Volume 58, Issue 5-6

Ludwig Waldmann, who died on February 9th, 1980, would have become ninety years old on June 8th, 2003. On this occassion, a list of his scientific publications is presented here. To honour Professor Waldmann and to point out his contributions to the progress of science, some comments are made on his publications, after a few brief remarks on his biography.

The pure rotational spectra of [ 18 O]ketene, H 2 C=C 18 O, [1- 13 C]ketene, H 2 C= 13 CO, and [2- 13 C]ketene, H 2 13 C=CO, have been revisited in the frequency region 200 - 350 GHz in the ground vibrational state. From more than 100 R-branch transitions for each isotopomer a set of rotational and centrifugal distortion constants could be derived using the Watson S-reduction formalism. The values obtained for the rotational constants B and C agree very well with results of former investigations. The agreement is worse with respect to the A constants, but our newly determined A values agree well with the corresponding values of the main species and the 17 O isotopomer.

By means of the Bäcklund transformation, a quite general variable separation solution of the (2+1)- dimensional long dispersive wave equation: λq t + q xx − 2q ∫ (qr) x dy = 0, λr t − r xx + 2r ∫ (qr) x dy= 0, is derived. In addition to some types of the usual localized structures such as dromion, lumps, ring soliton and oscillated dromion, breathers soliton, fractal-dromion, peakon, compacton, fractal and chaotic soliton structures can be constructed by selecting the arbitrary single valued functions appropriately, a new class of localized coherent structures, that is the folded solitary waves and foldons, in this system are found by selecting appropriate multi-valuded functions. These structures exhibit interesting novel features not found in one-dimensions. - PACS: 03.40.Kf., 02.30.Jr, 03.65.Ge.

The local structure of the rhombic Co 2+ center in NaF crystal is investigated by using the perturbation formulas of electron paramagnetic resonance (EPR) gfactors gi(i = x,y, z) and hyperfine constants A i for a 3d 7 (Co 2+ ) ion in rhombic octahedral symmetry based on a cluster approach. In these formulas, the contributions from the admixture among different states, covalency effect as well as rhombic crystal field are included. By studying the EPR data of the rhombic Co 2+ center, one can reasonably obtain the local structural (or rhombic distortion) parameters ΔRc(≈ 0.268 Å) for the central Co 2+ and ΔR p (≈ 0.181 Å) for the two F − ions along [100] and [010] axes closest to the Na + vacancy V Na . The reasonableness of the results is also discussed.

The (CH 3 ) 2 ĊCOOH radical has been observed in the EPR spectra of γ-irradiated single crystals and powders of N-acetyl-α-aminoisobutyric acid and N-carbamyl-α-aminoisobutyric acid.

Rhyolite from the “Yellow Stone of Nevșehir” and γ-irradiated trona from the Ankara Mine have been investigated by electron paramagnetic resonance at ambient temperature and at 113 K. Rhyolite was examined by X-ray powder diffraction and found to consist mainly of SiO 2 . Before γ-irradiation, the existing paramagnetic species in rhyolite were identified as ṖO 4 2− , ĊH 2 OH, ĊO 3 − , ṠO 2 − , ĊO 3 3− , and ĊO 2 - free radicals and Fe 3+ at ambient temperature. At 113 K ṠO 2 - , ĊO 3 3- , and ĊO 2 − radicals and Fe 3+ were observed. The γ-irradiation produced neither new species nor detectable effects on these free radicals. The disappearance of some of the radicals at 113 K is attributed to the freezing of their motions. Before γ-irradiation, the trona mineral shows only Mn 2+ lines, but after γ-irradiation it indicated the inducement of ĊO 3 3− and ĊO 2 - radicals at ambient temperature, 113 K, in addition to the Mn 2+ lines. The g and a values of the species were determined.

The EPR spectra of the phosphorous centred radicals produced by γ-irradiated single crystals of three phosphorous compounds have been observed and identified as the free radicals (OCH 3 ) 2 ṖO and (OCH3)2PȮ.

The electron spin resonance (ESR) of Cr 3+ in K 1−x Tl x Al(SO 4 ) 2 ·12H 2 O has been studied at 300 K and 9.45 GHz. The ESR spectrum for x between 30 and 90% shows several chromium complexes. The variation of the zero-field splitting parameter D suggests that monovalent ions play an important role in the trigonal distortion of the water octahedron around the trivalent metal ion in alums. - PASC: 76.30 F.

