摘要:

AbstractCurrent aspects of the field of research are summarized, as defined by the title of this article and the theme of the related, recent discussion meeting, which is the subject of this special issue of Berichte der Bunsengesellschaft für Physikalische Chemie

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990302

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the emission spectrum of molecular hydrogen the Rydberg‐Rydberg bands of type nsσg−2pσu,πuare an order of magnitude weaker than the corresponding bands with ndσgupper states. We have calculated the dipole moment functions for the electronic1Σg+−1Σu+and1Σg+‐1Πutransitions whose upper states at small inter‐nuclear distances are of 2s, 3s, 3dσ, 4s, and 4dσ character, with lower states 2pσB, 3pσB', 4pσB”1Σu+, 2pπC, and 3pπD1Πu. The results confirm that the transitions of s–p character are much weaker than the d‐p ones. We have also obtained improved Born‐Oppenheimer electronic energy curves and adiabatic energy corrections for the lowest four1Σu+and two1Πustates, and nonadiabatic coupling functions among the four1Σu+states. In theB1Σu+state the theoretical term values of the lowest rovibronic levels agree, after correction for nonadiabatic and relativistic energy shifts, with spectroscopic measurements in H2and D2within the combined uncertainties of the experiments and of the small

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990303

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractA new method for calculating rotation‐vibrational states of triatomic molecules is presented. It is based on an expansion of the wavefunction in terms of hyperspherical harmonics, which cover five coordinates, and numerical integration of the resulting set of differential equations in the remaining coordinate, the hyperradius ρ. The method is applied to H3+. Here we compare the results for two electronic surfaces, the Meyer‐Botschwina‐Burton surface and the new surface by Kutzelnigg and cow

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990304

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractA matrix approach is proposed for calculating term energies and wavefunctions of rovibronic levels in diatomic molecules with strongly coupled electronic states. The interaction matrix is set up in a basis of uncoupled rovibronic functions of Hund's case (a) type. Its diagonalization yields directly term energies and the corresponding wavefunctions. This approach has been applied to calculate the rovibronic spectra of NiH and NiD, typical unsaturated transition metal compounds, which exhibit three low‐lying electronic states,2Δ,2∏, and2Σ+. Spinorbit and rotational interactions have been taken into account in this case. Eigenvectors obtained from diagonalizing theJ‐dependent interaction matrices exhibit strong mixing between2∏3/2, νn+1and2Δ3/2, νnbasis functions and between2Σ+, νnand2∏1/2, νn. The low‐lying states of NiH and NiD can therefore be regarded as belonging to Hund's case (c) coupling. For total angular momentum quantum numbersJup to 5.5 (7.5 is some cases) Ω‐splittings are presented. Very good agreement is observed with various measurements and with predictions from a super‐muliplet fit to experimental data, showing that the proposed method is applicable also in cases where the usual formulae for calculating Λ‐doublings derived from doub

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990305

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Zeeman splitting of rotational lines in the V system of CS2were systematically studied, using a cw single mode frequency doubled dye laser with linear and circular polarization in a cold collimated molecular beam within a tunable magnetic field up to 0.2 Tesla. Two sources of magnetic moments of levels in the excited1B2state could be identified. First, a second order spin‐orbit spin‐rotational coupling to the spin components of the3A2(3Δu) electronic state is responsible for the generated magnetic moments in the rotational levels of the1B2state, which seem to be irregularly behaved. Because of the insufficient information about the spin components of the triplet state3A2(3Δu) we developed a model of two interacting levels, which can explain many of the observed patterns of the rotational levels in a magnetic field. Secondly, an electronic Coriolis coupling (Renner‐Teller coupling) betwen the two Born‐Oppenheimer component states1A2(1Δu) and1B2(1Δu) leads to a partly quenched electronic orbital angular momentum. Consequently, the LandégJfactors posses a {J(J+1)}−1dependence. This has been observed for the π bands of the1B2(1Δu) state. Moreover, the analysis of the measured Zeeman patterns yields valuable information about the cou

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990306

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractThe pure rotational spectrum in the far‐infrared and its absolute intensity in the vibrational ground state of CH2D2and CHD3were measured by high‐resolution interferometric Fourier transform techniques. The analysis of the integrated absorption cross sections results in a permanent, vibrationally induced electric dipole moment |μ0| = (8.6 ± 1.4)·10−3Debye for CH2D2. This value is much more reliable than the older value existing in the literature and is also in much better agreement with our previously published theoretical estimate (μ0= ‐(7.60±0.50)·10−3Debye, the z‐axis being the C2axis with sign chosen such that the H‐atoms have posi

