrium internuclear distance. The TDMs between X0+ and the Ω=1 states are estimated to be nonzero, but they are notably small as compared with those between the 0+ states. Finally, vibrational levels of the X0+ PEC for the two isotopic analogs, Cs133I and Cs135I, are numerically obtained to investigate the isotope effect on the vibrational-level shift. It has been found that the maximized available isotope shift is ∼30cm−1 around v=136.
Tập 128 Số 2 - 2008
Bonding and potential energy curves for NiH and NiH2 The MINDO/SR procedure does well in reproducing experimental observations and theoretical ab initio calculated properties of NiH and NiH2. The occupied Ni d orbitals are nonbonding and remain lower in energy than the bonding Ni s and p orbitals in both NiH and NiH2. In agreement with experiment the lowest state of NiH2 is calculated to be a triplet with σ and δ holes in the d orbitals. A number of bent metastable states of NiH2 have been found, with the geometry being influenced indirectly by the d-orbital occupancy. One triplet state with a triangular geometry can be readily formed from H2 plus Ni and is stable by 9 kcal/mol with respect to dissociation into Ni plus H2. The H–H bond is stretched and reduced in energy but is not broken. This is a highly activated H2 molecule but there is still a large activation evergy, 42 kcal/mol, to completely break the H–H bond.
Tập 80 Số 5 - Trang 2042-2048 - 1984
Addition of Symmetrical Diatomic Molecules to Benzene The reaction of hydrogen and benzene to form 1,2-dihydrobenzene is considered, and the activation energy of the reaction is calculated with various assumptions concerning directed valence. It is shown that one may calculate approximate heats of reactions by considering exchange integrals only between electrons on neighboring atoms in a molecule, but this is not possible in calculating activation energies. The hydrogenation of benzene is considered as an eight electron problem, and the system serves to illustrate the degree of simplification of the secular equation arising from the symmetry of the system. The matrix elements of the factored equation are calculated. Activation energies of the reactions involved in the adsorption of H2 and C6H6 on Ni have been calculated and lead one to expect that the reaction might be achieved more easily catalytically.
Tập 3 Số 1 - Trang 49-55 - 1935
Fourier transform emission spectroscopy of the jet-cooled CCN free radical The à 2Δ–X̃ 2Π electronic transition of the CCN free radical was observed in emission with a high-resolution Fourier transform spectrometer. The CCN was jet-cooled in a corona-excited supersonic jet expansion of diazoacetonitrile (HC(N2)CN) in helium. From the 000–000, 000–001, 000–002, and 000–100 vibronic bands spectroscopic constants were derived including the ground-state vibrational frequencies, ν3=1050.7636(6), 2ν3=2094.8157(18), and ν1=1923.2547(69) cm−1.
Tập 92 Số 4 - Trang 2244-2247 - 1990
Rotational analysis of the 0 band of the <i>A</i>̃ 3<i>E</i>–<i>X</i>̃ 3<i>A</i>2 system of methylnitrene The optical emission spectrum of the methylnitrene radical has been observed at a resolution of 0.07 cm−1. Transitions to subbands with K up to 3 in the X̃ 3A2 ground state were observed and a full rotational analysis carried out. Comparison of the structural information with the highest level theoretical calculations shows agreement to within the estimated error.
Tập 96 Số 2 - Trang 919-926 - 1992
The laboratory microwave spectrum of the cyanide radical in its <i>X</i> 2Σ+ ground state The microwave absorption spectrum of the CN molecule in the v=0 and v=1 vibrational states of the electronic ground state has been obtained in glow discharges in nitrogen–cyanogen mixtures at room temperature. Zeeman modulation is used for detection of the signal, and the microwave source is phase locked and digitally programmed by a computer. For each vibrational state the frequencies of the seven strongest hyperfine components of the N=0→1 rotational transition have been extracted from a careful regression analysis of the complex line shapes observed in the digitized spectral data. For the v=0 state the resulting rest frequencies and molecular parameters are in good agreement with, but more precise and accurate than, the values obtained from earlier radioastronomical studies. For the excited vibrational state the present work provides the first determination of the hyperfine parameters. The precision of the results for both states is sufficient to give a reliable measure of the variation of the spin–rotation constant (γ) and the hyperfine constants (b, c, and eQq) with vibrational quantum number.
Tập 67 Số 9 - Trang 3956-3964 - 1977
Extension of the CN Red and Violet Band Systems The wavelengths and intensity distributions for the red (A 2Π→X 2Σ) and violet (B 2Σ→X 2Σ) bands which were observed in a mixture of active nitrogen and CH4 are given. Bands which originate in the A 2Π and B 2Σ states with excitation energies in the range 4.5-6 eV are well developed. The wavelength range studied was 3000-6700 Å. About 20 of the violet bands and 30 of the red bands have not been reported previously.
Tập 48 Số 5 - Trang 1980-1984 - 1968
Random sequential adsorption on partially covered surfaces The random sequential adsorption (RSA) approach was used to analyze adsorption of hard spheres at surfaces precovered with smaller sized particles. Numerical simulations were performed to determine the available surface function φl of larger particles for various particle size ratios λ=al/as and surface concentration of smaller particles θs. It was found that the numerical results were in a reasonable agreement with the formula stemming from the scaled particle theory with the modification for the sphere/sphere geometry. Particle adsorption kinetics was also determined in terms of the RSA simulations. By extrapolating the θl vs τ−1/2 dependencies, the jamming concentrations of larger spheres θl∞ were determined as a function of the initial smaller sphere concentration. It was found that θl∞ were considerably reduced by the presence of smaller sized particles, especially for λ≫1. The pair correlation function g of larger particles in the jamming state was also determined, showing more short range ordering (at the same θl) in comparison with monodisperse systems. The theoretical predictions stemming from our calculations suggest that the presence of trace amounts of very small particles may exert a decisive influence on adsorption of larger particles.
Tập 108 Số 23 - Trang 9851-9858 - 1998
Fluctuation of the number of adsorbed particles analyzed by a virial expansion: Comparison between experiment and theory The irreversible random adsorption of particles on a surface is guided by the available surface function φ. The relative fluctuation σ2/〈n〉 in the number of particles n in a finite region provides one characterization of the distribution of these particles on the surface. We show rigorously that the two quantities are given by the same expression to first order in the surface coverage, for any irreversible adsorption process. This is confirmed in two particular cases: for random sequential adsorption, where values for σ2/〈n〉 from numerical simulations can be compared to an analytic expression for φ, and for Ballistic deposition, where experimental values for deposition under a strong gravitational influence can also be compared to an existing analytical expression for φ.
Tập 102 Số 12 - Trang 5077-5081 - 1995