Lithium has been electrochemically intercalated from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO 4 into graphite, and the lithium isotope fractionation accompanying the intercalation was observed. The lighter isotope was preferentially fractionated into graphite. The single-stage lithium isotope separation factor ranged from 1.007 to 1.025 at 25 °C and depended little on the mole ratio of lithium to carbon of the lithium-graphite intercalation compounds (Li-GIC) formed. The separation factor inceased with the relative content of lithium. This dependence seems consistent with the existence of an equilibrium isotope effect between the solvated lithium ion in the EC/MEC electrolyte solution and the lithium in graphite, and with the formation of a solid electrolyte interfaces on graphite at the early stage of intercalation.

Infrared spectroscopy has been used in adsorption studies of trimethyl phosphite (TMP) on the hydrogen (H) form of the A-type and 13X zeolites. Infrared spectra of H-zeolites, except H-KA, show that TMP reacts rapidly with silanol hydroxyls on their surfaces and gives rise to form product molecules such as SiOCH 3 and liquid dimethyl phosphite. The unaccomplished adsorption on the H-KA zeolite has been attributed to the occurence of stable KOH hydroxyls with not-exchanged K cations instead of SiOH hydroxyls on this zeolite.

The paper presents the results of viscosity measurements performed on 1,2-alkanediols, H(CH 2 ) n−2 CH(OH)CH 2 (OH), n = 2 : 12, and 1,n-alkanediols, HO(CH 2 ) n OH, n = 2 : 10, as functions of the temperature. It is shown that the viscosity (at constant temperature) and activation energy of the viscosity show a quite different dependence on the length of the alkane chain in 1,2- and 1,n-alkanediols molecules.

Viscosity measurements were performed for 1,2-pentanediol, CH 3 (CH 2 ) 2 CH(OH)CH 2 (OH), and 1,5-pentanediol, HO(CH 2 ) 5 OH, dissolved in water and 1-pentanol, in the whole range of concentration (x). The viscosity excess (η E ) of the solutions studied is negative with the exception of concentrated mixtures of the diols with water, where strong anomalies in the η E (x) dependence are observed.

Molecular orbital calculations at the B3LYP/6-311G(d) level were carried out to elucidate the lithium isotope effects accompanying chemical insertion of lithium from 1-methoxybutane solution containing lithium and naphthalene to graphite. The lithium atom between the graphene layers of graphite was modeled as lithium atoms in 1:1 complexes of lithium and simple aromatic hydrocarbons with condensed benzene rings. The 7 Li-to- 6 Li isotopic reduced partition function ratio (RPFR) was found to be a decreasing function of the number of benzene rings adjacent to the benzene ring above which the lithium atom was located, and was “saturated” at 1.04570 at 25 °C. The most plausible lithium species in the 1-methoxybutane solution was a lithium atom interacting with a naphthalene molecule and solvated by a 1-methoxybutane molecule in the contact ion pair manner. Its RPFR value was 1.07126 at 25 °C. The two RPFR values gave a single-stage separation factor of 1.024 for the lithium isotopes, which agreed well with the experimental value of 1.023.

For the first time the low frequency relaxation process in two smectic phases (smectic A and smectic C) was studied at elevated pressures with the aid of DTA and dielectric spectroscopy. The substance studied, 2-(4-hexyloxyphenyl)-5-octyl-pyrimidine (6OPB8 in short) exhibits the nematic (N) - S A - S C phase sequence. The p-T phase diagram was established with DTA. However, the S A - S C transition was not observed in the DTA, but could be detected by dielectric relaxation measurements. The dielectric relaxation time measured as function of temperature and pressure, τ ∥ (p,T), enabled us to calculate the activation volume, Δ # V =RT(∂lnτ /∂p) T , and activation enthalpy, Δ # H = R(∂lnτ /∂T −1 ) p . It was found that Δ # V(SA) > Δ # V(SC) and Δ # H(N) ≫ Δ # H(SA) > Δ # H(SC), indicating that the molecular rotations around the short axes are more feasible in the tilted SC than in the orthogonal S A phase.

Five phase transitions of [Cd(DMSO) 6 ](ClO 4 ) 2 have been detected by differential scanning calorimetry, namely the three reversible transitions: stable KIa ↔ stable KIb at TC4 = 242 K, due to a change of the crystal structure, metastable KII ↔ metastable KIII at T C3 = 318 K, and metastable KII ↔ overcooled K0 at T C2 = 347 K, one irreversible transition: KIa ↔ K0 at T C1 = 376 K, and melting at T t = 465 K. From the enthalpy changes of these transitions it can be concluded that K0 is a solid rotational phase and KII and KIII are most probably solid phases with a high degree of orientational disorder. The phases K0, KII, and KIII form an enantiotropic system, but they are metastable in relation to the phases KIa and KIb in the whole temperature range, so they form the monotropic system with them.

