Band 41, Heft 6

Using a semi-classical formalism which includes Debye shielding, Stark broadening parameters of various components within the 4 s 2 P - 4 p ´ 2 P 0 multiplet and the 4 p - 4 d ( 2 P 0 - 2 P, 2 D 0 - 2 P, 2 D 0 - 2 D) supermutiplet of Ar II are computed. We show that when various components of a multiplet (supermultiplet or transition array) are broadened inequally by an embedded closelying perturbing level, use of a perturber param eter cut-off at the Debye length can restrain the calculated differences between Stark widths within the multiplet.

Although refuted for a long time as a monstrosity, today’s concepts in elementary particle physics necessitate it on theoretical grounds: The existence of isolated elementary magnetic north- or south poles. If compared with a proton, the mass of such a monopole is estimated to be gigantic; comparable to that of an amoeba. Under the impact of the empirical success of unified gauge models, the search for monopoles has been steadily enforced with the aid of new detection methods.

Two new explicit finite difference schemes are proposed for certain operator field equations in a lattice.

A simple spin-flavor model for the substructure o f the 6 known quarks is proposed which is able to predict the correct Dirac magnetic moments if we interpret the quark masses as constituent masses. The addition of other degrees of freedom is proposed to facilitate the prediction of the correct mixing angles.

The finding o f Morokuma et al., that polarization rather than electrostatics determines the order of the protonaffinities of ammonia and its mono-, di-, and trimethyl-substituted derivatives, is compared with the results of semempirical methods. We used atomic polarizabilities, charges and geometries calculated by the MINDO /3-method to determine the polarization and the electrostatic part of the energy of interaction between an approaching proton and fourteen bases. Further we used the polarizability increments found by us recently, and those of Miller and Savchik in the calculation of the polarization part. Use of the MINDO/3-FP polarizabilities or the polarizability increments leads to polarization energies which correlate with the ab initio results o f Morokuma in an excellent or satisfying manner, respectively. Moreover the polarization energies calculated with the M IN D O /3-FP data are found to correlate with the protonaffinities of the amines under consideration. In accordance with the ab initio results cited above, the electrostatic part o f the interaction energy becomes more and more positive if one replaces the hydrogen atoms in ammonia by methyl or ethyl groups successively. The reason for this counterintuitive effect is analyzed in the case of ammonia and the methylamines.

The possibility of state prediction in deterministic chaotic systems, which are described by 1-D maps, is discussed in the light o f information theory. A quantity h(l) is defined which represents the production of uncertainty on a future state by the chaotic dynamics (intrinsic noise) after / time steps have passed. h(l) is related to the Lyapunov characteristic exponent. Moreover, the influence of the measuring process (overlappings o f mapped boxes o f state space partition) and external noise on the state predictability are investigated quantitatively.

Julia sets are self-similar separatrices of the coast-line type found in noninvertible 2-D maps. The same class of maps also generates hyperchaos (chaos with two mixing directions). Smale’s notion of a “nontrivial basic set” provides a connection. These sets arise when a chaotic (or hyperchaotic) attractor “explodes”. In the case of more than one escape route, this set becomes a “fuzzy boundary” (Mira). Its projection as the map becomes noninvertible (1-D ) is a “Julia set in 1 D ”. In the analogous hyperchaos case the 2-D limiting map contains a classical Julia set of the continuous type. An identically looking set can also be obtained within a non-exploded hyperchaotic attractor, however, as a “cloud”. Julia-like attractors therefore exist. The theory also predicts Mandelbrot sets for 4-D flows. Julia-like behavior is a new, numerically easy-to-test for property o f most nontrivial dynamical systems.

S (0 ) values of expanded alkali metals are calculated in random phase approximation. The results reproduce positive values of S (0) at sufficiently high temperatures showing the validity of RPA in one-component plasma systems.

The microwave ground state spectra of methylphosphine-borane-( 11 B) and methylphosphinetrideuteroborane-( 11 B) have been measured by microwave Fourier transform spectroscopy and analysed for 11 B-nuclear quadrupole hyperfine splittings and CH 3 and BH 3 torsion fine structure. As high J transitions were measured a centrifugal distortion analysis was necessary. The B-P bond order is discussed.

A powder X-ray diffractometer study of hexakis(tridecylsulfono)benzene (HASB13) has been carried out over the temperature range 20 to above 80 °C. In this range three phase transitions are observed by sharp discontinuities in the diffraction pattern indicating a solid-solid, solidmesophase, and mesophase-liquid transition. The mesomorphic phase is identified as a hexagonal columnar discotic mesophase, D hd , with intercolumnar spacing of 25.7 Å and average stacking distance of 4.9 Å. Both distances are independent of temperature but there appears to be a gradual increase in the stacking disorder as the temperature is increased. The magnitude of the intercolumnar distance suggests a considerable degree of side chain disorder. A detailed X-ray diffraction study was also performed at room temperature on a single crystal of hexakis(propylsulfono) benzene (HASB3), which is not mesogenic. The results provide detailed information on the structure of HASB 3 which is used in the interpretation of HASB 13 results.

Upper bounds for the total π-electron energy of benzenoid hydrocarbons, depending on the number of carbon atoms and carbon-carbon bonds, are examined and several of their properties established.

By activation of the new host lattices Ba 2 La 2 B 2+ Te 2 O 12 (B = Zn, Mg) with trivalent rare earth ions Ln 3+ = Pr. Sm, Eu, Tb, Dy, Ho, Tm an emission in the visible region is observed. The influence of the electronic structure and concentration on the relative emission efficiency as well as the host lattice participation in the energy transfer processes are discussed.

The electronic absorption spectra of the solid tetraalkylammonium salts of [OsF n Cl 6-n ] 2- , n = 0 -6 , including the stereoisomers for n = 2, 3, 4, are measured at 10 K. The strong bands in the UV/VIS region are assigned to charge-transfer transitions from π(t 1 u , t 2 u ) and σ (t 1 u ) Cl orbitals into the π (t 2g 4 ) Os(IV) level. The observed splittings and shifts are interpreted by qualitative MO treatment according to point groups D 4h , C 4v , C 3v and C 2v of the mixed complexes. The weak intraconfigurational transitions within the t 2g 4 configuration of Os(IV) are splitted by spin orbit coupling and lowered symmetry into multiplets with up to five states, observed in the NIR regions 4700-7300, 10 700-13 200 and 17 000-21 600 cm -1 . The O -O - transitions are deduced from vibrational fine structure; in some cases they are confirmed by electronic Raman bands with the same frequencies and by hot bands observed in the normal temperature spectra. Within the series of complexes all absorption bands are shifted systematically to higher energies with increasing number of F-ligands.

The isotopic dependence of the g-tensor of an asymmetric top molecule is investigated. A relationship is proposed which may be used to determine the g-tensor for isotopic species without measurements.

An attempt is made to derive an expression for the effective electron mass along the direction of a magnetic field in bismuth under magnetic quantization by using the generalized dispersion relation of the conduction electrons as proposed by Meclure and Choi. It is found that the oscillatory quantum number dependent behaviour of the effective electron mass at the Fermi level in bismuth is solely due to band non-parabolicity and is a characteristic feature of the above model.