In this paper, potential‐dependent transformations are used to transform the four‐component Dirac Hamiltonian to effective two‐component regular Hamiltonians. To zeroth order, the expansions give second order differential equations (just like the Schrodinger equation), which already contain the most important relativistic effects, including spin–orbit coupling. One of the zero order Hamiltonians is identical to the one obtained earlier by Chang, Pelissier, and Durand [Phys. Scr. 34, 394 (1986)]. Self‐consistent all‐electron and frozen‐core calculations are performed as well as first order perturbation calculations for the case of the uranium atom using these Hamiltonians. They give very accurate results, especially for the one‐electron energies and densities of the valence orbitals.

Relativistic regular two‐component Hamiltonians

We report on the determination of a high quality ab initio potential energy surface (PES) and dipole moment function for water This PES is empirically adjusted to improve the agreement between the computed line positions and those from the HITRAN 92 data base with J⩽5 for H216O The changes in the PES are small, nonetheless including an estimate of core (oxygen 1s) electron correlation greatly improves the agreement with the experiment Using this adjusted PES, we can match 30 092 of the 30 117 transitions in the HITRAN 96 data base for H216O with theoretical lines The 10, 25, 50, 75, and 90 percentiles of the difference between the calculated and tabulated line positions are −011, −004, −001, 002, and 007 cm−1 Nonadiabatic effects are not explicitly included About 3% of the tabulated line positions appear to be incorrect Similar agreement using this adjusted PES is obtained for the 17O and 18O isotopes For HD16O, the agreement is not as good, with a root-mean-square error of 025 cm−1 for line

/pdf/the-determination-of-an-accurate-isotope-dependent-potential-s0bhuuvvjo.pdf

The determination of an accurate isotope dependent potential energy surface for water from extensive ab initio calculations and experimental data

A mean-field spin-orbit method applicable to correlated wavefunctions

Mixed-valence (MV) compounds are excellent model systems for the investigation of basic electron-transfer (ET) or charge-transfer (CT) phenomena. These issues are important in complex biophysical processes such as photosynthesis as well as in artificial electronic devices that are based on organic conjugated materials. Organic MV compounds are effective hole-transporting materials in organic light emitting diodes (OLEDs), solar cells, and photochromic windows. However, the importance of organic mixed-valence chemistry should not be seen in terms of the direct applicability of these species but the wealth of knowledge about ET phenomena that has been gained through their study. The great variety of organic redox centers and spacer moieties that may be combined in MV systems as well as the ongoing refinement of ET theories and methods of investigation prompted enormous interest in organic MV compounds in the last decades and show the huge potential of this class of compounds. The goal of this Review is to give an overview of the last decade in organic mixed valence chemistry and to elucidate its impact on modern functional materials chemistry.

Organic mixed-valence compounds: a playground for electrons and holes.

An effective Hamiltonian for diatomic molecules . Ab initio calculations of parameters of HCl

Nonadiabatic dissociation energies are calculated for 619 vibration-rotation levels of the ground electronic state of HD+ using a transformed Hamiltonian and an artificial-channels scattering method. In particular, coupling of rotational and electronic angular momenta is accounted for, so that levels with high N may be studied. Relativistic and radiative corrections are added to give dissociation energies, from which calculated transition energies may be compared with the experimentally available values; the agreement is good, in most cases to within experimental error (0·001 cm-1).

Calculations for vibration-rotation levels of HD+, in particular for high N

Hexahydropyrimidines N,N-bridged by a chain of n methylene groups (1,(n+2)-diazabicyclo[n.3.1]alkanes) adopt out,out (axial,axial) structures for n=2, 3, and 4. When n=5, the photoelectron spectrum shows evidence of the presence of some of the out, in (axial,equatorial) isomer in the gas phase, although none can be found in solution. When n=6, the compound is apparently entirely out,in in the gas phase but exists as a mixture of out,out and out,in conformers in solution. For n=1, only the diamond lattice out,in isomer can be detected in solution. These experimental data are correlated with force field (MM2) calculations; multiple minimum search methods have been used to locate all low-energy conformations

The out,out to out,in Transition for 1,(n+2)-Diazabicyclo[n.3.1]alkanes

A complete hamiltonian for a translating, rotating, vibrating molecule in the presence of a constant external electromagnetic field is derived starting with the Breit equation reduced to a non-relativistic form, correct to order c -2. A number of new terms appear, which have not been obtained in less precise derivations. These include mass polarization corrections to the orbital Zeeman, spin-orbit and orbit-orbit interactions together with spin-vibration, orbit-vibration and orbit-rotation interactions. In addition there is a vibrational Zeeman interaction which in certain circumstances may be of the same order of magnitude as rotational Zeeman terms. The final hamiltonian provides a starting point for future investigations of the possible effects of these new interactions on the microwave and radiofrequency spectra of both open and closed-shell molecules.

The molecular hamiltonian: I. Non-linear molecules

An optical fibre sensor is described which is sensitive to potassium ions in aqueous solution in the concentration range 10–3–10–1M.

Communication. An optical potassium ion sensor

An artificial-channels scattering method (M. Shapiro and G. G. Balint-Kurti, J. Chem. Phys. 71, 1461 (1979)) is used with a transformed Hamiltonian (R. E. Moss and I. A. Sadler, Molec. Phys. 66, 591 (1989)) to calculate the energies of vibration-rotation levels for the ground electronic state of HD{sup +}. All nonadiabatic effects, except for part of the coupling of rotational and electronic angular momenta, are accounted for. The results, which are for {ital v}=0--21, {ital J}=0,1, together with some other levels involved in observed transitions, are compared with previous calculations, particularly those of Wolniewicz and Poll (Molec. Phys. 59, 953 (1986)). Inclusion of a correction to the energies of {ital J}{ne}0 levels to allow for the remaining contribution of {Pi} electronic states permits comparison with experimental transition energies. The agreement is excellent.

Calculations of vibration-rotation energy levels of HD+

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