Optical absorption of molybdenum thin films between 0.32 and 5.50 eV: Interpretation in terms of energy band transitions

We report, between 0.32 and 5.50 eV, the optical conductivity of polycrystalline thin films of molybdenum. The films have been deposited in ultra high vacuum and the measurements have been carried out in situ. We observe two maxima at 2.75 and 4.0 eV and two shoulders at 1.85 and 5.1 eV. The structure is understood in terms of interband transitions, the conductivity is compared to a joint density of states histogram deduced from Petroff and Viswanathan energy bands.     

Isoperimetrische Ungleichungen für elastisch gebundene Membranen auf Dreiseiten und auf Vierseiten

Summary Some isoperimetric inequalities for vibrating membranes are extended to an elastically supported boundary, using conformal transplantation. A further inequality for fixed-free boundaries is given in section 3.     

Investigations on the formation of tracks in crystals

The minimal energy loss (dE/d ζ)_k [MeV cm²/mg] for the formation of a track in an insulator has been determined for mica, tourmaline, quartz glass, quartz crystal, lithium niobate and beryl. The investigations show that the (dE/d ζ)_k value of a track detector can be roughly estimated from the thermal conductivity of the given material.     

Interplay of metamagnetic and structural transitions in Ca2-xSrxRuO4

Metamagnetism in layered ruthenates has been interpreted as a novel kind of quantum critical behavior. In an external magnetic field, Ca_2-xSr_xRuO₄ undergoes a metamagnetic transition accompanied by a pronounced magnetostriction effect. In this paper we present a mean-field study for a microscopic model that naturally reproduces the key features of this system. The phase diagram calculated is equivalent to the experimental T-x phase diagram. The presented model also gives a good basis to discuss the critical metamagnetic behavior measured in the system.     

Chirality sensitive effect on surface states in chiral p-wave superconductors

We study the local density of states at the surface of a chiral p-wave superconductor in the presence of a weak magnetic field. As a result, the formation of low-energy Andreev bound states is either suppressed or enhanced by an applied magnetic field, depending on its orientation with respect to the chirality of the p-wave superconductor. Similarly, an Abrikosov vortex, which is situated not too far from the surface, leads to a zero-energy peak of the density of states, if its chirality is the same as that of the superconductor, and to a gap structure for the opposite case. We explain the underlying principle of this effect and propose a chirality sensitive test on unconventional superconductors.     

Threshold CID investigation of isomeric Cu(I) azabox complexes

An improved method for deconvoluting energy-resolved collision-induced dissociation cross sections yields ligand binding energies for organometallic complexes with substantially less prior information than before. Application to isomeric 2:1 complexes of azabox ligands with Cu(I) gives consistent results for the binding energies of the ligands to homo- and heterochiral complexes with pseudo-enantiomeric ligands for cases where previous deconvolution methods had failed to give satisfactory results.     

Kurze Totalsynthesen von (±)-Sativen und (±)-cis-Sativendiol

Short Total Syntheses of (±)-Sativene and (±)-cis-Sativenediol Our approach to (±)-sativene (7) and (±)-cis-sdtivenediol (9) involves: (a) reaction of 3-methylbutanoyl chloride with Et₃N/cyclopentadiene to give the endo-isopropyl-ketone 1 (here improved to 71%), (b) NBS bromination of 1 to a 5:1 mixture (87%) of the bromo-ketones 2 and 3 , (c) NFD-reaction sequence initiated by the attack of 1,2-butadienyl titanate (complex of 15 , obtained from 2-butine) on 2/3 to afford 52% of the brexenone derivative 4 (along with 8% of its epimer 16 ), (d) addition of dibromomethane to 4 forming 63% of the diene-alcohol 5 (along with 13% of the diene-carbaldehyde 38 ), and (e) carbenoid ring-expansion with MeLi applied to 5 resulting in 41% the diene-ketone 6 (along with 15% of a 1:3 mixture of the diene-ketones 32 and 33 ). Wolff-Kishner reduction of 6 led to 81% of (±)-sativene (7), when enough O₂ was present, but to 97% of the diene 8 in the strict absence of O₂. (±)-cis-Sativenediol (9) was obrained (86%) by OsO₄ hydroxylation of 8 . The brexenone derivatives 4 and 16 (6:1, 50%) were also produced when the NFD-reaction sequence was applied to the isomeric bromo-ketone mixture 13/13 (1:3). The latter was obtained by NBS bromination of 10 , which in turn was available by base epimerization of 1 , followed by destructive removal of unreacted 1 by repeated gas-flow thermolysis. An analogous (less convenient) route to (±)-sativene (7) passed through a series of dihydro compounds (the ene series) it started with the methylidene-ketone 36 , which was the product (97%) of a partial hydrogenation of 4 . Addition of dibromomethane to 36 led t 62% of the methylidene-alcohol 39 (along with a little tetracyclic ether 40 ). Carbenoid ring expansion of 39 with MeLi afforded ca. 42% of the methylidene-ketone 41 (along with 7% of the methylidene-ketone 43 or, under slightly different condition, along with 9% of the methylidene-ketone 42 and 10% of the methylidene-carabaldehyde 44 ). The methylidene-alcohol 39 and the methylidene-ketone 43 were also obtained by partial hydrogenation of 5 and 33 , respectively. Wolff-Kisher reduction converted 41 into (±)-sativene ( 7 99%); the same conditons applied to 42 afforded only ca. 8% 7 (along with three other hydrocarbons, one of them (ca. 21%) probably being (±)-copacamphene (45)). In the diene series, the two succeeding reactions ( 4→5 and 5→6 ) competed with the same side reaction, a rearrangement leading to the brendene-aldehyde 38. In the ene series, the corresponding dihydro-by-product 44 was found in the reacton 39→41 , but not during 36→39. These side reactons could largely be suppressed by keeping the reaction temperature low. An explanation is proposed.