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990307

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractThe FCCC1 molecule has been studied by ab initio methods and high resolution IR spectroscopy. Employing a TZ2Pf basis set the quadratic, cubic, and quartic force fields have been determined at the SCF and MP2 levels, and the equilibrium structure has been calculated. The vibrational and rovibrational parameters deduced from the force fields have guided the analysis of high resolution FTIR spectra of FCCC1 in the v1, v2, 2v4and v4v5regions. Therefrom, ground, v4= 1 and v5= 1 rotational parameters have been determined by means of lower state combination differences. The 2v4(Σ+) and v4v5(Σ+and Δ) levels have been analyzed in detail, and anharmonic perturbations disclosed with the help of the ab initio results. The available experimental data are in excellent agreement with the ab initio predictio

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990308

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractMost of the anharmonic constants of trichlorosilane and ‐methane have been determined, with special emphasis to the values ofx1i,i= 1 to 6. In both molecules, there is a strong Fermi resonance between hydrogen stretch and bend vibrations and Coriolis interaction between ν2and ν5. Some irregularities in the hot band structures point to an interaction of ν1with ν2+ 2ν4and other higher order interactions. In SiHCl3,x13andx16are near 0, in agreement with a rule that nondiagonal anharmonicities between high‐ and low‐frequency vibrations tend to be small. In CHCl3, the corresponding values are larger, though still small. We discuss a possible correlation of such values with the frequency change of one of the vibrations, if the bond corresponding to the other one is dissociated. Ni(CO)4is quoted as a further example. The data set could help in calculations of vibrational relaxa

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990309

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractWe adopt the theory of intramolecular dynamics to explore charge separation and recombination in two classes of ‘isolated’ solvent‐free molecular systems: (A) Supermolecules containing bridged electron donor and electron acceptor, where electron transfer occurs on a spatial scale of ≈︁ 10 Å. (B) Ultrahigh molecular Rydberg excitations with a principle quantum numbern≃ 50−300 and spatial dimensions of ≈︁ 104Å, where relaxation processes, e.g., electron‐core recombination via internal conversion or predissociation, and charge separation by autoionization, are manifested. The molecular limit for photoinduced long‐range ET in isolated supermolecules [class (A)] is treated on the basis of the statistical limit for interstate radiationless transitions, which involve either a direct or a mode‐selective mediated coupling. The level structure, optical excitation modes and dynamics of high molecular Rydbergs [class (B)]interrogated by time‐resolved ZEKE (zero‐electron kinetic energy) spectroscopy, are treated by the effective Hamiltonian formalism. We pursue the formal analogy between the coupling, accessibility and decay of ultrahigh Rydbergs in an external weak (F= 0.01−1.0 V/cm) electric field and intramolecular (interstate and intrastate) relaxation in a bound level structure. Model calculations for the field‐induced (l) mixing reveal that the Rydberg dynamics is characterized by two distinct (≈︁ ns and ≈︁μs) time scales. Up to date, long time‐resolved (10 μs − 100 ns time scales) nonexponential decay of ZEKE Rydbergs was experimentally documented, in accord with our analysis. The predicted existence of the short decay times (1 − 10

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990310

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY

摘要:

AbstractAn iterated map which mimics the dynamics of a high Rydberg electron revolving around an anisotropic ionic core is described. The map specifies the change in the quantum numbers of the electron due to its passage near to the rotating core. Attention is centered on the limiting case of physical interest where the rotation of the core is faster than the orbital motion of the electron. While the map does provide for a very efficient way to numerically simulate the motion, its main advantage is in that it delineates the various dimensionless coupling parameters that govern the dynamics. To make contact with many experiments, external electrical and magnetic fields are included in the Hamiltonian. The stretch of the kinetic time axis due to the presence of external fields is discussed. The full map can be further approximated by a one‐dimensional map which captures the essence of the dynamics. The primary aspects having to do with the three‐dimensional character of the actual motion are incorporated in the magnitude of the dimensionless coupling parameters. A simple but realistic limit of the one‐dimensional map is discussed which can be considered as the electron undergoing diffusion in its energy. The mean first passage time out of the detection window and the branching fractions for ionization vs. stabilization of the electron are computed in the diffusion approximation. As is experimentally observed, the lifetime of the high Rydberg states exhibits a maximal value when plotted vs. the e

ISSN:0005-9021    

DOI:10.1002/bbpc.19950990311

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1995

数据来源: WILEY