Dielectronic recombination (DR) cross sections and rate coefficients are calculated for the isonuclear sequence Fe Z+ , with Z = 21, 20, 19, 18, 17, and 16, in which L-shell (2p-) excitations are involved during the initial capture. Most of the dominant transitions with Δn ≠ 0, using angular momentum average (AMA) approximation, are considered. It is found that the states 3pnd and 3dnd contribute most to the rate coefficients. In addition, the rates are found to increase with increasing number of electrons in the ion, ( i. e. as Z decreases). Moreover, the rate coefficients, α DR , for the studied ions are found to peak around the same energy ( kT = 30 Ry). A semi-empirical formula for the total rates α is obtained for the 2p-excitation with Δn ≠ 0 in the case of Fe Z+ ions. On comparing both results, the explicit calculations and the results obtained from the semiempirical formula, good agreement is found. The available results for α DR may be considered as a database for future comparison with experimental and theoretical calculations. Comparison of our results with other results show the effect of the empirical rate formula.

Fifteen sodium salts of mono and di-substituted N-bromobenzene-sulphonamides of the configuration, 4-X-C 6 H 4 SO 2 NaNBr (where X = H; CH 3 ; C 2 H 5 ; F; Cl; Br; or NO 2 ) and i-X,j- YC 6 H 3 SO 2 NaNBr (where i-X, j-Y = 2,3-(CH 3 ) 2 ; 2,4-(CH 3 ) 2 ; 2,5-(CH 3 ) 2 ; 2-CH 3 ,4-Cl; 2-CH 3 ,5-Cl; 3-CH 3 ,4-Cl; 2,4-Cl 2 or 3,4-Cl 2 ) are prepared and characterised by measuring their infrared spectra in the solid state and NMR spectra in solution. The N-Br vibrational frequencies, ν N−Br of N-bromoarylsulphonamides vary in the range, 945 - 925 cm −1 , while the N-Cl vibrational frequencies, ν N−Cl , are observed in the range 950 - 927 cm −1 for the corresponding N-chloroarylsulphonamides. Asymmetric and symmetric SO 2 stretching vibrations appear in the ranges, 1391 - 1352 cm −1 and 1148 - 1131 cm −1 for the monosubstituted N-bromoarylsulphonamides, while for the disubstituted N-bromocompounds they absorb in the ranges 1391 - 1331 cm −1 and 1149 - 1121 cm −1 , respectively. The chemical shifts of aromatic protons and carbon-13 in all the N-bromoarylsulphonamides have been calculated by adding substituent contributions to the shift of benzene and compared with the observed values. The agreement between the calculated and experimental chemical shifts for different protons or carbon-13 is quite good.

Dielectric studies of 4-methoxy-4’-cyanobiphenyl (1 OCB) in the supercooled isotropic and nematic phases were performed with the aid of three set-ups covering the frequency range 10 kHz - 5 GHz. In the static measurements the nematic phase could be supercooled down to 25 K below the clearing point, whereas in the dynamic studies a 12 K range was covered in a single run. The relaxation times and activation enthalpies characterising the molecular rotations around the principal inertia moment axes were determined. The predictions of theories based on the assumption of the rod-like molecules are well applicable to the dielectric data obtained.

The synthesis and characterization of [Cu 2 (L 1 )(3,5 prz)] (L 1 =1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino) propan-2-ol) 1 and of [Cu 2 (L 2 )(3,5 prz)] (L 2 =1,3-Bis(2-hydroxy-bromosalicylideneamino) propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu 2 (L 1 )(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperaturedependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm −1 for 1 and 440 cm −1 for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Hückel Molecular Orbital (EHMO) calculations are also reported.

The EPR parameters (g factors g ∥ , g ⊥ and hyperfine structure constants A ∥ , A ⊥ ) of a tetragonal (C 4v ) Sm 3+ center in CaF 2 and SrF 2 crystals are calculated by considering the crystal-field Jmixing among the ground 6 H 5/2 , the first excited 6 H 7/2 and second excited 6 H 9/2 state multiplets. In the calculations the free-ion and crystal-field parameters of the tetragonal Sm 3+ -F − center obtained from polarized laser-selective excitation spectroscopy are used. The calculated results suggest that the tetragonal Sm 3+ -F − center is the Sm 3+ center found by later EPR measurements. The g factors g ∥ , g ⊥ and hyperfine structure constants A ∥ , A ⊥ of this EPR center are satisfactorily explained.

It is shown that the sexual proliferation of a chiral population leads much faster than exponentially to monochirality.