Stark spectroscopy of high-lying odd parity levels in atomic samarium

We have performed a series of experiments to observe 11 Stark-induced E1 transitions from the 15650.55 cm^-1 level to higher levels with odd parity in samarium (Sm) with optical double-resonance technique. Five Stark-induced E1 transition to the 28233.08, 28613.22, 28913.97, 29041.31 and 29130.03 cm^-1 levels have been observed. In order to investigate the contributors to the Stark-induced E1 transition, we have measured scalar and tensor polarizabilities for the observed Stark-induced E1 transitions. Clear Stark splittings were observed for the levels 28233.08 and 28613.22 cm^-1, and their tensor polarizabilities were determined for each isotope. Scalar polarizabilities were determined for the 28233.08, 28613.22, 28913.97 and 29130.03 cm^-1 levels for the first time. Among them, scalar polarizability for the 28233.08 cm^-1 level was the largest in magnitude and was 3.60(10) x 10³ kHz/(kV/cm)² for Sm. We noticed that both scalar and tensor polarizabilities of the 28233.08 cm^-1 level depend on the isotope; the difference of magnitude of the scalar and tensor polarizabilities between Sm and Sm were remarkably large and were about 10 and 6 percent, respectively.Received: 10 February 2003, Published online: 30 July 2003PACS: 32.60.+i Zeeman and Stark effects - 32.10.Dk Electric and magnetic moments, polarizabilityD. Angom: Present address: Physical Research Laboratory, Navarangpura, Ahmedabad 380 009, India.     

The decomposition of curvature netted hypersurfaces

We define the concept of a curvature netted hypersurface and investigate in what case the hypersurface is covered by a twisted product of spheres (or topological product of spheres). All hypersurfaces in a space form such that the number of mutually distinct principal curvatures is constant (i.e. each principal curvature has constant multiplicity) are curvature netted hypersurfaces. Also, we state some inductive constructions of the hypersurfaces, where we use the discussion related to the tube.     

Bounds to the wave-vector dependent susceptibility of the ising model

It is shown that rigorous upper and lower bounds to the wave-vector dependent susceptibility of the Ising Model are obtained either when an upper bound to the spin pair correlation function and a lower bound to the susceptibility at zero wave-vector are given, or when a lower bound to the former and an upper bound to the latter are given. An example of the numerical computation of the bounds is presented for the Ising model on the sc lattice.     

On the bethe approximation for the random bond Ising model

A random bond Ising model is considered in terms of the pair approximation, which is equivalent to the Bethe approximation, of the cluster variation method. On taking the configurational average over the random distribution of bonds ±J, we take into account the nearest neighbor correlations between effective fields and bonds. We investigate their effects to the phase transition temperature from the paramagnetic phase to the ferro- (or antiferro-) magnetic phase and to the spin glass phase for the Ising model on the square lattice. It turns out that the correlation effects act favorably to the spin glass phase and bend upward the line of transition temperature from the paramagnetic phase to the spin glass phase as the concentration being apart from 0.5. In the appendix, we derive the expression of free energy in the weak interaction limit.     

Syntheses of polycyclic-1,4-dithiines and related heterocycles

Reactions of dihalogenoquinones or dihalogenoquinoxalines with thioamides gave the corresponding 1,4-dithiines in high yields. Many of polycyclic 1,4-dithiin derivatives can be synthesized by the reactions of dihalogenoheterocycles with thioamides, and they are useful as pigments and functional materials for electro-optical applications. Some of heteroaromatic-1,4-dithiins formed an intermolecular charge-transfer (CT) complex with a π-acceptor such as TCNQ, and they are useful as π-donors for CT complex.     

Long-term operation of CsLiB(6)O(10) at elevated crystal temperature

We have successfully resolved the degradation problem of CsLiB(6)O(10) (CLBO) by means of elevated crystal temperature. CLBO crystals were continuously operated at 160 degrees C in ordinary room humidity. No degradation of performance was observed after more than 1 month. We believe that heating CLBO crystal above 130 degrees C can relieve stresses introduced by crystal hydration, cutting, polishing, and thermal shock owing to laser power absorption. Thus long-term operation of CLBO crystal is achieved for effective application of laser frequency conversion. Output stability from CLBO is also further enhanced at elevated crystal temperature.     

Spectral-linewidth broadening in synchronous Raman fiber amplification caused by cross-phase modulation effects and its suppression

When coherent light is amplified by a synchronous Raman fiber amplifier pumped by output pulses from a high-power erbium-doped fiber amplifier operating in an unsaturated gain regime, the detection efficiency with the heterodyne method is degraded. This degradation is caused mainly by cross-phase modulation effects. It is confirmed that using power-flattened pump pulses can suppress these effects.     

Reversible Dimerization and Polymerization of a Janus Diradical To Produce Labile C−C Bonds and Large Chromic Effects

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ‐dimers and σ‐polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C?C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain the variety of final products starting with structurally very similar reactants. These reversible reactions, covering an unusual regime of weak covalent supramolecular bonding, yield products which might be envisaged as novel molecular and polymeric soft matter phases.